Project Gutenberg's The Standard Electrical Dictionary, by T. O'Conor Slone This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.net Title: The Standard Electrical Dictionary A Popular Dictionary of Words and Terms Used in the Practice of Electrical Engineering Author: T. O'Conor Slone Release Date: September 5, 2008 [EBook #26535] Language: English Character set encoding: UTF-8 *** START OF THIS PROJECT GUTENBERG EBOOK THE STANDARD ELECTRICAL DICTIONARY *** Produced by Don Kostuch [Transcriber's Notes] Obvious spelling errors have been corrected. I have not reconciled the variety of spellings of names and other words. Obvious factual errors, typographical errors, discoveries made after 1892, and contemporary (2008) theories and use of words are noted in the text within square brackets. I have not researched and checked every assertion by the author. This book was published 5 years before discovery of the electron. See the labored and completely inaccurate explanations of aurora and "energy, atomic". The author and his contemporaries were like fifteenth century sailors. They had a good idea of their latitude and direction (Ampere, Kirkoff, Maxwell, Gauss, Faraday, Edison, …), but only the vaguest notion of their longitude (nuclear structure, electrons, ions). Altitude (special relativity, quantum theory) was not even imagined. Some relevant dates: Franklin's Kite--1752 Faraday's Law of Induction--1831 Maxwell's Equations--1861 Edison's Phonograph--1877 Edison's light bulb--1879 Edison's first DC power station--1882 Michelson-Morley experiment disproving ether--1887 Hertz demonstrates radio waves--1888 Westinghouse first AC power station--1891 This book--1892 Discovery of the electron--1897 Marconi radio signals cross the English Channel--1897 First Vacuum Tube--1904 Special Relativity, photo-electric effect explained with photons--1905 General Relativity: space-time dilation and curvature--1915 Confirmation of general relativity's prediction of the deflection of starlight by the Sun--1919 Discovery of the proton--1920 Quantum theory--1926 Discovery of neutron--1932 First transistor--1947 Soviet satellite Luna measures solar wind--1959 Edward M. Purcell explains magnetism with special relativity--1963 Purcell's explanation of magnetism as a result of Lorentz contraction of space along the direction of a current is a welcome relief from the convoluted descriptions in this book. Mathematical notation is rendered using "programming" notation. ^ Power--Exponential; A^3 means "A cubed" * Multiply / Divide + Add - Subtract ( ) Precedence--Perform before enclosing expression 2E6 Scientific Notation (2,000,000) A --------------------- 4.452 X 10^12 X t is rendered as A / ( 4.452E12 * t ) Where the rendering of a mathematical expression is in doubt, an image of the original text is included. Here are some definitions absent from the text. Foucault currents. Eddy currents. inspissate To thicken, as by evaporation. riband Ribbon. sapotaceous Order Sapotace[ae] of trees and shrubs, including the star apple, the Lucuma, or natural marmalade tree, the gutta-percha tree (Isonandra), and the India mahwa, as well as the sapodilla, or sapota, after which the order is named. Don Kostuch, MS, Electrical Engineering. [End Transcriber's notes.] WORKS OF T. O'CONOR SLOANE, A.M., E.M., Ph.D. ARITHMETIC OF ELECTRICITY A MANUAL OF ELECTRICAL CALCULATIONS BY ARITHMETICAL METHODS. Third Edition. Illustrated. $1.00. It is very useful to that class of readers to whom Algebra is a comparatively unknown quantity, and will meet its wants admirably.--Electrical World. ELECTRICITY SIMPLIFIED. A POPULAR TREATMENT OF THE SUBJECT. Illustrated. $1. 00. We especially recommend it to those who would like to acquire a popular idea of the subject.--Electric Age. ELECTRIC TOY MAKING. FOR AMATEURS. INCLUDING BATTERIES, MAGNETS, MOTORS, MISCELLANEOUS TOYS, AND DYNAMO CONSTRUCTION. Fully Illustrated. $1.00. THE STANDARD ELECTRICAL DICTIONARY. A POPULAR DICTIONARY OF WORDS AND TERMS USED IN THE PRACTICE OF ELECTRICAL ENGINEERING. BY T. O'CONOR SLOANE, A.M., E.M., Ph.D. NEW YORK GEORGE D. HURST PUBLISHER Copyright 1892 by NORMAN W. HENLEY & CO. PREFACE The purpose of this work is to present the public with a concise and practical book of reference, which it is believed will be appreciated in this age of electricity. The science has expanded so much that the limits of what may be termed strictly a dictionary of the present day would a few years ago have sufficed for an encyclopedia. It follows that an encyclopedia of electricity would be a work of great size. Yet a dictionary with adequate definitions, and kept within the closest limits by the statement of synonyms, and by the consigning of all the innumerable cross-references to a concise index will be far more than a mere dictionary in the ordinary sense of the term. Duplication of matter is to be avoided. This makes many definitions appear short. Yet, by the assistance of the reader's own general knowledge, and by referring to the very complete index, almost any subject can be found treated in all its aspects. There are exceptions to this statement. So much has been done in the way of mechanical detail, so many inventions in telegraphy and other branches have sprung into prominence only to disappear again, or to be modified out of recognition, that to embody descriptions of many ingenious and complicated apparatus has been absolutely impossible for want of space. A word as to the use of the book and the system of its construction may be given here. Each title or subject is defined once in the text. Where a title is synonymous with one or more others the definition is only given under one title, and the others appear at the foot of the article as synonyms. It may be that the reader is seeking the definition of one of these synonyms. If so a reference to the index shows him at once what page contains the information sought for. The use of an index in a work, necessarily of an encyclopedic form, will be appreciated by all users of this book. vi PREFACE. Where a title embraces several words, all orders of the words will be cited in the index. To make the operation of finding references easy this rule has been carried out very fully. It is customary to regard electricity as a growing science. It is unquestionably such, but the multiplication of terms and words is now not nearly so rapid as it has been, and the time for the compiling of a work of this character seems most propitious. It is hoped that the public will indulgently appreciate the labor it has entailed on all concerned in its production. SYMBOLS AND ABBREVIATIONS. adj. Adjective. v. Verb. q.v. "Which see.' / A mark of division, as A/B, meaning "A divided by B." ./. The same as above. [Transcriber's note: / will be substituted for this divide symbol.] = A mark of equality, meaning "is equal to." X A mark of multiplication, meaning "multiplied by." [Transcriber's note: * will be substituted for this divide symbol.] Fractional exponents indicate the roots expressed by their denominators and the powers expressed by their numerators. Thus, A^1/2 means the "square root of A;" A^1/3 means the "cube root of A;" B^3/2 means the "square root of the cube or third power of B." The use of powers of ten, as 10^10, 10^11, as multipliers, will be found explained at length in the definition "Ten, Powers of." vii STANDARD ELECTRICAL DICTIONARY A. Abbreviation for anode, employed in text relating to electro-therapeutics. It is sometimes written An. Abscissa. In a system of plane co-ordinates (see Co-ordinates) the distance of any point from the axis of ordinates measured parallel to the axis of abscissas. In the cut the abscissa of the point a is the line or distance a c. Fig. 1. AXES OF CO-ORDINATES. Absolute. adj. In quantities it may be defined as referring to fixed units of quantity, and it is opposed to "relative," which merely refers to the relation of several things to each other. Thus the relative resistance of one wire may be n times that of another; its absolute resistance might be 5 ohms, when the absolute resistance of the second wire would be 5/n ohms. A galvanometer gives absolute readings if it is graduated to read directly amperes or volts; if not so graduated, it may by "calibration" q. v. be made to do practically the same thing. 8 STANDARD ELECTRICAL DICTIONARY. Absolute Measurement. Measurement based upon the centimeter, gram, and second. (See Centimeter-Gram-Second System.) Absolute Temperature. Temperature reckoned from absolute zero (see "Zero, Absolute"). It is obtained by adding for the centigrade scale 273, and for the Fahrenheit scale 459, to the degree readings of the regular scale. Absorption, Electric. A property of the static charge. When a Leyden jar is being charged it dilates a little and the capacity increases, so that it can take a little more charge for a given potential difference existing between its two coatings. This phenomenon occurs with other static condensers, varying in degree with the dielectric. With shellac, paraffin, sulphur and resin, for instance, the absorption is very slight; with gutta-percha, stearine, and glass, the absorption is relatively great. The term is due to Faraday. Iceland spar seems almost or quite destitute of electric absorption. A. C. C. Symbol of or abbreviation for "anodic closure contraction" q. v. Acceleration. The rate of change of velocity. If of increase of velocity it is positive; if of decrease, it is negative. It can only be brought about by the exercise of force and is used as the measure of or as determining the unit of force. It is equal to velocity (L/T) imparted, divided by time (T); its dimensions therefore are L/(T^2). The c. g. s. unit of acceleration is one centimeter in one second. [Transcriber's note: The unit of acceleration is "centimeters per second per second."] Accumulator. (a) A term sometimes applied to the secondary or storage battery. (See Battery, Secondary.) (b) See Accumulator, Electrostatic (c) See Accumulator, Water Dropping. (d) See Wheel, Barlow's Accumulator, Electrostatic. Two conducting surfaces oppositely placed, and separated by a dielectric and arranged for the opposite charging of the two surfaces, constitute an accumulator, sometimes termed a condenser. As this arrangement introduces the element of a bound and of a binding charge, the electrostatic capacity of such is greater than that of either or of both of its component surfaces. The thinner the dielectric which separates the conducting surfaces, and the larger the surfaces the greater is the capacity; or the less will be the potential difference which a given charge will establish between its two coatings. The nature of the dielectric also determines its capacity. (See Capacity, Specific Inductive.) 9 STANDARD ELECTRICAL DICTIONARY. Fig. 2. SIR WILLIAM THOMSON'S WATER-DROPPING ACCUMULATOR. Accumulator, Water Dropping. This is also known as Sir William Thomson's Water-Gravity Electric Machine. It is an apparatus for converting the potential energy of falling water drops, due to gravity, into electric energy. Referring to the illustration, G represents a bifurcated water pipe whose two faucets are adjusted to permit a series of drops to fall from each. C and F are two metallic tubes connected by a conductor; E and D are the same. Two Leyden jars, A and B, have their inner coatings represented by strong sulphuric acid, connected each to its own pair of cylinders, B to D and E, and A to F and C. The outer coatings are connected to earth, as is also the water supply. One of the jars, say A, is charged interiorily with positive electricity. This charge, C and F, share with it, being in electric contact therewith. Just before the drops break off from the jet leading into C, they are inductively charged with negative electricity, the positive going to earth. Thus a series of negatively excited drops fall into the metal tube D, with its interior funnel or drop arrester, charging it, the Leyden jar B, and the tube E with negative electricity. This excitation causes the other stream of drops to work in the converse way, raising the positive potential of F and C and A, thus causing the left-hand drops to acquire a higher potential. This again raises the potential of the right-hand drops, so that a constant accumulating action is kept up. The outer coatings of the Leyden jars are connected to earth to make it possible to raise the potential of their inner coatings. In each case the drops are drawn by gravity into contact with objects similarly excited in opposition to the electric repulsion. This overcoming of the electric repulsion is the work done by gravity, and which results in the development of electric energy. 10 STANDARD ELECTRICAL DICTIONARY. Acidometer. A hydrometer or areometer used to determine the specific gravity of acid. They are employed in running storage batteries, to determine when the charging is completed. (See Areometer.) Aclinic Line. A terrestrial element; the locus on the earth's surface of no inclination of the magnetic needle; the magnetic equator. (See Magnetic Elements.) Acoustic Telegraphy. The system of sound-reading in telegraphy, universally used in the Morse system. The direct stroke of the armature of the electro-magnet and its "back stroke" disclose to the ear the long and short strokes, dots and lines, and long and short spaces as produced by the dispatcher of the message. In the Morse system a special magnet and armature is used to produce the sound called the "sounder;" in other systems, e. g., Steinheil's and Bright's apparatus, bells are used. (See Alphabets, Telegraphic.) Acoutemeter. A Hughes audiometer or sonometer applied to determining the quality of a person's hearing (See Hughes' Induction Balance,--Audiometer). The central coil by means of a tuning fork and microphone with battery receives a rapidly varying current tending to induce currents in the other two coils. Telephones are put in circuit with the latter and pick up sound from them. The telephones are applied to the ears of the person whose hearing is to be tested. By sliding the outer coils back and forth the intensity of induction and consequent loudness of the sounds in the telephones is varied. The position when the sounds grow so faint as to be no longer audible, gives the degree of delicacy of the person's hearing. By using a single telephone the same apparatus affords a means of testing the relative capacity of the right and left ears. 11 STANDARD ELECTRICAL DICTIONARY. Actinic Rays. The rays of light at the violet end of the spectrum; also the invisible rays beyond such end, or the ether waves of short periods which most strongly induce chemical change. Actinism. The power possessed by ether waves of inducing chemical change, either of decomposition or of combination. The violet and ultra-violet end of the spectrum of white light, generally speaking, represent the most highly actinic rays. Actinometer, Electric. Properly an apparatus for measuring the intensity of light by its action upon the resistance of selenium. A current produced by fixed electro-motive force passing through the selenium affects a galvanometer more or less according to the intensity of the light. It is more properly an electric photometer. The term has also been applied to a combination of a thermo-electric pile and galvanometer, the light falling on the pile affecting the motions of the galvanometer. Action, Local. (a) The wasteful oxydation of the zinc in a galvanic battery due to local impurities and variations in the composition of the zinc. These act to constitute local galvanic couples which cause the zinc to dissolve or oxydize, without any useful result. Amalgamation of the zinc prevents local action. Chemically pure zinc is also exempt from local action, and can be used in an acid battery without amalgamation. (See Amalgamation.) (b) The same term has been employed to indicate the eddy or foucault currents in dynamo electric machines. (Sec Current, Foucault.) Activity. The rate of doing work; the work done per second by any expenditure of energy. The activity of a horse-power is 550 foot lbs. per second, or 746 volt-coulombs per second. The practical electric unit is the volt-ampere, often called the watt. (Sec Energy, Electric.) Adapter. A screw coupling to engage with a different sized screw on each end; one of the uses is to connect incandescent lamps to gas-fixtures. A. D. C. Abbreviation for Anodic Duration Contraction, q. v.; a term in electro-therapeutics. Adherence, Electro-magnetic. The adherence between surfaces of iron due to elcctro-magnetic attraction. It has been applied to the driving-wheels of an engine and rail, whose grip is increased by such action. In one method a deep groove was cut around the wheel which was wound with a magnetizing coil. Thus one rim becomes a north and the other a south pole, and the rail completing the circuit acts as the armature. Such an arrangement prevents a wheel from sliding. Electro-magnetic adherence has also been employed to drive friction gear wheels. In one arrangement the two wheels are surrounded by a magnetizing coil, under whose induction each attracts the other, developing high adherence between their peripheries. 12 STANDARD ELECTRICAL DICTIONARY. Fig. 3. ELECTRO-MAGNETIC CAR WHEEL. Fig. 4. ELECTRO-MAGNETIC FRICTION GEAR. Admiralty Rule of Heating. The British Admiralty specifications for the permissible heating of dynamos. It holds that at the end of a run of six hours no part of the dynamo under trial shall show a rise of temperature greater than 11º C. (20º F.) above the temperature of the air surrounding it. This is thought to be a very stringent and unnecessarily high requirement. Aerial Conductor. An electric conductor carried from housetops, poles, or otherwise so as to be suspended in the air, as distinguished from an underground or submarine conductor. Affinity. The attraction of atoms and in some cases perhaps of molecules for each other by the force of chemical attraction. When the affinity is allowed to act or is carried out, a chemical change, as distinguished from a physical or mechanical change, ensues. Thus if sulphur and iron are each finely powdered and are mixed the change and mixture are mechanical. If slightly heated the sulphur will melt, which is a physical change. If heated to redness the iron will combine with the sulphur forming a new substance, ferric sulphide, of new properties, and especially characterized by unvarying and invariable ratios of sulphur to iron. Such change is a chemical one, is due to chemical affinity, is due to a combination of the atoms, and the product is a chemical compound. 13 STANDARD ELECTRICAL DICTIONARY. Agir Motor. The Anderson and Girdlestone motor. The term "agir" is made up from the first portions of each name. Agonic Line. The locus of points on the earth's surface where the magnetic needle points to the true north; an imaginary line determined by connecting points on the earth's surface where the needle lies in the true geographical meridian. Such a line at present, starting from the north pole goes through the west of Hudson's Bay, leaves the east coast of America near Philadelphia, passes along the eastern West Indies, cuts off the eastern projection of Brazil and goes through the South Atlantic to the south pole. Thence it passes through the west of Australia, the Indian Ocean, Arabia, the Caspian sea, Russia and the White sea to the North Pole. It crosses the equator at 70° W. and 55° E. approximately. (See Magnetic Elements.) Synonym--Agone. [Transcriber's note: The file Earth_Declination_1590_1990.gif provided by the U.S. Geological Survey (http://www.usgs.gov) is an animation of the declination of the entire earth.] Air. Air is a dielectric whose specific inductive capacity at atmosphere pressure is taken as 1. It is practically of exactly the same composition in all places and hence can be taken as a standard. When dry it has high resistance, between that of caoutchouc and dry paper. Dampness increases its conductivity. It is a mixture of oxygen and nitrogen, with a little carbonic acid gas and other impurities. Its essential composition is: Oxygen: (by weight) 23.14 (by volume) 21 Nitrogen: 76.86 79 The specific inductive capacity varies for different pressures thus: Approximate vacuum (.001 mm., .0004 inch) 0.94 (Ayrton) " " ( 5 mm. , .2 inches ) 0.9985 (Ayrton) 0.99941 (Boltzman.) The specific gravity of air under standard conditions 15.5° C (60° F.) and 760 mm. barometric pressure (30 inches) is taken as unity as a standard for gases. [Transcriber's note: Argon accounts for 0.9340%. It was discovered in 1894, two years after this book.] Air-Blast. (a) In the Thomson-Houston dynamo an air-blast is used to blow away the arc-producing spark liable to form between the brushes and commutator. It is the invention of Prof. Elihu Thomson. The air is supplied by a positive action rotary blower connected to the main shaft, and driven thereby. The wearing of the commutator by destructive sparking is thus prevented. A drum H H is rotated, being mounted on the axis X of the dynamo. As it rotates the three vanes are thrown out against the irregular shaped periphery of the outer case T T. The arrow shows the direction of rotation. The air is thus sent out by the apertures a a. O is the oil-cup. (b) The air-blast has also been used by Prof. Thomson in experiments with high frequency currents of high potential. By directing a blast of air against a spark discharge between ball terminals of an alternating current, the nature of the current was changed and it became capable of producing most extraordinary effects by induction. 14 STANDARD ELECTRICAL DICTIONARY. Fig. 5. AIR BLOWER FOR THOMSON'S DYNAMO. Air Condenser. A static condenser whose dielectric is air. The capacity of an air condenser in farads is equal to A / ( 4.452E12 * t ) in which A is the area of one sheet or sum of the areas of one set of connected sheets in square inches and t is the thickness of the layer of air separating them. A convenient construction given by Ayrton consists in a pile of glass plates P separated by little bits of glass F of known thickness, three for each piece. Tin-foil T is pasted on both sides of each piece of glass and the two coatings are connected. The tin-foil on each second plate is smaller in area than that on the others. The plates are connected in two sets, each set comprising every second plate. For A in the formula the area of the set of smaller sheets of tin-foil is taken. By this construction it will be seen that the glass does not act as the dielectric, but only as a plane surface for attachment of the tin-foil. Posts E E keep all in position. One set of sheets connects with the binding post A, the other with B. The capacity of any condenser with a dielectric of specific inductive capacity i is given by the formula: ( i *A^1 ) / ( 4.452E12 * t1 ) The air condenser is used for determining the value of i for different dielectrics. Fig. 6. AIR CONDENSER. 15 STANDARD ELECTRICAL DICTIONARY. Air Gaps. In a dynamo or motor the space intervening between the poles of the field magnet and the armature. They should be of as small thickness, and of as extended area as possible. Their effect is to increase the magnetic reluctance of the circuit, thereby exacting the expenditure of more energy upon the field. They also, by crowding back the potential difference of the two limbs, increase the leakage of lines of force from limb to limb of the magnet. Air Line Wire. In telegraphy the portion of the line wire which is strung on poles and carried through the air. Air Pump, Heated. It has been proposed to heat portions of a mercurial air pump to secure more perfect vacua, or to hasten the action. Heating expands the air and thus produces the above effects. 16 STANDARD ELECTRICAL DICTIONARY. Air Pump, Mercurial. An air pump operated by mercury. The mercury acts virtually as the piston, and the actuating force is the weight of the column of mercury, which must exceed thirty inches in height. There are many types. Mercurial air pumps are largely used for exhausting incandescent lamp chambers. (See Geissler Air Pump,--Sprengel Air Pump.) Air Pumps, Short Fall. A mercurial air pump in which the fall of mercury or the height of the active column is comparatively small. It is effected by using several columns, one acting after the other. A height of ten inches for each column suffices in some forms. Enough columns must be used in succession to make up an aggregate height exceeding 30 inches. Fig. 7. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. Fig. 8. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. Alarm, Burglar. A system of circuits with alarm bell extending over a house or apartments designed to give notice of the opening of a window or door. As adjuncts to the system the treads of the stairs are sometimes arranged to ring the bell, by completing a circuit when trod on. Door mats are also arranged to close circuits in like manner. 17 STANDARD ELECTRICAL DICTIONARY. For doors and windows switches are provided which are open as long as the door or window is closed, but which, on being released by opening the door or windows, automatically close the circuit. The circuit includes an alarm bell and battery, and the latter begins to ring and continues until stopped, either by the closing of the door or by a switch being turned. The connections are sometimes so contrived that the reclosing of the door or window will not stop the bell from ringing. The cuts show various switches for attachment to doors and windows. It will be seen that they normally keep the circuit closed, and that it is only open when pressure, as from a closed door, is brought upon them. In the case of a door a usual place for them is upon the jamb on the hinge side, where they are set into the wood, with the striking pin projecting, so that as the door is closed the pin is pressed in, thus breaking the circuit. Sometimes the connections are arranged so as to switch on the electric lights if the house is entered. Special annunciators showing where the house has been entered are a part of the system. A clock which turns the alarm on and off at predetermined hours is also sometimes used. The circuits may be carried to a central station or police station. One form of burglar alarm device is the Yale lock switch. This is a contact attached to a Yale lock which will be closed if the wrong key is used, completing a circuit and ringing a bell. Fig. 9. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. Alarm, Electric. An appliance for calling attention, generally by ringing a bell. It is used to notify of water-level in boilers or tanks, of entrance of a house, or of other things as desired. It is evident that any number of alarms could be contrived. 18 STANDARD ELECTRICAL DICTIONARY. Alarm, Fire and Heat. An alarm for giving notice of the existence of a conflagration. Such are sometimes operated by a compound bar thermostat (see Thermostat), which on a given elevation of temperature closes a circuit and rings an electric bell. Sometimes the expansion of a column of mercury when heated is used. This, by coming in contact with one or two platinum points, completes a circuit, and rings the bell. The identical apparatus may be used in living rooms, greenhouses. factories and elsewhere, to give an alarm when the temperature rises or falls beyond predetermined limits. Alarm, Overflow. An alarm to indicate an overflow of water has been suggested on the lines of a contact completed by water, or of the elements of a battery which would be made active by water. Thus two sheets of metal might be separated by bibulous paper charged with salt. If these sheets were terminals of a circuit including a bell and battery, when water reached them the circuit would be closed and the bell would ring. It was also proposed to use one copper and one zinc sheet so as to constitute a battery in itself, to be thrown into action by moisture. These contacts or inactive batteries could be distributed where water from an overflow would be most likely to reach them. Alarm, Water Level. An alarm operated by a change of water level in a tank or boiler. By a float a contact is made as it rises with the water. Another float may be arranged to fall and close a contact as the level falls. The closing of the contacts rings an electric bell to notify the attendant in charge. Alcohol, Electrical Rectification of. A current of electricity passed through impure alcohol between zinc electrodes is found to improve its quality. This it does by decomposing the water present. The nascent hydrogen combines with the aldehydes, converting them into alcohols while the oxygen combines with the zinc electrode. Alignment. The placing in or occupying of the same straight line. The bearings of a shaft in dynamos, engines, and other machinery have to be in accurate alignment. Allotropy. The power of existing in several modifications possessed by some substances, notably by chemical elements. Instances of the allotropic state are found in carbon which exists as charcoal, as graphite (plumbago or black lead), and as the diamond. All three are the same elemental substance, although differing in every physical and electrical property. 19 STANDARD ELECTRICAL DICTIONARY. Alloy. A mixture, produced almost universally by fusion, of two or more metals. Sometimes alloys seem to be chemical compounds, as shown by their having generally a melting point lower than the average of those of their constituents. An alloy of a metal with mercury is termed an amalgam. An important application in electricity is the use of fusible alloys for fire alarms or for safety fuses. German silver is also of importance for resistance coils, and palladium alloys are used for unmagnetizable watches. An alloy of wrought iron with manganese is almost unmagnetizable, and has been proposed for use in ship building to avoid errors of the compass. Alloys or what are practically such can be deposited by electrolysis in the electro- plater's bath. We give the composition of some alloys interesting to the electrician. Solder: Lead 1 part Tin 2 parts " " " 1 " " " " 2 " German Silver: Copper, 2 parts; Nickel, 1 part; Zinc, 1 part (used for resistances). Platinum, Silver Alloys: Platinum, 1 part; silver, 2 parts (used for resistances.) Palladium alloys for watch springs. (See Palladium.) Alphabet, Telegraphic. The combinations of sounds, of dots and dashes marked on paper, of right-hand and left-hand deflections of a needle, of bells of different notes, or of other symbols by which a fixed combination is expressed for each character of the alphabet, for numerals, and for punctuation. While the code is designed for telegraphic uses it can be used not only for the conveyance of signals and messages by the electrical telegraphs, but also by any semaphoric or visual system, as by flashes of light, movements of a flag or even of the arms of the person signalling. In the English and continental needle telegraphy in which the message is transmitted by the movements of an index normally vertical, but oscillating to one side or the other under the influence of the current, the latter being controlled by the transmitter of the message, the left hand swings of the needle are interpreted as dots, the right hand as dashes. This system enables one alphabet to be translated into the other, or virtually one alphabet answers for both Morse and needle transmitters. There are two principal telegraphic alphabets, the American Morse and the International codes. They are very similar, their essential distinction being that spaces are used in the American code, while they are excluded from the International code. In the American Morse system the message is now universally received by sound. (See Sounder--Sound Reading.) 20 STANDARD ELECTRICAL DICTIONARY. The two codes or telegraphic alphabets are given here. THE INTERNATIONAL ALPHABET. Parenthesis, - . - - . - Understand, ... - . I don't understand, ..-- ....--.. Wait, .-. . . Erase, ... ... ... Call signal, -.-.-.- End of message, .-.-.-. Cleared out all right, .-..-..-. A .- L .-.. W .-- B -... M -- X -..- C -.-. N -. Y -.-- D -.. O --- Z --.. E . P .--. F ..-. Q --.- Ch ---- G --. R .-. Ä .-.- H .... S ... Ö ---. I .. T - Ü ..-- J .--- U ..- É ..-.. K -.- V ...- Ñ --.-- NUMERALS 1 .---- 4 ....- 8 ---.. 2 ..--- 5 ..... 9 ----. 3 ...-- 6 -.... 0 ----- 7 --... [Transcriber's note: The original image of the dot/dash pattern is somewhat ambiguous. Since there may be differences from contemporary specifications, the original image is included.] [Image of page 20: THE INTERNATIONAL ALPHABET.] 21 STANDARD ELECTRICAL DICTIONARY. PUNCTUATION, ETC., Period (.) ... ... Comma (,) .-.-.- Query(?) ..--.. Exclamation (!) --..-- Apostrophe (') .----. Hyphen (-) -....- Fresh paragraph, .-.-.. Inverted commas, -..-. THE AMERICAN ALPHABET. A .- L ----(Continuous) W .-- B -... M -- X .-.. C ..s. N -. Y ..s.. D -.. O .s. Z …. E . P ..... F .-. Q ..-. Ch ---- G --. R .s.. Ä .-.- H .... S ... Ö ---. I .. T - Ü ..-- J - . - . U ..- É ..-.. K -.- V ...- Ñ --.-- NUMERALS 1 .--. 4 ....- 8 -.... 2 ..-.. 5 --- 9 -..- 3 ...-. 6 ... ... 0 -----(Continuous) 7 --.. [Transcriber's Note: The "s" in the American Code indicates a "space". I leave the following to the reader's imagination. See the original image.] Comma (,) Semicolon (;) Colon (:) Colon Dash (:~) Period (.) Interrogation (?) Exclamation (!) Dash (-) Hyphen (-) Pound Sterling (£) Shilling Mark ( ) [Image of page 21: THE AMERICAN ALPHABET.] 22 STANDARD ELECTRICAL DICTIONARY. [Transcriber's Note: I leave these to the reader's imagination. See the following original image.] Dollars ($) Decimal Point (.) Cents (c) Paragraph () Pence (d.) Fractional Mark (--) Capitalized Letter Italics or Underline Colon followed by Quotation :" Parenthesis ( ) Brackets [ ] Quotation Marks " " Quotation within a Quotation " ' ' " [Image of page 22: THE AMERICAN ALPHABET.] The principal differences in the two codes are the use of spaces in the American code, such being excluded from the International code. This affects the letters C, R, Y, & Z. The following diagram, due to Commandant Perian, enables the letter corresponding to an International code sign to be rapidly found with the exception of R. <- dot start dash -> / \ E T / \ / \ I A N M / \ / \ / \ / \ S U R W D K G O / \ / \ / \ / \ / \ / \ / \ / \ H V F U L A P J B X C Y Z Q Ô CH Fig. 10. Diagram for translating the Morse Alphabet. In order to find what letter corresponds to a given sign, starting from the top of the diagram, each line is traced down to a bifurcation, taking the right hand line of each bifurcation for a dash, and the left hand line for a dot, and stopping when the dots and dashes are used up. Thus, for example, the signal -.- - leads us to the letter d, the signal - - - - to the letter j and so on. 23 STANDARD ELECTRICAL DICTIONARY. Alternating. adj. Term descriptive of a current changing periodically in direction. (See Current, Alternating.) Synonyms--Oscillatory--periodic--undulatory--harmonic. Alternating Current Arc. The arc produced by the alternating current. It presents several peculiarities. With an insufficient number of alternations per second it goes out. As the carbons wear away equally it is adopted for such lamps as the Jablochkoff candle, (see Candle, Jablochkoff). As no crater is formed the light is disseminated equally both up and down. For this reason to get full downward illumination a reflector is recommended. Alternating Current System. A system of electric distribution employing the alternating current. For transmission in the open air or in conduits a high potential circuit is used, from 1,000 to 10,000 volts being maintained at the central station. Two leads unconnected at the end lead from the station. Where current is desired a converter or transformer (see Converter) is placed, whose primary is connected to the two leads bridging the interval between them. From the secondary the house leads are taken with an initial potential in some cases of 50 volts. The converters are thus all placed in parallel. By law or insurance rules the converters are generally kept outside of buildings. Where no secondary current is taken from the converters very little primary current passes them on account of their counter-electromotive force. As more secondary current is taken the primary increases and this accommodation of one to the other is one of the interesting and valuable features. Street lamps are sometimes connected in series. Each lamp in such case is in parallel with a small coil with iron core. While the lamp is intact little current passes through the coil. If the lamp is broken, then the converter impedes the current by its spurious resistance, q. v., just enough to represent and replace the resistance of the extinguished and broken lamp filament. (See Meter, Alternating Current; Motor, Alternating Current.) Alternation. The change in direction of a current. The number of such changes is expressed as number of alternations; thus a current may have a frequency of 500 or 20,000 alternations per second. [Transcriber's note: One alternation per second is now called one hertz.] Alternation, Complete. A double alternation; a change from one direction to the other and back again to the original phase. A symbol derived from its graphic representation by a sine curve is used to indicate it. The symbol is ~ 24 STANDARD ELECTRICAL DICTIONARY. Alternative Path. A second path for a current appearing as a disruptive discharge. Where two paths are offered the discharge, as it is of alternating or oscillatory type, selects the path of least self-induction. Thus a thick bar of copper, with no air gap, may be abandoned by the current in favor of a small iron wire with an air gap, but which has less self-induction. The lightning arresters, q. v., for the protection of telegraph offices are sometimes based on these principles. A path of very high resistance but of small self-induction is offered between the line and the earth. This the lightning discharge selects in preference to the instruments with their iron cores, as the latter are of very high self-induction. Alternator. A dynamo electric generator supplying an alternating current. (See Dynamo, Alternating Current.) Synonym--Alternating current generator or dynamo. Alternator, Constant Current. An alternating current dynamo supplying a current of unvarying virtual amperage. Alternators of this type are constructed with an armature of high self-induction. Sometimes fine winding contained in deep peripheral notches in the core-discs is employed to magnify the self-induction. Such generators are employed for series lighting, especially arc-lighting. Aluminum. A metal; one of the elements; symbol: Al. Atomic weight: 27.4. Equivalent: 9.13. Valency: 3. Specific gravity: 2.6. It is a conductor of electricity. Relative resistance annealed, (Silver = 1) 1.935 Specific resistance at 0ºC (32°F.) 2.912 microhms Resistance of a wire at 0ºC (32°F.) a) 1 foot long, weighing 1 grain, 0.1074 ohms. b) 1 foot long, 1/1000 inch thick, 17.53 " c) 1 meter long, weighing 1 gram, 0.0749 " d) 1 meter long, 1 millimeter thick 0.03710 " Resistance of a 1-inch cube at 0ºC (32°F.) 1.147 microhms Electro-chemical equivalent. .0958 (hydrogen == .0105) 25 STANDARD ELECTRICAL DICTIONARY. Amalgam. (a) A combination or alloy in which one of the constituents is mercury. Usually the term is applied to an alloy of a single metal with mercury. Some metals readily form amalgams; such metals are: Gold, zinc, silver, lead and others; some, such as platinum and iron, form amalgams only under exceptional circumstances. (b) The word is also applied to compositions for application to the cushions of frictional electric machine in which cases it is often a misnomer. True amalgams used for this purpose are made as follows: (a) Tin, 1 part; Zinc, 1 part; Mercury, 2 parts (Kienmayer). (b) Tin, 2 parts; Zinc, 3 parts. (c) Tin, 3 parts; Zinc, 5 parts; Mercury, 4 parts. (d) Zinc, 1 part: Mercury, 4 parts; Mercury, 9 parts. [sic] The tin, if such is used, (formula a, b and c) is first melted, the zinc is added in successive portions. The mercury, which must be heated, is slowly poured into the melted alloy after removal of the latter from the fire, and the mixture, while making, is constantly stirred. It is kept stirred or rubbed in a mortar until cold. Sometimes it is poured into water and kept in constant agitation until cold. It is thus obtained in a granular condition, and is pounded in a mortar until reduced to powder. It must be dried and kept in tightly stopped bottles and is applied to the cushions after they have been greased. It is to be noticed that it is said that alloy (d) requires no pulverization beyond constant rubbing in a mortar as it cools. Sometimes the amalgam is shaken about in a wooden tray with chalk while cooling. The action of amalgams is not very clearly understood. Some claim that there is a chemical action, others that they simply act as conductors, others that they are more highly negative to the glass than the leather of the cushions. Graphite or sulphide of tin (mosaic gold) are sometimes used to coat the cushions; it is these that are sometimes incorrectly called amalgams. Amalgamation. The application of mercury to a metal with which it forms an amalgam, or with which it amalgamates. Battery zincs are amalgamated in two ways. In the immersion method, the plate is dipped into an acid solution of mercuric chloride or nitrate. The latter is best. In the direct application method the plate is first wet all over with dilute acid and a little mercury is dropped upon it and is rubbed over the surface with a rag or, what is better, with a piece of galvanized iron. A very little mercury answers the purpose. The whole surface of the plate should be left as bright as silver. (See Action, Local.) Amber. Amber is a fossil resin, supposed to be a product of the extinct Pinites Succinifer and other coniferous trees. Most of it is gathered on the shores of the Baltic between Koenigsberg and Memel. It is also found in small pieces at Gay Head, Mass., and in New Jersey green sand. It is found among the prehistoric remains of the Swiss Lake dwellers. When rubbed with a cloth it becomes excited with negative electricity. The Greek word for it is electron, which gave the name electricity to the modern science. Thales of Miletus, 600 B. C., and Theophrastus, about 300 B. C., both mention its electric properties or power of attracting small objects when rubbed. 26 STANDARD ELECTRICAL DICTIONARY. Ammeter. The commercial name for an ampere-meter, an instrument designed to show by direct reading the number of amperes of current which are passing through a circuit. A great variety of ammeters have been invented, based on different principles. The definitions following this one give some idea of the lines of construction followed. Synonym--Ampere meter. Ammeter, Ayrton's. A direct reading instrument for measuring current intensity. A solenoid receives the current. In the axis of the solenoid an iron tube is suspended by a long spiral spring that passes down within it, and the upper end of which spring is fastened to the glass top of the instrument. The tube is provided with proper guides so as to maintain a vertical position, and is free to rotate. Its upper end carries an index. The whole operates as a magnifying device. A slight longitudinal displacement of the tube causes it to rotate through a considerable angle by the action of the spring. By properly proportioning the parts, the angle of displacement of the index is directly proportional to the current between 15º and 270º angular displacement. The same instrument is wound for use as a volt-meter. Its principal fault is its restricted range. Ammeter, Commutator. A commutator ammeter is one whose windings consist of separate strands, each of any desired number of turns, and provided with a commutating attachment for throwing them into series or into parallel as desired. The essential condition is that all the wires shall be of equal resistance and of equal number of turns. Such an instrument can be used for heavy or light currents. Two sets of graduations are marked on its scale if it is a calibrated instrument. (See Calibration.) Commutator volt-meters are constructed on the same principle. Ammeter, Cunynghame's. A modification of the Siemens' electro-dynamometer. (See Electro-dynamometer, Siemens'.) An electro-magnet with very massive core is excited by the current. As the core is of small reluctance the strength of the magnet is nearly proportional to the current strength. Between the poles of the magnet a soft iron armature or induced magnet is pivoted. It carries a pointer so adjusted that when the axis of the soft iron magnet is at an angle of about 30º with the line joining the poles of the electro-magnet the pointer will indicate zero. The soft iron armature is so massive that the magnetism induced in it is proportional to the strength of the electro-magnet. Hence the couple exerted by the electro-magnet on the pivoted armature will be proportional to the square of the current. The armature is retained in place by a spiral spring lying in line with its axis of rotation. The instrument is operated as a zero reading instrument. The current is passed through it. The needle is deflected; it is brought back to zero by turning a milled head which twists the spring. The current will be proportional to the square root of the angle of displacement of the milled head. A scale with index is provided, giving directly the square roots of the angle over which the pointer is moved. The same instrument is wound for use as a volt-meter. 27 STANDARD ELECTRICAL DICTIONARY. Ammeter, Eccentric Iron Disc. This ammeter comprises a cylindrical electro-magnet excited by the current to be measured. A disc of iron free to rotate is suspended on pivots below it. A piece is cut off the disc at one part of its periphery so as to give more metal to one side than to the other. In its zero position this portion of the disc swings towards the magnet. As the latter is more and more excited the other or more projecting portion of the disc turns towards it, being attracted like an armature, and moves against the force of gravity, the disc rotating. An index attached to the disc swings over the face of a graduated scale. The disc is so counterpoised that in its natural position the index points to zero. Ammeter, Electro-magnetic. An ammeter depending for its working upon the action of an electro-magnet, which is excited by the current to be measured. Ammeter, Gravity. An ammeter whose hand or index is drawn into the zero position by gravity, and whose displacement therefrom is produced by the action of the current to be measured. Fig. 11. GRAVITY SOLENOID AMMETER. Ammeter, Magnetic Vane. A fixed plate of soft iron is placed within a coil. Facing it is a second disc free to move or swing on an axis. When the field is excited the two repel each other because like polarity is induced in each, and the motion of the movable disc indicates the strength of the current. The same instrument is wound for high resistance and constitutes a Magnetic Vane Voltmeter. 28 STANDARD ELECTRICAL DICTIONARY. Ammeter, Magnifying Spring. A solenoid ammeter in which a spiral spring is used to convert the longitudinal motion of the armature or movable core into a rotary motion (see Ammeter, Ayrton's) and magnify the apparent range of motion. Ammeter, Permanent Magnet. An ammeter with a magnetic field produced by a permanent magnet. Ammeter, Solenoid. An ammeter in which the attraction, when a current is passing through it, exerted by a hollow coil of wire upon an iron bar or tube in line with its axis, is utilized to indicate the strength of current. The bar is drawn into the coil to different extents proportional to the attraction. As an example see Ammeter, Ayrton's, and cut of Gravity Ammeter. Ammeter, Spring. An ammeter in which the part moved by the current is controlled or brought to the zero position by a spring. Ammeter, Steel Yard. A solenoid ammeter in which the solenoid core is suspended vertically from the short end of a steel yard fitted with a sliding weight. The current passes through the solenoid coil and attracts or draws downwards the coil. A sliding weight is moved in and out on the long steel-yard arm which is graduated for amperes. In use the weight is slid out until the arm is in equipose; the divisions give the amperes. Fig. 12. STEEL YARD AMMETER. 29 STANDARD ELECTRICAL DICTIONARY. Ammunition Hoist, Electric. An apparatus for use on ships for hoisting ammunition to the guns by an electric elevator. The characteristic feature of it is that a constant motion of the switch or handle is required to keep it in action. If the operator is shot so as to be incapacitated from taking charge of the switch, the hoist stops until another is assigned to it. Amperage. Current intensity expressed in amperes, as an amperage of ten amperes. Ampere. The practical unit of electric current strength. It is the measure of the current produced by an electro-motive force of one volt through a resistance of one ohm. In electric quantity it is the rate of one coulomb per second. It is one-tenth the absolute C. G. S. unit of current strength. Its best analogy is derived from water. Assuming the electric current to be represented by a current of water, the pressure, head, or descent producing such current would be the electro-motive force. The current might be measured in gallons (or other unit) passed per second. In the analogy these gallons would be coulombs. But it might be measured by reference to a standard stream, as for instance, the stream which would pass through a hole an inch square under a given head, say six inches of water. This unit is the miner's inch, and is the exact analogy of the ampere. A current of water may flow at the rate of so many miner's inches, just as a current of electricity may flow at the rate of so many amperes. In neither case it will be noted is there any reference to time. "An ampere per second" is a redundant expression, and means no more than "an ampere"; an "ampere-second," on the other hand, is a coulomb. The number of coulombs passed per second gives the amperes of current. For value of ampere, see Coulomb. [Transcriber's note: The SI definition of an ampere: A current in two straight parallel conductors of infinite length and negligible cross-section, 1 metre apart in vacuum, would produce a force equal to 2E-7 newton per metre of length.] Fig. 13. THE MINER'S INCH AS AN ANALOGY FOR THE AMPERE. 30 STANDARD ELECTRICAL DICTIONARY. Ampere, Arc. A conductor bent into the arc of a circle, and employed in measuring the electric current by the electric balance. Ampere-currents. The currents assumed to be the cause of magnetism. (See Magnetism, Ampere's Theory of.) Ampere-feet. The product of amperes of current by the length, in feet, of a conductor passing such current. It may be in empiric calculations of dynamo or motor construction, but is little used. One ampere-foot is a current of one ampere passing through one foot length of a conductor, or one-tenth ampere through ten feet, and so on. Ampere-hour. The quantity of electricity passed by a current of one ampere in one hour. It is used by electric power and lighting companies as the unit of energy supplied by them, because they maintain a constant potential difference in their leads, so that only the amperes and hours need measuring or recording to give the energy, viz. : volt-ampere-hours. The same unit is applied to batteries to indicate their potential energy, because they also are assumed to be of constant voltage or electro-motive force. Ampere-meters. The product of amperes of current by the length, in meters, of a conductor carrying such current. One ampere-meter is a current of one ampere passing through one meter of a conductor. The term must not be confused with the identically spelled Ampere-meter, a synonym for Ammeter. Ampere-minute. The quantity of electricity passed by a current of one ampere in one minute; sixty coulombs. Ampere Ring. A conductor forming a ring or circle used in electric balances for measuring currents. (See Balance, Ampere.) Ampere-second. The quantity of electricity passed by a current of one ampere in one second; the coulomb, q. v. Amperes, Lost. In a shunt or compound-wound dynamo, part of the total amperes of current produced in the armature coils go through the shunt, and hence, do not appear in the outer circuit. S. P. Thompson has proposed the term "lost amperes" for this portion of the current. Ampere's Memoria Technica. An expression of the effect of a current on a magnetic needle. If we imagine the observer in the line of the current and facing the magnetic needle, the current entering by his feet and leaving by his head, the north pole is deflected to his left. 31 STANDARD ELECTRICAL DICTIONARY. Ampere-turns. The amperes of current supplied to a magnet coil multiplied by the number of turns the current makes in the coil. If the coil is wound two or three in parallel, the virtual turns by which the amperes are multiplied are one-half or one-third the actual turns of wire. Synonym--Ampere Windings. Ampere-turns, Primary. The ampere-turns in the primary coil of an induction coil or transformer. Ampere-turns, Secondary. The ampere-turns in the secondary coil of an induction coil or transformer. Amplitude of Waves. Waves are distinguished by length and amplitude. The latter, in the case of transverse waves, such as those of water and of the ether, correspond with and measure the height from lowest to highest point, or from valley to summit of the waves in question. In the case of longitudinal waves, such as those of the air, due to sounding bodies, the ratio of degree of rarefaction to degree of condensation existing in the system is the amplitude. The latter can be graphically represented by a sinuous line, such as would represent the section of a transverse wave. Ether waves are produced by heated bodies and by electro-magnetic impulses, as in the discharge of the Leyden jar. The amplitude of a wave, other things being equal, is the measure of its intensity. Thus, the louder a sound the greater is the amplitude of the system of waves to which it is due. The same applies to ether waves, whether they are perceived in the electro-magnetic, light, or heat-giving modification. As the amplitude of ether waves cannot be accurately known, amplitude is a relative term and is not stated generally in any absolute unit. Analogous Pole. One of the elements of a pyro-electric crystalline substance, such as tourmaline. When heated, such bodies acquire electrical properties. If of such crystalline form that they are differently modified at the ends of their crystalline axis, by hemihedral modifications, the ends may be differently affected. One end may show positive electricity when the temperature is rising, and negative when falling. Such end is then called the analogous pole. The opposite end presents, in such cases, the opposite phenomena; becoming negative when the temperature is rising, and becoming positive when it is falling; such end is called the antilogous pole. Analysis. The determination of the elements of a case. It may be chemical, and consist in finding what a substance consists of; it may be mathematical, and consist in determining the unknown quantities in a problem; or it may belong to other branches of science. The term has a very extended application. Where the constituents are only determined in kind it is called qualitative analysis; where their quantity or percentage is ascertained it is called quantitative analysis. 32 STANDARD ELECTRICAL DICTIONARY. Analysis, Electric. Chemical analysis by electrolytic methods. (See Electrolytic Analysis.) Analyzer, Electric. An apparatus used in investigations on electric ether waves. It consists of a series of parallel metallic wires. When the electric waves have been polarized, the analyzer will only permit them to go through it intact, when the plane of vibration of the waves is parallel to its wires. Anelectrics. (a) Bodies which do not become electrified by friction; a term introduced by Gilbert, now little used, as all bodies develop electricity under proper conditions by contact action; the reverse of idioelectrtics. (b) Also a conductor of electricity, the reverse of a dielectric, q. v. (See Conductor.) It will be seen that Gilbert's anelectrics were, after all, the same as the modern anelectrics, i.e., conductors. Anelectrotonus. A term used in medical electricity or electro-therapeutics to indicate the deceased functional activity induced in a nerve by the proximity of the anode of an active electric circuit completed through the nerve. The converse of Kathelectrotonus. Angle of Declination. The angle of error of the magnetic needle or compass, measuring the extent of its deviation from the meridian in any locality. It is the angle between the plane of the magnetic axis of a magnetic needle free to take its natural position, and the geographical meridian, the needle being counterpoised if necessary, so as to hold an absolutely horizontal position. The deviation is expressed as being east or west, referring always to the north pole. (See Magnetic Elements.) Synonym--Variation of the Compass. [Transcriber's note: See Agonic Line.] Angle of the Polar Span. In a dynamo or motor the angle subtended by the portion of a pole piece facing the armature, such angle being referred to the centre of the cross-section of the armature as its centre. STANDARD ELECTRICAL DICTIONARY. 33 Angular Velocity. The velocity of a body moving in a circular path, measured with reference to the angle it passes over in one second multiplied by the radius and divided by the time. A unit angle is taken (57°.29578 = 57° 17' 44".8 nearly) such that it is subtended by a portion of the circumference equal in length to the radius. Hence, the circumference, which is 360°, is equal to 2*PI*unit angle, PI being equal to 3.1416--. "Unit angular velocity" is such as would in a circle of radius = 1 represent a path = 1, traversed in unit time = 1 second. If the radius is r and the angle passed over is theta, the distance is proportional to r*theta; if this distance is traversed in t seconds the angular velocity is theta / t. The angular velocity, if it is multiplied by r, theta expressing a distance, will give the linear velocity. The dimensions of angular velocity are an angle (= arc / radius) / a Time = (L/L)/T = (T^-1). The velocity expressed by the rate of an arc of a circle of unit radius, which arc subtends an angle of 57° 17' 44".8, such arc being traversed in unit time, is unit angular velocity. Animal Electricity. Electricity, notably of high tension, generated in the animal system, in the Torpedo, Gymnotus and Silurus. The shocks given by these fish are sometimes very severe. The gymnotus, or electric eel, was elaborately investigated by Faraday. It has the power of voluntarily effecting this discharge. There is undoubtedly some electricity in all animals. The contact of the spinal column of a recently killed frog with the lumbar muscles produces contraction, showing electric excitement. Currents can be obtained from nerve and muscle, or from muscle sides and muscle cut transversely, in each case one thing representing positive and the other negative elements of a couple. Angle of Inclination or Dip. The angle which the magnetic axis of a magnet, which magnet is free to move in the vertical plane of the magnetic meridian, makes with a horizontal line intersecting such axis. To observe it a special instrument, the dipping compass, inclination compass, dipping needle, or dipping circle, as it is called, is used. (See Elements, Magnetic, --Dipping Needle,--Compass, Inclination.) Angle of Lag. The angle expressing the displacement of the magnetic axis of the armature core of a dynamo in the direction of its rotation. (See Lag.) Lag is due to the motion of the armature core. Angle of Lead. The angle expressing the displacement in the direction of rotation of the armature of a dynamo which has to be given the brushes to compensate for the lag. (See Lag.) This is positive lead. In a motor the brushes are set the other way, giving a negative angle of lead or angle of negative lead. Anion. The electro-negative element or radical of a molecule, such as oxygen, chlorine or the radical sulphion. (See Ions.) It is the portion which goes to the anode, q.v., in electrolytic decomposition. 34 STANDARD ELECTRICAL DICTIONARY. Anisotropic. (adj.) Unequal in physical properties, as in conduction and specific inductive capacity, along various axes or directions. An anisotropic conductor is one whose conductivity varies according to the direction of the current, each axis of crystallization in a crystalline body marking a direction of different conductivity. An anisotropic medium is one varying in like manner with regard to its specific inductive capacity. In magnetism an anisotropic substance is one having different susceptibilities to magnetism in different directions. The term is applicable to other than electric or magnetic subjects. Synonym--AEolotropic. Annealing, Electric. Annealing by the heat produced by the passage of the electric current through the body to be annealed. The object is clamped or otherwise brought into a circuit, and a current strong enough to heat it to redness, or to the desired temperature is passed through it. Annunciator. An apparatus for announcing a call from any place to another, as from a living-room to an office in a hotel, or for announcing the entering of any given room or window in a building protected by a burglar alarm. A usual system comprises for each annunciator an electro-magnet. Its armature is normally held away from its poles by a spring, and when in that position a latch connected to the armature holds a little shutter. When by a push-button or other device a current is sent through a circuit which includes the electro-magnet the armature is attracted, this releases the latch and the shutter drops. In dropping it displays a number, letter or inscription which indicates the locality of the push-button or other circuit-closing device. Often annunciators are connected in circuit with a bell. Fig. 14. ANNUNCIATOR. 35 STANDARD ELECTRICAL DICTIONARY. Annunciator Clock. A clock operating an annunciator by making contact at determined times. Annunciator Drop. The little shutter which is dropped by some forms of annunciators, and whose fall discloses a number, character or inscription, indicating whence the call was sent. Fig. 15. DROP ANNUNCIATOR. Fig. 16. ANNUNCIATOR DETACHING MECHANISM. Annunciator, Gravity Drop. An annunciator whose operations release shutters which fall by gravity. Annunciator, Needle. A needle annunciator is one whose indications are given by the movements of needles, of which there is usually a separate one for each place of calling. Annunciator, Swinging or Pendulum. An annunciator which gives its indications by displacing from its vertical position a pendulum or vertically suspended arm. 36 STANDARD ELECTRICAL DICTIONARY. Anodal Diffusion. A term in electro-therapeutics; the introduction of a medicine into the animal system by using a sponge-anode saturated with the solution of the drug in question. On passing a current the desired result is secured by cataphoresis, q. v. Anode. The positive terminal in a broken metallic or true conducting circuit; the terminal connected to the carbon plate of a galvanic battery or to its equivalent in case of any other generator. In general practice it is restricted to the positive terminal in a decomposition or electrolytic cell, such as the nickel anode in a nickel-plating bath or the anode of platinum in a gas voltameter. It is the terminal out of or from which the current is supposed to flow through the decomposition cell. In electro-therapeutics the term is used simply to indicate the positive terminal. In an electrolytic cell the electro-negative substance or anion goes to the anode. Hence, it is the one dissolved, if either are attacked. The nickel, copper or silver anodes of the electroplater dissolve in use and keep up the strength of the bath. The platinum anode in a gas voltameter is unattacked because the anion cannot act upon it chemically. Anodic Closure Contraction. A physiological change in a living subject produced by the closing of the electric current; the muscular contraction which takes place beneath the anode applied to the surface of the body when the circuit is closed, the kathode being applied elsewhere; it is due, presumably, to direct action on the motor nerve. It is a term in electro-therapeutics. It is the converse of anodic opening contraction, q. v. An abbreviation A. C. C. is often used to designate it. Anodic Duration Contraction. A term in electro-therapeutics. On the opening or closing of an electric circuit, the anode of which is placed over a muscle, a contraction is observed (see Anodic Closure Contraction--Anodic Opening Contraction). The above term is used to designate the duration of such contraction. An abbreviation A. D. C. is often used to designate it. Anodic Opening Contraction. The converse of Anodic Closure Contraction, q. v.; it is the contraction of living muscle beneath or near the anode where the circuit, including such anode and the body in its course, is closed; a physiological phenomenon observed in electro-therapeutics to which branch of science the term belongs. An abbreviation A. O. C. is often used to designate it. Anodic Reactions. A term in electro-therapeutics; the diagnosis of disease by the actions of the tissue near the anode of a circuit. Anti-Induction Conductor. A conductor constructed to avoid induction effects in the conducting element. Many kinds have been made. A tubular metal shield or envelope which may be grounded will protect an enclosed conductor to some extent. Or the conductor may be a double wire twisted around itself, one branch being used for the regular and the other for the return circuit, thus constituting a closed metallic circuit. The inductive effects are due to interrupted or varying currents in neighboring wires and circuits. Many anti-induction conductors have been invented and patented. 37 STANDARD ELECTRICAL DICTIONARY. Anti-magnetic Shield. In general terms a hollow screen of soft iron designed to protect any mass of steel behind or enclosed by it from magnetization by any magnet near it, such as a dynamo field magnet. This it does by concentrating the lines of force within its own mass, so that the space within it or enclosed by it is comparatively free from lines of force. It is often applied to watches, and is virtually an iron case in which they are enclosed. Antimony. A metal, one of the elements, atomic weight, 122: equivalent, 40.6 and 24.4; valency, 3 and 5; specific gravity, 6.8. It is a conductor of electricity. Relative resistance, compressed (silver = 1), 23.60 Specific resistance, 35.50 microhms. Resistance of a wire, (a) 1 foot long, weighing 1 grain, 3.418 ohms. (b) 1 foot long, 1/1000 inch thick, 213.6 " (c) 1 meter long, weighing 1 gram, 2.384 " (d) 1 meter long. 1 millimeter thick, 0.4521 " Resistance of a 1-inch cube, 13.98 microhms. Approximate percentage resistance per degree C. (1.8º F. at 20º C. 88º F.) 0.389 per cent. Elcctro-chemical equivalent (hydrogen = .0105) .2560 (See Thermo-Electric Series.) Anvil. An intermittent contact, or "make and break" of the current is sometimes produced by directly pressing a key down upon a metallic surface, the two being terminals of the circuit. The surface or stud on which such pressure is produced is called the anvil. The ordinary telegraph key, which makes a contact by the pressure of the operator's fingers does it by making a contact between a contact piece upon the front end of the key and the anvil. In the induction coil the anvil is also found. Thus in the cut representing the end of an induction coil and its circuit breaker in which O and O' and P and P' represent the secondary circuit terminal connections A is the core of soft iron wires, h is the anvil; the hammer when resting upon it so as to be in contact closes the circuit. When the current coming from the primary to the post i, passes through the hammer and anvil h, and emerges by m, it magnetizes the core; this attracts the hammer, which is made of or is armed with a mass of iron. This breaks the circuit. The hammer falls at once on the anvil, again making the circuit, and the action is repeated with great rapidity. Hammer and anvil or key and anvil connections should be made of platinum. Fig. 17. INDUCTION COIL CIRCUIT BREAKER. 38 STANDARD ELECTRICAL DICTIONARY. A. O. C. Abbreviation for Anodic Opening Contraction, q. v. Aperiodic. adj. In an oscillating apparatus, or in the oscillating member of apparatus, the fact of having no reference to time of vibration; dead-beat. Synonym. Dead-beat. 39 STANDARD ELECTRICAL DICTIONARY. Fig. 18. ARAGO'S DISC. Arago's Disc. An apparatus consisting of a disc of copper mounted horizontally, or on a vertical spindle, and so arranged as to be susceptible of rapid rotation. Immediately over it, and best with a pane of glass intervening, a magnetic needle is mounted on a pivot directly over the axis of the disc. If the disc is rotated the lines of force of the magnet are cut by it, and consequently currents are produced in the copper. These currents act upon the needle and cause it to rotate, although quite disconnected. It is advisable for the needle to be strong and close to the disc, which should rotate rapidly. Arc v. To form a voltaic arc. Arc, Compound. A voltaic arc springing across between more than two electrodes. Arc, Metallic. The voltaic arc produced between terminals or electrodes of metal. The characteristics of such arc as contrasted with the more usual arc between carbon electrodes are its greater length for the same expenditure of energy, its flaming character and characteristic colors due to the metals employed. It is sometimes, for the latter reason, used in spectroscopic investigations. Arc Micrometer. A micrometer for measuring the distance between the electrodes of a voltaic arc. Arc, Simple. A voltaic arc produced, as usual, between only two electrodes. 40 STANDARD ELECTRICAL DICTIONARY. Arc, Voltaic. The voltaic arc is the arc between two carbon electrodes slightly separated, which is produced by a current of sufficient strength and involving sufficient potential difference. The pencils of carbon are made terminals in a circuit. They are first placed in contact and after the current is established they are separated a little. The current now seems to jump across the interval in what sometimes appears an arch of light. At the same time the carbon ends become incandescent. As regards the distance of separation with a strong current and high electro-motive force, the arc may be several inches long. The voltaic arc is the source of the most intense heat and brightest light producible by man. The light is due principally to the incandescence of the ends of the carbon pencils. These are differently affected. The positive carbon wears away and becomes roughly cupped or hollowed; the negative also wears away, but in some cases seems to have additions made to it by carbon from the positive pole. All this is best seen when the rods are slender compared to the length of the arc. It is undoubtedly the transferred carbon dust which has much to do with its formation. The conductivity of the intervening air is due partly, perhaps, to this, but undoubtedly in great measure to the intense heating to which it is subject. But the coefficient of resistance of the intervening air is so much higher than that of any other part of the circuit that an intense localization of resistance occurs with corresponding localization of heating effect. This is the cause of the intense light. Thus if the carbons are but 1/32 of an inch apart as in a commercial lamp the resistance may be 1.5 ohms. The poor thermal conductivity of the carbon favors the concentration of heat also. The apparent resistance is too great to be accounted for by the ohmic resistance of the interposed air. A kind of thermoelectric effect is produced. The positive carbon has a temperature of about 4,000° C. (7,232° F.), the negative from 3,000° C. (5,432° F.) to 3,500° C. (6,322° F.). This difference of temperature produces a counter-electro-motive force which acts to virtually increase the resistance of the arc. The carbon ends of an arc can be projected with the lantern. Globules are seen upon them due to melted silica from the arc of the carbon. Fig. 19. EXPERIMENTAL APPARATUS FOR PRODUCING THE VOLTAIC ARC. 41 STANDARD ELECTRICAL DICTIONARY. Areometer. An instrument for determining the specific gravity of a fluid. It consists of an elongated body ballasted so as to float vertically and provided with a mark or a scale. It floats deeper in a light than in a heavy liquid. If it carries but one mark weights are added until that mark is reached, when the weights required give the specific gravity. Or the scale may give the reading directly based upon the depth to which it sinks. Areometers are often made of glass, ballasted with shot or mercury enclosed in their bottom bulb as shown. They are used in regulating battery solutions, and in watching the charging and discharging of storage batteries. Fig. 20. AREOMETER Fig. 21. BEAD AREOMETER Areometer, Bead. A tube of glass containing beads of different specific gravities. It has apertures at top and bottom. When immersed in a liquid, the same fills it, and the specific gravity within certain limits, depending on the factors of the beads, is shown by the beads which float and those which sink. It is used for storage batteries and other purposes where acids and solutions have to be tested. Argyrometry. The method of ascertaining the weight and inferentially the thickness of an electroplater's deposit of silver. It is done by weighing the article before and after plating. Arm. The four members of a Wheatstone bridge, q. v., are termed its arms. Referring to the diagram of a bridge, P, Q, R, S, are the arms. Fig. 22. DIAGRAM OF WHEATSTONE'S BRIDGE. Armature. (a.) A mass or piece of iron or steel, or a collection of pieces of iron designed to be acted on by a magnet. While nickel or cobalt might be used, they rarely or never are except in experimental apparatus. The armature of a permanent horse shoe magnet is simply a little bar of soft iron. When the magnet is not in use it is kept in contact with the poles with the idea of retaining its magnetism. It is then said to be used as a keeper. A bar magnet does not generally have an armature. The armature is also used to exhibit the attraction of the magnet. Sometimes an armature is made of steel and is permanently magnetized. Such an armature, termed a polarized armature, is repelled when its like poles are opposed to like poles of the magnet and otherwise is attracted with force due to the sums of the magnetism. If the magnet is sufficiently powerful depolarization of the armature may ensue when like poles are opposed to like poles. Polarized armatures are used in various appliances, magneto generators, telegraphic instruments and others. (b) In a dynamo or Motor the mass of laminated iron or of wire which carries the coils of insulated wires which are caused to rotate in the field of force of the field magnets in order to establish and maintain potential difference with its accompanying current, or which rotates under the effects of a current in a motor. (See Dynamo Electric Generator.) The work of the armature core is twofold. It acts as a portion of the magnetic circuit, conducting the lines of force, and by virtue of its high permeability or multiplying power concentrating a number of the lines of force through its own substance. To enable it to act with efficiency in this direction it should be made of iron of the highest permeability, and should approach as closely as possible to the armature cores consistent with leaving space for the wire winding. It next acts as a support for the wires which are to be swept through the field of force. Thus it acts both to establish a strong field and then acts as a carrier for the wires which are to be cut by the wires in question. In connection with this subject the different definitions under Armature, Dynamo, Commutator, Induction and similar topics may be consulted. (c) See Armature of Influence Machine. (d) See Armature of Leyden Jar or Static Condenser. 42 STANDARD ELECTRICAL DICTIONARY. Armature, Bar. An armature in a dynamo or motor whose winding is made up of conductors in the form of bars, round, rectangular and of other sections. This type of armature conductor is objectionable as Foucault currents are produced in it. It is found best to laminate or subdivide low resistance armature windings. [Transcriber's Note: Foucault currents are also called eddy currents.] Armature, Bipolar. An armature in which two poles are induced by the field. A bipolar field magnet produces a bipolar armature. Armature Bore. The cylindrical space defined by the pole pieces of a dynamo or motor within which the armature rotates. Synonym--Armature Chamber. 43 STANDARD ELECTRICAL DICTIONARY. Armature, Closed Coil. An armature for a motor or dynamo, the ends of all of whose coils are united, so as to be in one closed circuit all the way around. Fig. 23. CLOSED COIL GRAMME RING ARMATURE. Armature Coil, or Coils. The insulated wire wound around the core of the armature of an electric current generator or motor. Armature Core. The central mass of iron on which the insulated wire, to be rotated in the field of an electric current generator or motor, is wound. (See Dynamo-electric Machine and Motor, Electric.) Armature, Cylinder. An armature of the Gramme ring type, but longer in the axial direction, so that its core resembles a long hollow cylinder, the wire being wound inside and outside as in the Gramme ring. (See Gramme Ring.) Armature, Disc. (a) An armature of a dynamo electric machine or motor in which the coils are wound so as to be flat and are carried on the face of a disc forming the core or part of the core of the armature. S. P. Thompson treats it as a modified drum armature extended radially, the outer periphery corresponding to the back end of the drum. The poles of the field are generally placed to face the side or sides of the disc. (b) Another type of disc armature has its wire wound on bobbins arranged around the periphery of a disc. In disc armatures there is often no iron core, their thinness enabling this to be dispensed with. 44 STANDARD ELECTRICAL DICTIONARY. Fig. 24. DISC ARMATURE OF FRITSCHE MACHINE. Fig. 25. PLAN OF WINDING PACINOTTI'S DISC ARMATURE. Armature, Discoidal Ring. In a dynamo an armature of the shape of a ring of considerable radial depth of section as compared to its axial depth. It is generally made of iron ribbon or thin band wound to the proper size. Synonym--Flat Ring Armature. 45 STANDARD ELECTRICAL DICTIONARY. Armature, Drum. An armature for a dynamo or motor, consisting of a cylinder of iron preferably made up of discs insulated from each other by thin shellacked paper, or simply by their oxidized surfaces, and wound with wire parallel to the axis where it lies on the cylindrical periphery and crossing the heads approximately parallel to the diameter. It operates practically on the same principle as a Gramme Ring Armature. (See Gramme Ring.) Synonym--Cylindrical Armature. Armature Factor. The number of conductors on an armature, counted or enumerated all around its external periphery. Armature, Hinged. An armature pivoted to the end of one of the legs of an electro-magnet so as to be free to swing and bring its other end down upon the other pole. Fig. 26. HINGED ARMATURES OF CLUB-FOOT ELECTRO MAGNETS. Armature, Hole. An armature whose core is perforated to secure cooling. Synonym--perforated Armature. Armature, Intensity. An armature wound for high electro-motive force. A term little used at the present time. Armature Interference. A limit to the ampere turns permissible on a given armature is found in the increase of cross magnetizing effect, q. v., the increased lead necessitated, and the growth of the demagnetizing power. All such perturbing effects are sometimes expressed as armature interference. 46 STANDARD ELECTRICAL DICTIONARY. Armature, Load of. The circumflux, q. v., of the armature, or the ampere turns of the same. The maximum load which can be carried by an armature without sparking is directly proportional to the radial depth of core and to the length of the gap, and inversely proportional to the breadth of the polar span. Armature, Multipolar. An armature in which a number of poles greater than two is determined by the field. A multipolar field is employed for its production. Armature, Neutral. An armature of a magnet or telegraph relay which is not polarized or magnetized. Synonym--Non-polarized Armature--Neutral Relay Armature. Armature of Influence Machine. Pieces of paper pasted on the stationary plate of an electric machine of the Holtz type. Armature of Leyden Jar or Static Condenser. The inner and outer tin-foil coatings of a Leyden jar or other condenser. Armature, Open Coil. An armature of a dynamo or motor on which the coils are not joined in one closed circuit, but have their ends or some of them separated, and connected each to its own commutator bar or each set to their own bar. Fig. 27. OPEN COIL RING ARMATURE. 47 STANDARD ELECTRICAL DICTIONARY. Armature, Pivoted. An armature for an electro-magnet mounted on a pivot, which is at right angles to the yoke or parallel with the legs of the magnet, so as to be free to rotate. When the magnet is excited the armature is drawn into line or approximately so with its base or yoke. The system is used in some telegraph apparatus. Armature Pockets. Spaces or recesses in armatures provided for the reception of the coils. Armature, Polarized. An armature made of steel or having a steel core to which permanent magnetism has been imparted. Such are used in some forms of magneto current generators, and in telegraphic instruments. (See Relay, Polarized.) Armature, Pole. An armature having coils wound on separate poles projecting radially all around the periphery of its central hub or disc, or projecting internally from a ring-like frame, their ends facing the field magnet. Synonym--Radial Armature. Armature, Quantity. An armature of a dynamo or motor wound for current of large quantity. The term is now but little used. Armature-Reactions. When an armature is running in an active dynamo a series of reactions is established, the more important of which are: I. A tendency to cross-magnetize the armature. II. A tendency to spark at the brushes. III. A tendency for the armature current to demagnetize on account of the lead which has to be given to the brushes. IV. Variations in the neutral points as more or less current is taken from the machine. V. Heating of armature, both core and conductors, and of pole pieces, which heating is due to Foucault currents. Armature, Revolving, Page's. An early form of motor. The field is produced by a permanent magnet. Above its poles is a soft iron armature wound with a coil of insulated wire. A two-part commutator with contact springs conveys the current to the coil. The whole is so arranged that the polarity of the armature, as induced by the coil, through which a current is passed, is reversed as its ends sweep by the poles of the magnet. Then it is repelled from the poles and swings through 180° to have its polarity reversed and to go through the next 180°, and so on. Thus it rotates at a very high rate of speed. In the cut showing the elevation A, B, is the armature; f, g, the springs or brushes; h, the commutator with its sections o, i. In the section of the commutator W, W, designate the springs or brushes, A, the vertical spindle carrying the armature and commutator, and S, S, the commutator sections. 48 STANDARD ELECTRICAL DICTIONARY. Fig. 28. PAGE'S REVOLVING ARMATURE. Fig. 29. SECTION OF COMMUTATOR OF PAGE'S REVOLVING ARMATURE. W, W, Brushes; A, Spindle; S, S, Armature Segments. Armature, Ring. An armature whose core is in the shape of a ring, as the Gramme Ring Armature. (See Figs. 23 & 27.) 49 STANDARD ELECTRICAL DICTIONARY. Armature, Rolling. (a) An armature for a permanent horseshoe magnet consisting of a straight cylinder of soft iron on which a heavy wheel is mounted. When the legs of the magnet are inclined downward and the bar is laid across them it rolls down to the poles, across their ends, and back up the under side. It is merely a magnetic toy or illustrative experiment. Synonym--Wheel Armature. (b) Another form consists of little bars of iron with brass discs attached to the ends. On placing two of these together and bringing the poles of a magnet near them, as shown, they become magnetized with like polarity by induction and repel each other, rolling away in opposite directions. Fig. 30. ROLLING OR WHEEL ARMATURE. Fig. 31. ROLLING ARMATURES. Armature, Shuttle. The original Siemens' armature, now discarded. The core was long and narrow, and its cross section was nearly of the section of an H. The grooves were wound full of wire, so that the whole formed almost a perfect cylinder, long and narrow comparatively. (See Winding Shuttle.) Synonym--Siemens' Old Armature--Girder Armature--H Armature. Fig. 32. SHUTTLE OR H ARMATURE. Armature, Spherical. An armature of a dynamo which is wound on a spherical core, so as to be almost a sphere. It is employed in the Thomson-Houston dynamo, being enclosed in a cavity nearly fitting it, formed by the pole pieces. Armature, Stranded Conductor. A substitute for bar-armatures in which stranded copper wire conductors are substituted for the solid bar conductors, to avoid Foucault currents. (See Armature, Bar.) 50 STANDARD ELECTRICAL DICTIONARY. Armature, Unipolar. An armature of a unipolar dynamo. (See Dynamo Unipolar.) Armor of Cable. The metal covering, often of heavy wire, surrounding a telegraph or electric cable subjected to severe usage, as in submarine cables. Synonym--Armature of Cable. Arm, Rocker. An arm extending from a rocker of a dynamo or motor, to which arm one of the brushes is attached. (See Rocker.) Ordinarily there are two arms, one for each brush. Articulate Speech. Speech involving the sounds of words. It is a definition which has acquired importance in the Bell telephone litigations, one contention, concerning the Bell telephone patent, holding that the patentee did not intend his telephone to transmit articulations, but only sound and music. Astatic. adj. Having no magnetic directive tendency due to the earth's magnetism. Examples are given under Astatic Needle; Circuit, Astatic; and Galvanometer Astatic. Fig. 33. NOBILI'S PAIR. FIG. 34. VERTICAL PAIR ASTATIC COMBINATION. Astatic Needle. A combination of two magnetic needles so adjusted as to have as slight directive tendency as possible. Such a pair of needles when poised or suspended will hardly tend to turn more to one point of the compass than another. The combination is generally made up of two needles arranged one above the other, with their poles in opposite directions. This combination is usually called Nobili's pair. If of equal strength and with parallel magnetic axes of equal length they would be astatic. In practice this is very rarely the case. A resultant axis is generally to be found which may even be at right angles to the long axis of the magnets, causing them to point east and west. Such a compound needle requires very little force to turn it one way or the other. If one of the needles is placed within a coil of insulated wire a feeble current will act almost as strongly to deflect the system as if the other was absent, and the deflection will only be resisted by the slight directive tendency of the pair of needles. This is the basis of construction of the astatic galvanometer. Sometimes coils wound in opposite directions and connected in series, or one following the other, surround both needles, thus producing a still greater effect of deflection. Other astatic needles are shown in the cuts below. [Figures 33 to 35.] 51 STANDARD ELECTRICAL DICTIONARY. FIG. 35. SIMPLE ASTATIC NEEDLE. Asymptote. A line continuously approached by a curve, but which the curve, owing to its construction or nature of curvature, can never touch, be tangent to, or intersect. Atmosphere. (a) A term applied to the atmospheric pressure as a practical unit of pressure equal to 15 lbs. to the square inch as generally taken. It is really about 14.7 lbs. per square inch, or 1,033 grams per square centimeter. (b) Air, q. v. Atmosphere Residual. The atmosphere left in a vessel after exhaustion. The term may be applied to any gas. In an incandescent lamp after flashing the residual atmosphere consists of hydro-carbons. Atmospheric Electricity. The electricity of the atmosphere, rarely absent, but often changing in amount and sign. Benjamin Franklin, in a memoir published in 1749, indicated the method of drawing electricity from the clouds by pointed conductors. In June, 1752, he flew a kite and by its moistened cord drew an electric spark from the clouds, confirming his hypothesis that lightning was identical with the disruptive discharge of electricity. To observe electricity in fine weather a gold-leaf or other electroscope may be connected to the end of a long pointed insulated conductor. The electricity during thunderstorms can be shown by a similar arrangement, or burning alcohol or tinder gives an ascending current of warm air that acts as a conductor. Quite elaborate apparatus for observing and recording it have been devised. Atmospheric electricity is usually positive, but occasionally negative. When the sky is cloudless it is always positive, increasing with the elevation and isolation of the place. In houses, streets, and under trees no positive electricity can be found. In the Isle of Arran, Scotland, a rise of 24 to 48 volts per foot of increase in elevation was found by Sir William Thomson. At sunrise the electrification of the air is feeble, it increases towards noon and decreases again to reach a second maximum a few hours after sunset. It increases with the barometric pressure generally. In cloudy weather it is sometimes negative and the sign often changes several times in the same day. In a thunderstorm the changes in sign and potential are very rapid. The cause of atmospheric electricity is far from clear. Tait attributes it to a contact effect between air and water vapor, Solmeke to friction of water vesicles against ice particles in the upper atmosphere, he first showing that the two may coexist. The cause of the enormous increase of potential producing lightning is attributed to the decreased capacity due to the change of water from cloud vesicles to drops, thus diminishing the electrostatic capacity of the water in question. (See Lightning.) 52 STANDARD ELECTRICAL DICTIONARY. Atom. The ultimate particle or division of an elementary substance; the smallest part that can exist in combination, and one which cannot exist alone. An elementary substance is composed of molecules just as truly as a compound one, but the atoms in the molecule of an elementary substance are all precisely alike. Hence atoms are the units of chemistry, they have to do with combinations, but the physical unit, the smallest particle of matter that can have an independent existence, is the molecule. The two are often confounded, especially by writers of a few years ago, so that by "atom" the molecule is often meant. There is nothing to be said of their size or mass. All such calculations refer to the molecule, q. v., often spoken of and called the atom. [Transcriber's note: Yet to be discovered: electron--1897 (5 years), proton--1920 (28 years), neutron--1932 (30 years), quark--1961 (69 years).] Atomic Attraction. The attraction of atoms for each other, in virtue of which they combine into molecules; chemical affinity, q. v., treats principally of this, although molecular attraction also plays a part in it. Atomic Heat. The product of the atomic weight of a substance by its specific heat. This product is approximately the same, 6.4; this approximation is so close that it is of use in determining the valency and atomic weights of substances. The atomic weight of a substance therefore represents the approximate number of gram-calories required to raise one gram-atom, q. v., of such substance through 1° C. (1.8° F.) Atomicity. The quantivalence or valency of the atoms; the number of combination bonds, or bonds of affinity, possessed by the atoms of any substance. Thus two atoms of hydrogen combine with one atom of oxygen, and three of oxygen with one of sulphur, forming saturated compounds. Therefore, taking hydrogen as of single atomicity or a monad, oxygen is of double atomicity or a dyad, and sulphur is of six-fold atomicity, or a hexad. The elements are thus classified into seven orders of atomicities, thus: 1, Monads or Univalent elements, Hydrogen, etc. 2, Dyads or Bivalent " Oxygen, etc. 3, Triads or Trivalent " Nitrogen, etc. 4, Tetrads or Quadrivalent " Lead, etc. 5, Pentads or Quinquivalent " Phosphorous, etc. 6, Hexads or Sexivalent " Chromium, etc. 7, Heptads or Septivalent " Chromium, etc. The same element often possesses several atomicities. Barium is generally a dyad, sometimes a tetrad; nitrogen acts as a monad, dyad, triad, tetrad and pentad. The familiar electrolysis of water, giving two volumes of hydrogen to one of oxygen, is one of the illustrations of the theory indicating that two atoms of hydrogen are combined with one of oxygen. 53 STANDARD ELECTRICAL DICTIONARY. Atomic Weight. The number expressing the relative weight of the atom of any substance, that of hydrogen being generally taken as unity. This is the universal system, although any other element might be taken as the basis of the system. The whole theory of atomic weights is based on the indivisibility of the atom and on the theory of atomicity, q. v. (See Equivalents.) [Transcriber's note: The standard is now the isotope carbon-12 as exactly 12.] Attraction. The tendency to approach and adhere or cohere, shown by all forms of matter. It includes gravitation, cohesion, adhesion, chemical affinity and other forms, and is opposed by repulsion, and is sometimes overcome by it, although it may be assumed to be always present. See the different kinds of attractions under their titles: Atomic Attraction, Electro-magnetic Attraction and Repulsion, Electro Static Attraction and Repulsion, Electro-dynamic Attraction and Repulsion; Magnetic Attraction and Repulsion; Molar Attraction. Audiometer. An apparatus for obtaining a balance of induction from two coils acting upon a third. The third is placed between the other two and is free to move towards either. A scale is provided to show the extent of its movement. A varying or interrupted current being passed through the two outer coils, the preponderating current will produce the most induction if the central coil is equidistant. It can always be moved to such a point that there will be no inductive effect, one counteracting the other. Thus its position measures the relative induction. A telephone is in circuit with the intermediate coil and is used to determine when its position is such that no current is induced in it. It is sometimes used as a direct test of hearing. (See Hughes' Induction Balance.) Synonym--Acoutemeter. Aura, Electrical. The blast of air produced at highly electrified points. Aurora. A luminous display seen in the northern heavens in the northern hemisphere, where it is the Aurora Borealis, and seen in the southern heavens in the southern hemisphere, where it is called Aurora Australis, or indifferently for either, the Aurora Polaris. It takes the form of pale luminous bands, rays and curtains varying in color. Near the poles they are very numerous. A French commission observed 150 auroras in 200 days. Their height is variously estimated at from 90 to 460 miles; they are most frequent at the equinoxes and least so at the solstices. There is a secular variation also, they attain a maximum of occurrence every 11 years together with sun spots, with a minimum 5 or 6 years after the maximum. There is also a period of 60 years, coincident with disturbances in the earth's magnetism. Various attempts have been made to account for them. They have a constant direction of arc with reference to the magnetic meridian (q. v.) and act upon the magnetic needle; in high latitudes they affect telegraph circuits violently. There is a strong probability that they represent electric currents or discharges. De la Rive considers them due to electric discharges between the earth and atmosphere, which electricities are separated by the action of the sun in equatorial regions. According to Balfour Stewart, auroras and earth currents.(q. v.) may be regarded as secondary currents due to small but rapid changes in the earth's magnetism. The subject is very obscure. Stewart treats the earth as representing the magnetic core of an induction coil, the lower air is the dielectric, and the upper rarefied and therefore conducting atmosphere is the secondary coil. This makes the aurora a phenomenon of induced currents. Then the sun may be regarded as the instigator of the primary changes in the earth's lines of force representing the primary of an induction coil. [Transcriber's note: Solar wind, streams of electrons and protons, interacting with the earth's magnetic field causes aurora. Neither electrons (1897) nor protons (1920) were known in 1892. The Soviet satellite Luna first measured the solar wind in 1959. Even today increased understanding of solar and auroral phenomenon continues.] 54 STANDARD ELECTRICAL DICTIONARY. Austral Pole. The north pole of the magnet is thus called sometimes in France; the austral pole of a magnet is the one which points towards the north polar regions As unlike magnetic poles attract each other, it is but rational to call the north-seeking pole of the magnet the south or Austral Pole. In the same nomenclature the south pole of a magnet, or the south-seeking pole, is called the Boreal Pole. A. W. G. Abbreviation for American Wire Gauge, q. v. Axis, Electric. The electric axis of a pyroelectric crystal, such as a tourmaline crystal; the line connecting the points of greatest pyroelectric excitability. Axis of Abscissa. In a system of rectilinear, or right angle co-ordinates, the horizontal axis. (See Co-ordinates.) Synonym--Axis of X. Axis of Ordinates. In a system of rectilinear right angle co-ordinates, the vertical axis. (See Co-ordinates.) Synonym--Axis of Y. Azimuth. The angle between the plane of the meridian and the plane of an azimuth circle, q. v. Azimuth Circle. A great circle, whose plane passes through the zenith or point of the heavens directly overhead; any great circle in whose plane the vertical at the point of observation is included. Each celestial body has or determines an azimuth circle. 55 STANDARD ELECTRICAL DICTIONARY. B. (a) Abbreviation for Baumé, a hydrometer scale. (See Baumé.) Thus 10º B. means "ten degrees Baumé." (b) Symbol for the coefficient of induced magnetization, or the number of lines per square centimeter induced in a magnetic circuit or in any specified part of it. B. A. Abbreviation for British Association. It is prefixed to standards fixed by the committee of the British Association for the Advancement of Science. Thus the B. A. ohm means the British Association ohm, a measure of resistance which is equal to the resistance of a column of mercury 104.9 centimeters long and one square millimeter area of cross-section. (See Ohm.) Back Induction. A demagnetizing force produced in a dynamo armature when a lead is given the brushes. The windings by such setting of the brushes are virtually divided into two sets, one a direct magnetizing set, the other a cross magnetizing set. The latter have a component due to the obliqueness of the neutral line, which component is demagnetizing in its action. Back Shock or Stroke of Lightning. A lightning stroke received after the main discharge of the lightning, and caused by a charge induced in neighboring surfaces by the main discharge. The discharge affects the evenness of distribution of surrounding surfaces so that a species of secondary discharge is required to make even the distribution, or to supply charge where needed to bind an opposite one. The effects are much lese severe as a rule than those of the main charge, although the back stroke has caused death. The back stroke is sometimes felt a considerable distance from the place of the original lightning stroke. Synonym--Return Stroke. Back Stroke. (a) In telegraphy the return stroke of the lever in a telegraph sounder, striking the end of the regulating screw with a sound distinct from that which it produces on the forward stroke as it approaches the magnet poles. It is an important factor in receiving by ear or sound reading. (b) See Back Shock or Stroke of Lightning. Balance. (a) Wheatstone's Bridge, q. v., is sometimes termed the Electric Balance. (b) A suspension or torsion balance is one which includes a filament or pair of filaments to whose lower end or ends are attached a horizontal indicator often called a needle, or a magnetic needle. (See Torsion Balance.) (c) See Induction Balance, Hughes'. (d) For Thermic Balance, see Bolometer. (e) See Balance, Ampere. 56 STANDARD ELECTRICAL DICTIONARY. Balance, Ampere. A class of electrical measuring instruments due to Sir William Thomson may be grouped under this head. The instrument is a true balance or scales such as used for weighing. It is supported by a torsional wire support in place of knife edges. At each end it carries a circle of wire through which the current to be tested is passed. The torsional wire support enables the current to be carried to these wire rings. Above and below each of these rings are two similar rings, also connected so as to receive the current. They are so connected that the current shall go through them in opposite senses. When a current passes, therefore, one of these rings repels and one attracts the balanced ring. The extent of this action measures the intensity of the current. A sliding weight moving along a graduated scale on the balance is used to bring the balance beam into equilibrium when the current is passing. The degree of displacement of this weight gives the strength of the current in amperes. These balances are made for different currents. Thus there is a centi-ampere balance, deka-ampere balance and others, as well as an ampere balance. Balata. A gum used as an insulating material. It is the inspissated juice of a sapotaceous tree, the bullet tree, Mimusops globosa, of tropical America, from the Antilles to Guiana. It is intermediate in character between caoutchouc and gutta percha. It is superior to gutta percha in some respects, being very slightly acted on by light. Synonym--Chicle. B. & S.. W. G. Abbreviation for Brown & Sharpe Wire Gauge; the regular American Wire Gauge. (See Wire Gauge, American.) Barad. An absolute or fundamental unit of pressure, equal to one dyne per square centimeter. Barometer. An apparatus for measuring the pressure exerted by the atmosphere. It consists, in the mercurial form, of a glass tube, over 31 inches long, closed at one end, filled with mercury and inverted, with its open end immersed in a cistern of mercury. The column falls to a height proportional to the pressure of the atmosphere from 30 to 31 inches at the sea level. The "standard barometer" is a height of the mercury or of the "barometric column" of 30 inches or 760 centimeters, measured from the surface of the mercury in the cistern. The column of mercury is termed the barometric column. Above it in the tube is the Torricellian vacuum. [Transcriber's note: More accurately, 29.92 inches of mercury or 14.696 PSI.] Bars of Commutators. The metal segments of a commutator of a dynamo or motor. They are made of bars of copper, brass or bronze insulated from one another. (See Commutator.) Synonyms--Segments, Commutator Segments, Commutator Bars. 57 STANDARD ELECTRICAL DICTIONARY. Bath. (a) In electro-plating the solution used for depositing metal as contained in a vat or tank; as a silver, copper, or nickel bath used for plating articles with silver, copper, or nickel respectively. (b) In electro-therapeutics a bath with suitable arrangements, electrodes and connections for treating patients with electricity. It is termed an electric bath or electro-therapeutic bath. Bath, Bipolar Electric. In electro-therapeutics a bath in which the electrodes are both immersed in the water. The patient placed between them receives part of the discharge. The electrodes are large copper plates, termed shovel electrodes. Bath, Electric Shower. An electro-medical shower bath. The patient is placed on a metallic stove or support connected to one of the electric terminals. Water slightly alkaline is showered upon him. The other electrode is in connection with the water. The rain of drops and streamlets is the conductor of the current or discharge. Bath, Multipolar Electric. An electro-medical bath with a number of electrodes instead of two. Bath, Stripping. In electro-plating a solution used for dissolving and thus removing the plating from any object. The stripping bath is of the same general type as the plating bath for the same metal as the one to be dissolved. The object to be "stripped" is made the anode of a plating circuit, and as the current acts the old plating is attacked and dissolves, leaving the body of the article bare. It is simply the operation of plating reversed. The same term is applied to baths acting by simple solution. Stripping baths are described under the different metals as Silver Bath, Stripping--Gold Bath, Stripping. Bath, Unipolar Electric. An electro-medical bath, in which only one electrode connects with the water of the bath. The second electrode is supported above the bath. The patient touches this while in the water whenever electric action is desired. FIG. 36. THREE WIRE MOULDING OR BATTEN. FIG. 37. TWO WIRE MOULDING OR BATTEN. 58 STANDARD ELECTRICAL DICTIONARY. Batten. A strip of wood grooved longitudinally for holding wires in wiring apartments for electric light or power. In use they are fastened to the wall, grooves inward, or else grooves outward, with the wires lying in the grooves and covered with the covering strip. For two wire work each batten contains two grooves; for the three wire system it contains three grooves. Synonym--Moulding. Battery. A combination of parts or elements for the production of electrical action. The term is principally applied to voltaic batteries, but there are also magnetic batteries, batteries of Leyden jars, and other combinations, described in their places, which come under this category. [Transcriber's note: A group of similar items such as questions, machines, parts, guns, or electric cells.] Battery, Acetic Acid. A battery whose active solution or excitant is acetic acid or vinegar. This acid has been used by Pulvermacher in his medical battery, as being a substance found in every household in the form of vinegar. It is now but little used. Battery, Alum. A battery using as excitant a solution of alum. This battery has had some application for electric clocks, but only to a limited extent. Fig. 38. BALLOON OR FLASK BATTERY. Battery, Aluminum. A battery in which aluminum is the negative plate and aluminum sulphate the excitant. It is mounted like the gravity battery. Its electro-motive force is 0.2 volt. 59 STANDARD ELECTRICAL DICTIONARY. Battery, Bagration. A battery with zinc and carbon electrodes immersed in earth sprinkled with sal ammoniac (ammonium chloride). The copper is preferably first immersed in sal ammoniac solution and dried, until a green layer is formed on its surface. The battery is highly praised for its constancy by De la Rive, but may be regarded as obsolete. Battery, Balloon. A form of gravity battery into whose centre a globular flask, B, is inverted, which is filled before inversion with copper sulphate, of which 2 lbs. are used, and water, so as to remain full. This acts as a reservoir of copper sulphate, which it constantly supplies. The glass jar is closed with a perforated wooden cover. Battery, Banked. (a) A battery arranged to feed a number of separate circuits. (b) A battery connected in parallel or in multiple arc. Battery, Bichromate. A battery with amalgamated zinc and carbon plates, with an exciting fluid composed of sulphuric acid, water, and potassium bichromate. For formula of such solutions see Electropoion Fluid--Kookogey's Solution--Poggendorff's Solution--Trouvé's Solution--Delaurier's Solution, and others. (See Index.) Battery, Bunsen. A two fluid porous cell battery. The negative plate is carbon, the positive plate, amalgamated zinc. The depolarizer is nitric acid or electropoion fluid, q.v., in which the carbon is immersed. The last named depolarizer or some equivalent chromic acid depolarizing mixture is now universally used. The excitant is a dilute solution of sulphuric acid. Originally the carbon was made cylindrical in shape and surrounded the porous cups, in which the zinc was placed. This disposition is now generally reversed. The electro-motive force is 1.9 volts. The depolarizing solution is placed in the compartment with the carbon. The excitant surrounds the zinc. Fig. 39. BUNSEN'S BATTERY. 60 STANDARD ELECTRICAL DICTIONARY. Battery, Cadmium. A battery in which cadmium is the negative plate, sulphate of cadmium solution the excitant and depolarizer, and zinc the positive plate. Electro-motive force, .31 volt or about one third of a Daniell cell. It is mounted like a gravity battery. Battery, Callan. A modification of Grove's battery. Platinized lead is used for the negative plate, and as a depolarizer a mixture of 4 parts concentrated sulphuric acid, 2 parts of nitric acid, and 2 parts of a saturated solution of potassium nitrate. (See Battery, Grove's.) Battery, Camacho's. A battery with carbon negative and amalgamated zinc positive electrodes. The carbon is contained in a porous cup, packed with loose carbon. Electropoion or other fluid of that type serves as excitant and depolarizer, and is delivered as shown from cell to cell by syphons. Fig. 40. CAMACHO'S BATTERY. Battery, Carré's. A Daniell battery for whose porous cup a vessel or species of sack made of parchment paper is substituted. The battery has been used for electric light, and has been run for 200 successive hours, by replacing every 24 hours part of the zinc sulphate solution by water. 61 STANDARD ELECTRICAL DICTIONARY. Battery, Cautery. A battery used for heating a platinum wire or other conductor used for cauterization in electro-therapeutics. The term is descriptive, not generic. Battery, Chloric Acid. A battery of the Bunsen type in which an acidulated solution of potassium chlorate is used as depolarizer. Battery, Chloride of Lime. A battery in which bleaching powder is the excitant. The zinc electrode is immersed in a strong solution of salt, the carbon in a porous vessel is surrounded with fragments of carbon and is packed with chloride of lime (bleaching powder). There is no action on open circuit. It has to be hermetically sealed on account of the odor. Its electro-motive force is--initial, 1.65 volts; regular, 1.5 volts. Synonym--Niaudet's Battery. Battery, Chromic Acid. Properly a battery in which chromic acid is used as a depolarizer. It includes the bichromate battery. (See Battery, Bichromate.) Battery, Closed Circuit. A battery adapted by its construction to maintain a current on a closed circuit for a long time without sensible polarization. The term is merely one of degree, for any battery becomes exhausted sooner or later. As examples the Grove, Bunsen or Daniell batteries may be cited. 62 STANDARD ELECTRICAL DICTIONARY. Fig. 41. COLUMN BATTERY. Battery, Column. The original Volta's pile. It consists of a series of compound circular plates, the upper or lower half, A, copper; the other, Z, of zinc. Between each pair of plates some flannel or cloth, u, u, is laid, which is saturated with dilute acid. As shown in the cut, the parts are laid up in two piles, connected at the top with a bar, c, c, and with vessels of acidulated water, b, b, as electrodes. The great point in setting it up is to be sure that no acid runs from one disc of flannel to the next over the outside of the plates, as this would create a short circuit. The plates are best compound, being made up of a zinc and a copper plate soldered together. They may, however, be separate, and merely laid one on the other. In such case great care must be taken to admit no acid between them. Volta's pile is no longer used, except occasionally. Trouvé's blotting paper battery (see Battery, Trouvé's) is a relic of it, and the same is to be said for Zamboni's dry pile. It rapidly polarizes, the flannel retains but little acid, so that it is soon spent, and it is very troublesome to set up. Great care must be taken to have the cloth discs thoroughly saturated, and wrung out to avoid short circuiting by squeezing out of the acid. Battery, D'Arsonval's. A battery of the Bunsen type, differing therefrom in the solutions. As excitant in which the zinc electrode is immersed, the following solution is used: Water, 20 volumes; Sulphuric Acid (purified by shaking with a little olive or similar oil), 1 volume; hydrochloric acid, 1 volume. As polarizer in which the carbon is immersed the following is used: Nitric acid, 1 volume; hydrochloric acid, 1 volume; water acidulated with 1/20th sulphuric acid, 2 volumes. Battery, de la Rue. A battery with zinc positive and silver negative electrode; the depolarizer is silver chloride; the excitant common salt or ammonium chloride. The cut shows one of its forms of construction. The right hand portion of the cut, Fig. 42, shows the zinc perforated at C for the connection from the next silver plate. The next to it is the negative electrode of silver around which a mass of silver chloride is cast in cylindrical form. A is a parchment paper cylinder with two holes near its top, through which the silver wire of the negative electrode is threaded, as shown in B. A solution of 23 parts ammonium chloride in 1,000 parts of water is the approved excitant. Its electro-motive force is 1.03 volts. The jars are closed with paraffin. Fig. 42. DE LA RUE'S BATTERY. 63 STANDARD ELECTRICAL DICTIONARY. Battery, Dry. (a) A form of open circuit battery in which the solutions by a mass of zinc oxychloride, gypsum, or by a gelatinous mass such as gelatinous silica, or glue jelly, are made practically solid. Numbers of such have been patented, and have met with considerable success. (b) Zamboni's dry pile, q. v., is sometimes termed a dry battery. Battery, Element of. A term applied sometimes to a single plate, sometimes to the pair of plates, positive and negative, of the single couple. Battery, Faradic. A term applied, not very correctly however, to apparatus for producing medical faradic currents. It may be an induction coil with battery, or a magneto-generator worked by hand. Battery, Ferric Chloride. A battery of the Bunsen type, in which a solution of perchloride of iron (ferric chloride) is used for the depolarizing agent. A little bromine is added with advantage. The depolarizing agent recuperates on standing, by oxidation from the oxygen of the air. Battery, Fuller's. A battery of the Bunsen type. The zinc plate is short and conical, and rests in the porous jar into which some mercury is poured. An insulated copper wire connects with the zinc. A plate of carbon is in the outer jar. The solutions are used as in the Bunsen battery. Synonym--Mercury Bichromate Battery. Battery, Gas. (a) A battery whose action depends on the oxidation of hydrogen as its generating factor. It was invented by Grove. Plates of platinum are immersed in cups of dilute acid, arranged as if they were plates of zinc and carbon, in an ordinary battery. Each plate is surrounded by a glass tube sealed at the top. The plates are filled with acid to the tops. Through the top the connection is made. A current from another battery is then passed through it, decomposing the water and surrounding the upper part of one set of plates with an atmosphere of oxygen and of the other with hydrogen. Considerable quantities of these gasses are also occluded by the plates. On now connecting the terminals of the battery, it gives a current in the reverse direction of that of the charging current. This battery, which is experimental only, is interesting as being the first of the storage batteries. (b) Upward's Chlorine Battery and any battery of that type (see Battery, Upward's,) is sometimes termed a gas battery. 64 STANDARD ELECTRICAL DICTIONARY. Battery Gauge. A pocket or portable galvanometer for use in testing batteries and connections. Battery, Gravity. A battery of the Daniell type, in which the porous cup is suppressed and the separation of the fluids is secured by their difference in specific gravity. A great many forms have been devised, varying only in details. The copper plate, which is sometimes disc shaped, but in any case of inconsiderable height, rests at the bottom of the jar. Near the top the zinc plate, also flat or of slight depth, is supported. As exciting liquid a strong solution of copper sulphate lies at the bottom of the jar. This is overlaid by a solution of zinc sulphate, or sodium sulphate, which must be of considerably less specific gravity than that of the copper sulphate solution. In charging the jar one-tenth of a saturated solution of zinc sulphate mixed with water is sometimes used as the upper fluid. This may be first added so as to half fill the jar. The strong solution of copper sulphate may then be added with a syphon or syringe underneath the other so as to raise it up. From time to time copper sulphate in crystals are dropped into the jar. They sink to the bottom and maintain the copper sulphate solution in a state of saturation. Fig. 43. GRAVITY BATTERY OF THE TROUVÉ-CALLAUD TYPE. If the battery is left on open circuit the liquids diffuse, and metallic copper precipitates upon the zincs. This impairs its efficiency and creates local action. As long as the battery is kept at work on closed circuit work but little deposition, comparatively speaking, occurs. From time to time, in any case, the zinc plates are removed and scraped, so as to remove the copper which inevitably forms on their surface. Care must be taken that the zinc sulphate solution, which is constantly increasing in strength, does not get so strong as to become of as high specific gravity as the copper sulphate solution. From time to time some of the upper solution is therefore removed with a syphon or syringe and replaced with water. An areometer is useful in running this battery. 65 STANDARD ELECTRICAL DICTIONARY. Battery, Grenet. A plunge battery with zinc positive and carbon negative electrodes. Electropoion or other chromic acid or bichromate solution is used as depolarizer and excitant. The zinc plate alone is plunged into and withdrawn from the solution. Fig. 44. GRENET'S BATTERY. Fig. 45. GROVE'S BATTERY. Battery, Grove's. A two fluid galvanic battery. A porous cup has within it a riband of platinum, which is the negative plate; amalgamated zinc in the outer jar is the positive plate. Dilute sulphuric acid (10 per cent. solution) is placed in the outer jar, and strong nitric acid (40° B.) as a depolarizer in the porous cups. Its E. M. F. is 1.96 volts. It is objectionable, as it gives off corrosive nitrous fumes. These are produced by the oxidation of the nascent hydrogen by the nitric acid, by the following reaction: 3 H + H N O3 = 2 H2 O + N O. There are other reactions, one of which results in the formation of ammonia by the reduction of the nitric acid radical by the hydrogen. Ammonium can be detected in the spent liquids. 66 STANDARD ELECTRICAL DICTIONARY. Battery, Hydrochloric Acid. A battery in which hydrochloric acid is used as the excitant. Many attempts have been made to use this acid in batteries, but the volatile nature of the acid causes the production of so much odor with corrosive fumes that it has never come into use. Battery, Lead Chloride. A battery of the lead sulphate type in which lead chloride is the depolarizer. It has had no extended use. Battery, Lead Sulphate. A battery similar to Marié Davy's battery or the gravity battery, but using lead sulphate as depolarizer and excitant. Lead, copper or tin is the material of the negative plate. Becquerel used the lead sulphate as a solid cylindrical mass surrounding a lead rod 1/5 to 1/4 inch in diameter. One part of common salt may be mixed with 5 parts of the lead sulphate. The electro-motive force is about 0.5 volt. The resistance is very high. Battery, Leclanché. An open circuit battery with porous cup. In the outer jar is a zinc rod; a carbon plate is placed in the porous cup. The latter is packed with a mixture of clean powdered manganese binoxide as depolarizer, and graphite in equal volumes. A strong solution of ammonium chloride (sal ammoniac) is placed in the outer jar. It is only used on open circuit work. Its electromotive force is 1.48 volts, when not polarized. The reaction is supposed to be about the following: 2 N H4 Cl + 2 Mn O2 + Zn = Zn Cl2 + 2 N H3 + H2 0 + M2 O3 The battery rapidly weakens on open circuit, but quickly recuperates. There is another form of this battery, termed the agglomerate battery. (See Battery, Leclanché Agglomerate.) Fig. 46. LECLANCHÉ BATTERY. Battery, Leclanché Agglomerate. A form of the Leclanché in which the porous jar is suppressed. Cakes made of a mixture of carbon, 52 parts; manganese binoxide, 40 parts; gum lac, 5 parts; potassium bisulphate, 3 parts, compressed at 300 atmospheres, at a temperature of 100° C. (212° F.), are fastened by India rubber bands or otherwise against the carbon plate. These constitute the depolarizer. Various shapes are given the carbon and depolarizing agglomerates. Battery, Local. A battery supplying a local circuit (see Circuit. Local). The current is governed by the relay situated on the main line and operated by its current. Battery, Main. The battery used in operating the main line. It is usually applied to telegraphy. Its function is then to supply current for working relays, which in turn actuate the local circuits. Main and local circuits and batteries are also used in the automatic block system of railroad signalling. 67 STANDARD ELECTRICAL DICTIONARY. Battery, Marié Davy's. A two fluid porous cup battery with carbon negative plate, zinc positive plate, and mercury sulphate, a nearly insoluble salt, as depolarizer and excitant. Mercurous or mercuric sulphates have been used in it. Its electromotive force is 1.5 volts. The local action and waste, owing to the slight solubility of the mercury compounds, is very slight. If used on close circuit it becomes polarized. It is also subject under extreme circumstances to reversal of polarity, zinc becoming deposited upon the carbon, and there forming a positive electrode. In using the cells in series the level of liquid in all must be the same, otherwise the cell in which it is lowest will become polarized and exhausted. Modifications of this battery on the lines of the gravity battery have been constructed. Synonym--Sulphate of Mercury Battery. Battery, Maynooth's. A battery of the Bunsen type, with cast iron negative plate. The iron takes the passive form and is not attacked. Battery, Medical. A term applied very indiscriminately to medical current generators, and to medical induction coils, or to any source of electricity, static or current, for medical application. 68 STANDARD ELECTRICAL DICTIONARY. Battery, Meidinger's. A variety of Daniell cell of the gravity type. The plates are cylindrical. The zinc plate lies against the upper walls of the vessel. The copper plate of smaller diameter rests on the bottom. A large tube, with an aperture in its bottom, is supported in the centre and is charged with copper sulphate crystals. The cup is filled with a dilute solution of Epsom salts (magnesium sulphate) or with dilute sulphuric acid. Battery Mud. A deposit of mud-like character which forms in gravity batteries and which consists of metallic copper precipitated by the zinc. It indicates wasteful action. Battery, Multiple-connected. A battery connected in parallel, all the positive plates being connected to one electrode, and all the negative to another. Battery, Nitric Acid. A battery in which nitric acid is used as the excitant. Owing to its cost and volatility this acid has been but little used in batteries, other than as a depolarizer. In Grove's battery (see Battery, Grove's) it has been thus used. Battery of Dynamos. A number of dynamos may be arranged to supply the same circuit. They are then sometimes termed as above, a Dynamo Battery. They may be arranged in series or in parallel or otherwise combined. Battery of Leyden Jars. To produce the quantity effect of a single large Leyden jar with a number of small ones they are often connected in parallel and termed a battery. In such case the inner coatings are all connected by regular bar conductors, and the outside coatings are also all in connection. They are conveniently placed in a box or deep tray whose inner surface is lined with tinfoil, with an outside connection for grounding, etc. The cascade, q. v., arrangement is not so generally termed a battery. Battery, Open Circuit. A battery adapted for use in open circuit work. Its main requirement is that it shall not run down, or exhaust itself when left on open circuit. The Leclanché battery is very extensively used for this work. Its action is typical of that of most open circuit batteries. It is without any action on open circuit. It is very quickly exhausted on closed circuit, but recuperates or depolarizes quite soon when on open circuit. It is always in condition for a momentary connection, but useless for steady work. Battery, Oxide of Copper. A battery with zinc positive and iron negative electrodes. The excitant is a 30 or 40 per cent. solution of sodium or potassium hydrate (caustic soda or caustic potash). The depolarizer is copper oxide. In action the copper is gradually reduced to the metallic state. The iron element is often the containing vessel. The battery is practically inactive on open circuit. Its electro-motive force varies from .75 to .90 volt. To prevent the formation of sodium or potassium carbonate the cell should be closed, or else the liquid should be covered with mineral oil. Synonyms--Lalande & Chaperon Battery--Lalande-Edison Battery. 69 STANDARD ELECTRICAL DICTIONARY. Battery, Peroxide of Lead. A battery in which peroxide of lead (lead binoxide) is the depolarizer. It is a sort of predecessor of the present secondary battery. Battery, Platinized Carbon. A modification of Smee's battery, in which platinized carbon is used for the negative plates. Before polarization the E. M. F. is equal to that of Smee's battery. Polarization reduces its electro-motive force one-half. Battery, Plunge. A battery whose plates are mounted so as to be immersed in the battery cups or cells, when the battery is to be used, and withdrawn and supported out of the cups when not in use. The object is to prevent wasting of the plates by standing in the solution. It is a construction generally used with sulphuric acid--chromic acid solution and amalgamated zinc and carbon plates. Battery, Pneumatic. A battery arranged to have air blown through the solution to assist diffusion and depolarization. It is a construction applied to chromic acid or bichromate batteries. Battery, Primary. A battery in which the current is supplied by the solution of one of the plates by the solution. The term distinguishes it from a secondary or storage battery. Battery, Pulvermacher's Electro-Medical. In this battery, the electrodes were zinc and copper wires wound upon small pieces of wood. Dilute vinegar was used as the excitant, because it could be found in every household. Formerly the battery had great success. It is now little used. Battery, Sal Ammoniac. Batteries in which a solution of ammonium chloride is the excitant; they are very extensively used on open circuit work. (See Battery, Leclanché.) The crystals formed in these batteries have been analyzed and found to consist of ammonium zinc chloride, 3 Zn Cl2, 8 N H3, 4 H20. Battery, Salt, or Sea Salt. Batteries in which a solution of sodium chloride or common salt is the excitant, have been largely used, especially for telegraphic purposes. The Swiss telegraphs use a carbon-zinc combination with salt and water as the excitant. The batteries are sometimes mounted as plunge batteries. They are exhausted by short circuiting after some hours, but recuperate on standing. The zinc is not amalgamated. 70 STANDARD ELECTRICAL DICTIONARY. Battery, Sand. A battery whose cells are charged with sand saturated with dilute acid. It prevents spilling of acid. It is now practically obsolete. Fig. 47. SECONDARY BATTERY. Battery, Secondary. A voltaic battery whose positive and negative electrodes are formed or deposited by a current from a separate source of electricity by electrolysis. On disconnection the battery is ready to yield a current, in the reverse direction of that of the charging current. The usual type has lead plates on one of which lead binoxide and on the other of which spongy lead is formed. The lead binoxide seems to be the negative element, and it also acts as the depolarizer. The spongy lead is the positive electrode. The solution is dilute sulphuric acid of specific gravity 1.17. The action consists first in the oxidation of the spongy lead. The hydrogen set free by the reaction, and which by electrolytic transfer goes to the other plate, reduces the lead binoxide to protoxide. The sulphuric acid then attacks the oxides and converts the oxides into sulphates. The charging process consists in sending a current in the reverse direction through the battery. If there are several cells they are arranged in series, so that each one receives the same intensity of current. An electrolytic decomposition takes place, the lead sulphate on one plate is reduced to metallic lead, and that on the other plate is oxidized to lead binoxide. It is then ready for use. 71 STANDARD ELECTRICAL DICTIONARY. The plates in a lead plate battery are of very large area per cell, and are placed close together. Sometimes, as in Planté's battery, large flat plates are laid together with a separating insulator between them, and are then rolled into a spiral. Sometimes, the most usual arrangement, the plates are in sets, the positive and negative ones alternating, and each cell containing a number of plates. To secure a good quantity of active material, the plates are sometimes perforated, and the perforations are filled with oxide of lead. This gives a good depth of material for the charging current to act on, and avoids the necessity for a tedious "forming," q. v. The electro-motive force of such a battery per cell is 2 volts. Its resistance may only be one or two-hundredths of an ohm. An intense current of many amperes can be supplied by it, but to avoid injuring the cell a current far less than the maximum is taken from it. To charge it, a slightly greater electro-motive force, the excess being termed spurious voltage, is required. Fig. 48. SIEMENS' AND HALSKE'S PAPER PULP BATTERY. 72 STANDARD ELECTRICAL DICTIONARY. Battery, Secondary, Plante's. Plante's secondary battery is one of the earlier forms of storage battery, but has had much success. Two lead plates, large in area and close together but not touching, are "formed," by exposure to an electrolyzing current of electricity in one direction, while they are immersed in dilute sulphuric acid. This converts the surface of one plate into binoxide. The cell is then allowed to discharge itself almost completely, when the charging current is again turned on. This process is repeated over and over again, until the surfaces of the plates are considerably attacked, one plate, however, being maintained in a state of oxidation. After a few days of this operation a period of rest is allowed between the reversals, which sets up a local action on the oxidized plate, between the metallic lead of the plate, and its coating of binoxide. This causes the lead to be attacked, under the influence of the local couple, and sulphate of lead is formed, which, ultimately, by the charging current is converted into peroxide. These operations produce an exceedingly good battery. The process described is termed forming. The plates separated by strips of insulating material are generally wound into a double spiral. Battery, Siemens' and Halske's. A Daniell battery of peculiar shape. The copper, C, is at the bottom of the glass jar, A. The inner jar, K, has the form of a bell, and supports a mass of paper pulp, which is dampened with sulphuric acid. The zinc, Z, rests on top of the mass of pulp. The battery is very durable, but of high resistance. Battery, Sir William Thomson's. A form of Daniell battery, of the gravity type. The receptacles are shallow wooden trays lined with lead. A thin plate of copper rests on the bottom. The zinc plate is of gridiron shape, and rests on wooden blocks which support it in a horizontal position above the copper. One tray is placed on top of the other, the upper tray resting on the corners of the zinc plate which rise above the level of the top of the flat vessel. Thus connection is assured without wires or binding posts. It is charged like a gravity battery. The density of the zinc sulphate solution should be between 1.10 and 1.30. The circuit must be kept closed to prevent deposition of metallic copper on the zinc. The entire disposition of the battery is designed to reduce resistance. Battery, Skrivanow. A pocket battery of the De la Rue type, with a solution of 75 parts caustic potash in 100 parts of water as the excitant. The silver chloride is contained in a parchment paper receptacle. Its electro-motive force is 1.45 to 1.5 volts. Battery, Smee's. A single fluid combination, with zinc positive plate, and a plate of silver, coated with platinum black, for the negative plate. The finely divided platinum affords a surface from which the hydrogen bubbles instantly detach themselves, thus preventing polarization. The liquid is a mixture of one part sulphuric acid to seven parts of water. For the negative plate silver-plated copper, coated with platinum black, is used. Electromotive force, .47 volt. Fig. 49. SMEE'S BATTERY. 73 STANDARD ELECTRICAL DICTIONARY. Fig. 50. SPIRAL BATTERY, OR HARE'S DEFLAGRATOR. Battery, Spiral. A battery whose plates of thin zinc and copper are wound into a spiral so as to be very close, but not touching. Dilute sulphuric acid is the excitant. It is now practically obsolete. Synonyms--Calorimeter--Hare's Deflagrator. Battery, Split. A battery of a number of voltaic cells, connected in series, with their central portion grounded or connected to earth. This gives the ends of opposite potentials from the earth, and of difference therefrom equal to the product of one-half of the number of cells employed, multiplied by their individual voltage. Battery Solutions, Chromic Acid. A number of formulae have been proposed for these solutions. (See Electropoion Fluid--Kookogey's Solution--Poggendorff's Solution-- Trouvé's Solution--Delaurier's Solution--Chutaux's Solution--Dronier's Salt--Tissandier's Solution.) Battery, Trough. A battery whose elements are contained in a trough, which is divided by cross-partitions so as to represent cups. A favorite wood for the trough is teak, which is divided by glass or slate partitions. Marine glue or other form of cement is used to make the joints tight. For porous cup divisions plates of porous porcelain or pottery are placed across, alternating with the impervious slate partitions. Battery, Trouvé's Blotting Paper. A battery of the Daniell type in which the solutions are retained by blotting paper. A considerable thickness of blotting paper lies between the two plates. The upper half of the thickness of the blotting paper is saturated with a solution of zinc sulphate, on which the zinc plate rests. The lower half of the paper is saturated with copper sulphate solution, and this rests upon the copper plate. Fig. 51. TROUVÉ'S BLOTTING PAPER BATTERY. 74 STANDARD ELECTRICAL DICTIONARY. Battery, Tyer's. A modification, as regards the positive element, of Smee's battery, q. v. The bottom of the battery jar contains a quantity of mercury in which pieces of zinc are thrown, and this constitutes the positive element. A ball of zinc at the end of an insulated copper wire affords the connection with the zinc and mercury. Its great advantage is that the smallest scraps of zinc can be used in it, by being dropped into the mercury. The negative plate is platinized silver; the exciting liquid, dilute sulphuric acid. Fig. 52. TYER'S BATTERY. 75 STANDARD ELECTRICAL DICTIONARY. Fig. 53. SECTION OF UPWARD'S BATTERY. Fig. 54. ELEVATION OF UPWARD'S BATTERY. Battery, Upward's. A primary voltaic cell, the invention of A. Renée Upward. Referring to the cuts, the positive plate. Z, is of cast zinc; it is immersed in water, in a porous cup, B. Outside of the porous cup and contained in the battery jar are two carbon plates, C, C, connected together. The rest of the space between the porous cup and battery jar is packed with crushed carbon, and the top is cemented. Chlorine gas is led by a pipe, D, into the outer cell. It diffuses through the fine carbon, dissolves in the water, and so finds its way to the zinc, which it attacks, directly combining therewith, and forming zinc chloride (Zn + 2 Cl = Zn Cl 2). Such of the chlorine as is not absorbed finds its way by an outlet tube, E, to the next cell. Arrangements are provided for generating chlorine gas as required. The high specific gravity of the gas is utilized in regulating its distribution through the cells. The electro-motive force of the cell is 2.1 volts. A cell 11.5 by 5.5 inches and 12.5 inches deep has a resistance of 0.2 ohm. An overflow pipe, F, with faucet, T, is supplied to withdraw the solution of zinc chloride as it accumulates. 76 STANDARD ELECTRICAL DICTIONARY. Battery, Varley's. A Daniell battery of the Siemens' and Halske's type (see Battery, Siemens' and Halske's), in which zinc oxide is substituted for the paper pulp of the other battery. It has been very little used. Battery, Volta's. The original acid battery. It has a negative electrode of copper, a positive electrode of zinc; the excitant is sulphuric acid diluted with sixteen times its volume of water. It rapidly polarizes, and is very little used. Battery, Voltaic or Galvanic. An apparatus for converting chemical energy directly into electric energy. This is as broad a definition as can well be given. The general conception of a battery includes the action of electrolysis, a solution in the battery acting upon one of two conducting electrodes immersed in such fluid, which dissolves one of them only, or one more than the other. The best way to obtain a fundamental idea of a battery is to start with the simplest. Dilute sulphuric acid dissolves neither pure zinc nor copper. But it has a far stronger affinity for the first named metal. If now we immerse in dilute acid two plates, one of pure zinc, and one of copper, no action will be discernible. But if the plates are brought in contact with each other a stream of bubbles of hydrogen gas will escape from the surface of the copper and the zinc will dissolve. By applying proper tests and deductions it will be found that the copper and zinc are being constantly charged with opposite electricities, and that these are constantly recombining. This recombination produces what is known as an electric current. To constitute a battery the zinc and copper plates must be connected outside of the solution. This connection need not be immediate. Any conductor which touches both plates will bring about the action, and the current will pass through it. The easiest way to picture the action of a battery is to accept the doctrine of contact action. In the battery the molecules of water are pulled apart. The hydrogen molecules go to the copper, the oxygen molecules go to the zinc, each one, leaving its contact with the other, comes off charged with opposite electricity. This charges the plates, and the continuous supply of charge and its continuous discharge establishes the current. The accumulation of hydrogen acts to stop the action by polarization. Its own affinity for oxygen acts against or in opposition to the affinity of the zinc for the same element, and so cuts down the action. A depolarizer of some kind is used in acid batteries for this reason. As such depolarizer has only to act upon one plate, in most batteries it is usual to surround such plate only, as far as it is possible, with the depolarizer. The solution which dissolves the zinc is termed the excitant or exciting solution. To this concrete notion of a voltaic battery the different modifications described here may be referred. Zinc, it will be seen, forms the almost universally used dissolved plate; carbon or copper forms the most usual undissolved plate; sulphuric acid in one form or another is the most usual excitant. The solution in a voltaic battery is electrolyzed (see Electrolysis). Hence the solutions must be electrolytes. The sulphuric acid and other ingredients play a secondary role as imparting to the battery fluids this characteristic. It is not necessary to have electrodes of different substances, the same metal maybe used for both if they are immersed in different solutions which act differentially upon them, or which act with more energy on one than on the other. Such are only of theoretical interest. 77 STANDARD ELECTRICAL DICTIONARY. Battery, Water. A voltaic battery, whose exciting fluid is water. They are used for charging quadrant electrometer needles and similar purposes. They polarize very quickly and are of high resistance. Hence very small plates in large number can be used without impairing their advantage. Rowland's water battery dispenses with cups and uses capillarity instead. The zinc and platinum or copper plates of a couple are placed very close together, while the couples are more distant. On dipping into water each couple picks up and retains by capillarity a little water between its plates, which forms the exciting fluid. Many hundred couples can be mounted on a board, and the whole is charged by dipping into water and at once removing therefrom. It then develops its full potential difference. Fig. 55. SECTION OF WOLLASTON BATTERY. Fig. 56. PLATES OF WOLLASTON'S BATTERY. 78 STANDARD ELECTRICAL DICTIONARY. Battery, Wollaston. The original plunge battery is attributed to Wollaston. He also invented the battery known by his name, having the disposition shown in the cut, of zinc Z, surrounded by a thin sheet of copper C; o, o', o", are the terminals and B, B, the battery jars. Dilute sulphuric acid is used for exciting fluid. B. A. U. Abbreviation for British Association unit, referring generally to the B. A. unit of resistance. B. A. Unit of Resistance. The original ohm used under that name previous to 1884. The Paris committee of that year recommended as a practical unit what is known as the legal ohm. (See Ohm, Legal.) 1 Legal Ohm = 1.0112 B. A. Units of Resistance. 1 B. A. Unit of Resistance = .9889 Legal Ohms. 1 B. A. Unit of Resistance = .98651E9 C. G. S. units. B. E. adj. British Engineering, a qualification of a set of units, the B. E. units, having for base the foot and pound. The term is but little used. Beaumé Hydrometer. A hydrometer graduated on the following principle: The zero point corresponds to the specific gravity of water for liquids heavier than water. A solution of 15 parts of salt in 85 parts of water corresponds in specific gravity to 15° B., and between that and zero fifteen equal degrees are laid out. The degrees are carried down below this point. The zero points for liquids lighter than water correspond to the specific gravity of a solution of 10 parts of salt in 90 parts of water. The specific gravity of water is taken as 10° B. This gives ten degrees which are continued up the scale. Becquerel's Laws of Thermoelectricity. These are stated under the heads, Law of Intermediate Metals and Law of Successive Temperatures, q. v. Bed Piece. In a dynamo or motor the frame carrying it, including often the standards in which the armature shaft is journaled, and often the yoke or even entire field magnet core. Bell, Automatic Electric. A bell which rings as long as the circuit is closed, having a circuit breaker operated by its own motion. (See Bell, Electric.) Synonyms--Trembling Bell--Vibrating Bell. Bell, Call. A bell operated by electricity, designed to call attention, as to a telephone or telegraphic receiver. (See Bell, Electric.) 79 STANDARD ELECTRICAL DICTIONARY. Bell Call. A calling device for attracting the attention of any one, consisting of some type of electric bell. Bell, Circular. A gong-shaped bell, whose clapper and general mechanism is within its cavity or behind it. Bell, Differentially Wound. An electric bell, whose magnet is wound differentially so as to prevent sparking. Fig 57. AUTOMATIC ELECTRIC BELL. Bell, Electric. A bell rung by electricity. Generally it is worked by a current exciting an electro-magnet, attracting or releasing an armature which is attached to the vibrating or pivoted tongue of the bell. It may be worked by a distant switch or press-button, q. v., ringing once for each movement of the distant switch, etc., or it may be of the vibrating bell type as shown in the cut. When the current is turned on in this case it attracts the armature. As this moves towards the poles of the magnet it breaks the circuit by drawing the contact spring, q. v., away from the contact point, q. v. This opens the circuit, to whose continuity the contact of these two parts is essential. The hammer, however, by its momentum strikes the bell and at once springs back. This again makes the contact and the hammer is reattracted. This action continues as long as the circuit is closed at any distant point to which it may be carried. The ordinary vibrating bell is a typical automatic circuit breaker, q. v., this type keeping up the ringing as long as the circuit is closed. Other bells have no electric contact and simply ring once every time the circuit is closed. Others worked by an alternating current ring once for each change of direction of current. 80 STANDARD ELECTRICAL DICTIONARY. Bell, Electro-mechanical. A bell which has its striking train operated by a spring or descending weight, and which train is thrown into action by the release of a detent or equivalent action by the closing of an electric circuit. It rings for any given time after being started. Bell, Indicating. A bell which by drop-shutter or other indicator connected in circuit with it, indicates its number or other designation of its call. Bell, Magneto. An electric bell operated by the alternating current from a magneto generator. It has a polarized armature and no circuit breaker. The armature is attracted first in one direction and then in the other, as the current alternates and reverses the polarity of the electro-magnet. Bell, Relay. A bell operated by a relay circuit. Bias. In polarized relay the adjustment of the tongue to lie normally against one or the other contact. (See Relay, Polarized.) 81 STANDARD ELECTRICAL DICTIONARY. Fig. 58. RESISTANCE COILS SHOWING BIFILAR WINDING. Bifilar Winding. The method followed in winding resistance coils to prevent them from creating fields of force. The wire is doubled, and the doubled wire starting with the bend or bight is wound into a coil. The current going in opposite senses in the two lays of the winding produces no field of force. Binary Compound. A chemical compound whose molecule contains only two elements, such as water (H2 0), lead oxide (Pb 0), and many others. Binding. In a dynamo or motor armature the wire wound around the coils to secure them in place and prevent their disturbance by centrifugal action. Fig. 59. DOUBLE BINDING POST. Fig. 60. BINDING POST, ENGLISH PATTERN. FIG. 61. WOOD SCREW BINDING POST. Binding Posts or Screws. Arrangements for receiving the loose end of a wire of an electric circuit, and securing such end by a screw. Several constructions are used, as shown here. Sometimes the wire is passed through a hole, and a screw tapped in at right angles to the hole is screwed down upon the wire. Sometimes the wire is clamped between two shoulders, one on the screw, the other on the post. The screw is often a flat-headed thumb screw or has a milled edge. Sometimes the screw has a slot and is turned by a screw-driver. Several openings are often provided in the same post for different wires. Binnacle. The case containing a mariner's compass on shipboard. It is enclosed completely; it has a glass side or window through which the compass can be seen, and is provided with one or two lamps arranged to light the card, while showing as little light as possible outside. 82 STANDARD ELECTRICAL DICTIONARY. Bioscopy, Electric. The diagnosis of life and death by the action of the animal system when subjected to an electric current or electrification. Bismuth. A metal, one of the elements, atomic weight, 210 ; equivalent, 70; valency, 3; specific gravity, 9.9. It is a conductor of electricity. Relative Resistance, compressed, (silver = 1) 87.23 Specific Resistance, 131.2 microhms Resistance of a wire (a) 1 foot long, weighing 1 grain, 18.44 ohms (b) 1 foot long, 1/1000 inch thick, 789.3 " (c) 1 meter long, weighing 1 gram, 12.88 " (d) 1 meter long, 1 millimeter thick, 1.670 " Resistance of a 1-inch cube 51.65 microhms Electro chemical equivalent, .7350 (Hydrogen = .0105) (See Thermo-electric Series.) FIGS. 62, 63. INCANDESCENT WIRE FUSE. ABEL'S PATENT. FIG 64. VON EBNER'S FRICTIONAL ELECTRIC MACHINE FOR EXPLODING ELECTRIC FUSES OR DETONATORS. Bi-telephone. A pair of telephones arranged with a curved connecting arm or spring, so that they can be simultaneously applied to both ears. They are self-retaining, staying in position without the use of the hands. 83 STANDARD ELECTRICAL DICTIONARY. Blasting, Electric. The ignition of blasting charges of powder or high explosives by the electric spark, or by the ignition to incandescence (red or white heat) of a thin wire immersed in or surrounded by powder. Special influence or frictional electric machines or induction coils are used to produce sparks, if that method of ignition is employed. For the incandescent wire a hand magneto is very generally employed. (See Fuse, Electric.) The cuts, Figs. 62 and 63, show one form of incandescent wire fuse. The large wires are secured to the capsule, so that no strand can come upon the small wire within the cavity. The cut, Fig. 64, shows a frictional electric machine for igniting spark fuses. Bleaching, Electric. Bleaching by agents produced or made available by the direct action of electricity. Thus if a current under proper conditions is sent through a solution of common salt (sodium chloride), the electrodes being close together, the salt is decomposed, chlorine going to one pole and sodium hydrate to the other. The two substances react upon each other and combine, forming sodium hypochlorite, which bleaches the tissue immersed in its solution. Block System. A system of signalling on railroads. The essence of the system consists in having signal posts or stations all along the road at distances depending on the traffic. The space between each two signal posts is termed a block. From the signal posts the trains in day time are signalled by wooden arms termed semaphores, and at night by lanterns. The arms may be moved by hand or by automatic mechanism depending in part on electricity for carrying out its functions. Thus in the Westinghouse system the semaphores are moved by pneumatic cylinders and pistons, whose air valves are opened and shut by the action of solenoid magnets, q. v. The current of these magnets is short circuited by passing trains, so as to let the valves close as the train passes the signal post. The block system causes the semaphore to be set at "danger" or "caution," as the train enters the next block. Then the following train is not allowed to enter the block until the safety signal is shown. The Westinghouse system provides for two semaphores on a post, one indicating "danger" as long as the train is on the next block; the other indicating "caution" as long as the train is on the next two blocks. The rails form part of the circuit, their joints being bridged by copper wire throughout the block, and being insulated where the blocks meet. Block Wire. In the block system a wire connecting adjacent block-signal towers or semaphore poles. Blow-pipe. A name sometimes given to an electric experiment illustrating the repulsion of electrified air particles from a point held at high relative potential. A metallic point, placed on the prime conductor of an electric friction or influence machine, becomes highly electrified, and the air becoming excited is repelled and acts upon the candle flame. If the candle is placed on the conductor and a point held towards it the repulsion is still away from the point. 84 STANDARD ELECTRICAL DICTIONARY. Blow-pipe, Electric Arc. A name sometimes given to devices for using the voltaic arc to produce local heating effects. The directive action of the magnet may be used to force out the arc like a blow-pipe flame, or a blast of air may be directly applied for the same purpose. Blue-stone. A trade name for crystallized copper sulphate, used in Daniell's and gravity batteries. Boat, Electric. A boat propelled by electricity. The electricity drives a motor which actuates a screw propeller. The current is generally supplied by a storage battery. When used on rivers charging stations are established at proper places. When the boat is used as a tender or launch for a steam ship, such as a war-vessel, the battery is charged by a plant on board the ship. From their noiselessness electric boats are peculiarly available for nocturnal torpedo operations, and the universal equipment of modern war-ships with electric lightning and power plants makes their use possible at all points. This type is often termed an electric launch, and most or all electric boats fall under this category. Bobbins. A spool of wood or other material wound with insulated wire. In a tangent galvanometer the bobbin becomes a ring, with a channel to receive the winding. As the ring is not infinitely large compared to the needle the tangent law is not absolutely fulfilled. It is most accurately fulfilled (S. P. Thomson) when the depth of the groove or channel in the radial direction bears to the breadth in the axial direction the ratio of square root of 3 to the square root of 2 or approximately 11 : 9 Body Protector. A metallic short circuit connected with the wrists and lower legs of the human body, so that if by accident an active circuit is grounded by the hands and body of the workman wearing it, most of the current will pass through the wire conductors, thus avoiding the vital organs of the body. Boiler Feed, Electric. An apparatus by which an electric current acting on an electro-magnet, or other equivalent device, opens the water supply when the water level in a boiler sinks too low, and cuts off the water supply as the water level rises. Boiling. In secondary batteries the escape of hydrogen and oxygen gas when the battery is charged. The bubbling of the escaping gases produces the effect of boiling. 85 STANDARD ELECTRICAL DICTIONARY. Boll. An absolute, or c. g. s., unit of momentum; a gram moving at the rate of one centimeter per second; a gram-kine (see Kine); a unit proposed by the British Association. Bolometer. An apparatus for detecting small amounts of radiant energy (radiant heat, so called). A coil suspended by a fine wire or filament so as to be free to rotate under the effect of force is made up of two parallel and equal wires, insulated from each other, but connected so that parallel currents sent through them go in opposite direction through each. This coil is hung in a strong electro-magnetic field produced by a large coil surrounding it. When a current passes through the suspended coil no effect will follow, because the oppositely wound portions counteract each other exactly. In the circuit with one half of the suspended coil is an exceedingly thin strip of platinum wire. The other half of the coil has no strips. Both halves unite after leaving the coil. If now the strip of platinum is heated its conductivity is affected and its half of the coil receives less current than the other half. This disturbs the balance and the coil swings through a small arc. This apparatus may be made very sensitive, so that an increase of temperature of 1/1400º F., 9/70000°C. (1/14000º F.) will be perceptible. Another construction takes the form of a Wheatstone Bridge, q. v., in whose arms are introduced resistances consisting of bands of iron, .5 Millimeter wide (.02 inches), .004 millimeter (.00016 inch) thick, and folded on themselves 14 times so as to make a rectangular grating, 17 x 12 millimeters (.68 x .48 inch). The least difference of heat applied to the grating affects the galvanometer. Synonym-Thermic Balance. Boreal Pole. The south pointing pole of the magnet. (See Austral Pole.) Bot. A colloquial expression for the English Board of Trade unit of Electrical Supply. It is formed of the initials of the words "Board of Trade." (See Unit, Board of Trade.) Box Bridge. A constriction of Wheatstone's Bridge in which the necessary resistance coils are contained in a single box with plugs for throwing the coils in and out of circuit, and connections to bring the coils into the different arms of the system. The cut shows a box bridge. Connections for the galvanometer, battery wires, and terminals of the unknown resistance are provided, by which its resistances and the connections are brought into the exact relations indicated in the conventional diagram of Wheatstone's bridge. (See Wheatstone's Bridge.) Referring to the cut, the battery wire, say from the zinc plate, connects at A1, thereby reaching A, its true connecting point. To B1 one end of the galvanometer circuit or lead is attached, thereby reaching B, its true connecting point. To C are connected the other end from the galvanometer and one end of the unknown resistance. The other end of the unknown resistance, and the other end of the battery wire, in this case from the carbon plate, connect to D. At G is an infinity plug, as it is called. When out it breaks the circuit. In use after the connections are made the key is depressed and the galvanometer observed. The resistance is changed until no action of the galvanometer is produced by closing the circuit when the ratio of the resistances of the arms gives the proportion for calculating the unknown resistances. Synonym--Commercial Wheatstone Bridge, or commercial form of same. Fig. 65. TOP OF BOX BRIDGE. 86 STANDARD ELECTRICAL DICTIONARY. Boxing the Compass. Naming the thirty-two points of the compass in order, and in sequence to any point called out at random. There are many exercises in the relative sailing points and bearings that come under the same head. Thus the direction of two given points being given by names of the compass points, it may be required to state the number of points intervening. Brake, Electro-magnetic. A brake to stop a wheel from rotating. It comprises a shoe, or sometimes a ring, which by electro-magnetic attraction is drawn against the rotating wheel, thus preventing it from turning, or tending to bring it to rest. (See Electro-magnet, Annular.) Fig. 66. ELECTRIC BRAKE. 87 STANDARD ELECTRICAL DICTIONARY. Branch. A conductor branching from a main line. Sometimes the term is restricted to a principal conductor, from which current is distributed. Branch Block. In electric wiring of buildings, a block of porcelain or other material with grooves, holes and screws for the connection of branch wires to a main wire. Its functions are not only to afford a basis for connecting the wires, but also to contain safety fuses. As when a branch wire is taken off, fuses have to be put in its line, the branch block carries these also. One end of each fuse connects with a main wire, the other end connects with one of the wires of the branch leader or wire. Porcelain is a favorite material for them, as the fusing or "blowing out" of the safety fuses cannot set it on fire. Branch Conductor. A parallel or shunt conductor. Brazing, Electric. Brazing in which the spelter is melted by means of electricity; either current incandescence or the voltaic arc may be used. It is identical in general with electric welding. (See Welding, Electric.) Branding, Electric. A system of branding in which the heat of electrically ignited or incandescent conductors is used to produce or burn in the marks upon the surface. For the alternating current a small transformer is connected to or forms part of the tool. 88 STANDARD ELECTRICAL DICTIONARY. Brassing. The deposition of a coating of brass by electrolysis. The plating bath contains both copper and zinc. As anode a plate of brass is used. The operation must be constantly watched. The deposition of both metals goes on simultaneously, so that a virtual alloy is deposited. By changing the depth of immersion of the anode the color of the deposit is varied. As a formula for a brassing bath the following are typical. They are expressed in parts by weight. (a) For iron and steel. I. Sodium Bisulphate, 200 Potassium Cyanide, 70 per cent., 500 Sodium Carbonate, 1,000 Water, 8,000 II. Copper Acetate, 125 Zinc Chloride, 100 Water, 2,000 Add the second solution to the first. (b) For zinc. I. Sodium Bisulphate, 700 Potassium Cyanide, 70 per cent., 1,000 Water, 20,000 II. Copper Acetate, 350 Zinc Chloride, 350 Aqua Ammoniae, 400 Water, 5,000 Add the second solution to the first. Use a brass anode; add more zinc to produce a greenish color; more copper for a red color. A weak current gives a red color; a strong current lightens the color. The battery power can be altered, a larger or smaller anode can be used, or a copper or zinc anode can be used to change the color of the deposit. The bath may vary from 1.036 to 1.100 sp. gr., without harm. Break. A point where an electric conductor is cut, broken, or opened by a switch or other device, or simply by discontinuity of the wires. Break-down Switch. A switch used in the three-wire system to provide for the discontinuance of the running of one of the dynamos. By connecting the positive and negative bus wires to one terminal of the active dynamo, and the neutral bus wire to the other terminal, one dynamo will supply the current and the system operates like a two-wire system, but can only be used for half its normal capacity. Breaking Weight. The weight which, applied in tension, will break a prism or cylinder, as an electric current conductor. 89 STANDARD ELECTRICAL DICTIONARY. Breath Figures, Electric. If a conductor is electrified and placed upon a piece of glass, it will electrify the glass in contact with it by conduction or discharge. On removing the conductor the glass remains electrified. The localized electrification is shown by breathing gently on the glass, when a species of image of the conductor is produced by the condensed moisture. A coin is often used for conductor. Breeze, Electric. A term in medical electricity, used to designate the silent or brush discharge of high tension electricity. As an instance of its employment, the electric head bath (see Bath, Electric Head,) may be cited. The patient forming one electrode, being insulated and connected to one of the conductors, the other conductor, on being brought near his person, discharges into his body. Bridge. (a) A special bar of copper connecting the dynamos to the bus wire, q. v., in electric lighting or power stations. (b) Wheatstone's bridge, q. v., and its many modifications, all of which may be consulted throughout these pages. British Association Bridge. The type of Wheatstone bridge used by the committee of the association in determining the B. A. ohm; the meter bridge, q. v. Broadside Method. A method of determining the magnetic moment of a magnet. The magnet, n, s, under examination is fixed so that it is at right angles to the magnetic meridian, M, R, which passes through its own center and that of a compass needle. From the deflection of the latter the moment is calculated. FIG 67. BROADSIDE METHOD. Bronzing. In electro-plating the deposition of a mixture or virtual alloy of copper and tin. In general manipulation it resembles the operation of depositing gold and silver alloy, or of brassing. For bronzing the following bath is recommended: Prepare each by itself (a) a solution of copper phosphate and (b) a solution of stannous chloride in a solution of sodium pyrophosphate. For a, dissolve recently precipitated copper phosphate in concentrated solution of sodium pyrophosphate. For b, add to a saturated solution of sodium pyrophosphate solution of stannous chloride as long as the precipitate which is formed dissolves. Of these two solutions add to a solution of sodium pyrophosphate which contains about 1.75 oz. of the salt to the quart, until the precipitate appears quickly and of the desired color. For anodes use cast bronze plates. Sodium phosphate must be added from time to time; if the deposit is too light add copper solution, if too dark add tin solution. (W. T. Brannt.) 90 STANDARD ELECTRICAL DICTIONARY. Brush. In electric current generators and motors, the pieces of copper or other material that bear against the cylindrical surface of the commutator are thus termed. Many different constructions have been employed. Some have employed little wheels or discs bearing against and rotating on the surface of the commutator. A bundle of copper strips is often employed, placed flatwise. Sometimes the same are used, but are placed edgewise. Wire in bundles, soldered together at their distant ends have been employed. Carbon brushes, which are simply rods or slabs of carbon, are used with much success. Synonym--Collecting Brush. Brush, Carbon. A brush for a dynamo or motor, which consists of a plate or rod of carbon, held in a brush holder and pressed against the commutator surface. Brushes, Adjustment of. In electric current generators and motors, the brushes which bear upon the commutator when the machine is in action need occasional adjustment. This is effected by shifting them until sparking between them and the commutator is nearly or quite suppressed. Fig. 68. BRUSH HOLDER. Brushes, Lead of. In a dynamo electric generator, the lead or displacement in advance of or beyond the position at right angles to the line connecting the poles of the field magnet, which is given the brushes. In a motor the brushes are set back of the right angle position, or are given a negative lead. (See Lag.) 91 STANDARD ELECTRICAL DICTIONARY. Brush Holders. The adjustable (generally) clutch or clamps for holding the commutator brushes of a dynamo, which keep them in contact with the commutator, and admit of adjustment by shifting backward and forward of the brushes to compensate for wear. They are connected to and form part of the rocker, q. v. By rotating the latter the brush-holders and brushes are carried in one direction or other around the commutator, so as to vary the lead as required. Brush, Pilot. A third brush, used for application to different parts of a revolving armature commutator to determine the distribution of potential difference between its different members. (See Curve of Distribution of Potential in Armature.) One terminal of a volt-meter is connected to one of the regular brushes, A, of a dynamo; the other to a third brush, p, which is pressed against different portions of the commutator of the dynamo. The readings of the volt-meter are plotted in a curve of distribution of potential. Fig. 69. PILOT BRUSH. Brush, Rotating. Brushes for taking off the current from dynamo commutators, or giving current connection to motors, whose ends are in the form of rollers which rotate like little wheels, and press against the commutator surface. Brush, Third. A third brush is sometimes provided in a dynamo for regulating purposes. Applied to a series machine it adjoins one of the regular brushes and delivers its current to a resistance, to whose further end the regular circuit is connected. By a sliding connection the resistance is divided between the third brush circuit and the regular circuit, and by varying the position of this contact regulation is obtained. It is to be distinguished from the pilot brush used for determining the characteristic of the commutator, although based on the same general principles. Fig. 70. THIRD BRUSH REGULATION. 92 STANDARD ELECTRICAL DICTIONARY. Brush, Wire Gauze. A collecting or commutator brush for a dynamo or motor, which brush is made of wire gauze rolled up and compressed into shape. Buckling. The bending up and distortion of secondary battery plates. It is largely due to over-exhausting the batteries. Where the E. M. F. is never allowed to fall below 1.90 volt it is far less liable to occur. Bug. Any fault or trouble in the connections or working of electric apparatus. Bug Trap. A connection or arrangement for overcoming a "bug." It is said that the terms "bug" and "bug trap" originated in quadruplex telegraphy. Bunsen Disc. In photometry, the Bunsen Disc is a piece of paper upon whose centre a spot is saturated with melted paraffin, or a ring of paraffined surface surrounds an untouched central spot. If placed in such a position that it receives an equal illumination on each side, the spot almost disappears. It is used on the bar photometer. (See Photometer, Bar.) Synonym--Grease Spot. 93 STANDARD ELECTRICAL DICTIONARY. Buoy, Electric. A buoy for use to indicate channels or dangers in harbors and elsewhere, which carries an electric light, whose current is supplied by cable from shore. It has been proposed to use glass tubes exhausted of air and containing mercury, which, as moved by the waves, would produce a luminous effect. A fifty-candle power incandescent lamp is an approved source of light. Burner, Electric Gas. A gas burner arranged for the flame to be lighted by electricity. It takes a great variety of forms. In some cases a pair of terminals are arranged near the flame or a single terminal is placed near the metal tip, the latter forming one of the terminals. The spark is generally produced by an induction coil, or a spark coil. The gas may first be turned on and the spark then passed. Sometimes the turning of the gas cock of an individual burner makes and breaks a contact as it turns, and thereby produces simultaneously with the turning on of the gas a spark which lights it. Another form is wholly automatic. A pair of electro-magnets are attached below the base of the burner, one of which, when excited, turns on the gas, and the other one when it is excited turns it off. At the same time a spark is produced with the turning on of the gas so that it is lighted. Thus, by use of a automatic burner, a distant gas burner can be lighted by turning an electric switch. An out-door lamp may be lighted from within a house. The increasing use of electric incandescent lamps, lighted by the turning of a switch, tends to displace electric gas burners. The latter have been classified into a number of types depending on their construction. Burners are sometimes connected in series with leads from an induction coil. Then the gas is turned on all at once, and a succession of sparks passed until the gas is all lighted. The ignition is practically instantaneous. Button, Push. A species of switch which is actuated by the pressure of a button. In its normal position the button is pressed outwards by a spring, and the circuit is open. When pressed inwards, it closes the circuit. When released it springs backward and opens the circuit again. They are principally used for ringing bells. If the latter are of the automatic type, they ring as long as the button is pressed. For door-bells and room-bells, the button often occupies the center of a rosette of wood or bronze or other ornamental piece. Sometimes, as shown in the cut, they are constructed for use on floors to be pressed by the foot. The general principle of their construction is shown, although the method of making the contact varies. Synonym--Press Button. Fig. 71. FLOOR PUSH BUTTON. 94 STANDARD ELECTRICAL DICTIONARY. Burning. (a) In a dynamo, the production of shifting and temporary arcs between the commutator and brushes, which arcs produce heat enough to injure the parts in question. (b) In electro-plating, a defect due to too strong a current in proportion to the strength of solution and area of electrodes. This gives a black or badly-colored deposit. Bus Rod. A copper conductor used in electric lighting or power stations, to receive the current from all the dynamos. The distributing leads are connected to the bus wires. In the three-wire system there are three; in the two-wire system there are two bus wires. The name is undoubtedly derived from "omnibus." The bus wires may be divided into positive, negative, and, in the three-wire system, neutral bus wires. Synonyms--Omnibus Rod, Wire, or Bar--Bus Bar, or Wire. Buzzer. An electric alarm or call produced by a rapid vibration of electric make and break mechanism, which is often magnified by enclosure in a resonating chamber, resembling a bell, but which is not struck or touched by the vibrating parts. Sometimes a square wooden box is used as resonator. Fig. 72. BUZZER. 95 STANDARD ELECTRICAL DICTIONARY. B. W. G. Abbreviation for Birmingham Wire Gauge. (See Wire Gauge, Birmingham.) C. (a) Abbreviation for Centigrade, as 100 C., meaning 100 Centigrade. (See Centigrade Scale.) (b) A symbol of current or of current strength. Thus in the expression of Ohm's law C = E/R. C indicates current strength or intensity, not in any fixed unit, but only in a unit of the same order in which E and R are expressed; E Indicating electro-motive force and R resistance. Cable. (a) Abbreviation for Cablegram, q. v. (b) v. It is also used as a verb, meaning to transmit a message by submarine cable. (c). An insulated electric conductor, of large diameter. It often is protected by armor or metallic sheathing and may be designed for use as an aerial, submarine, subterranean or conduit cable. A cable often contains a large number of separately insulated conductors, so as to supply a large number of circuits. Cable, Aerial. A cable usually containing a large number of separately insulated wires, and itself insulated. It is suspended in the air. As its weight is sometimes so great that it could not well sustain it, a suspending wire is in such cases carried along with it, to which it is suspended by cable hangers, q. v. Cable Box. A box for receiving underground cable ends and connecting the separate wires of the cable to air-line wires. It is often mounted on a pole, which forms the starting point of the air-line portion of the system. Cable, Bunched. A cable containing a number of separate and individual conductors. In some forms it consists virtually of two or more small cables laid tangent to each other and there secured. Thus each in section represents two or more tangent circles with the interstice solidly filled with the metal sheathing. Cable, Capacity of. The electrostatic capacity of a cable. A cable represents a Leyden jar or static condenser. The outer sheathing or armor, or even the more or less moist coating, if it is unarmored, represents one coating. The wire conductors represent the other coating, and the insulator is the dielectric. The capacity of a cable interferes with its efficiency as a conductor of broken or interrupted currents, such as are used in telegraphy or telephoning. As each impulse or momentary current is sent into the line, it has to charge the cable to at least a certain extent before the effects of the current are perceptible at the other end. Then the cable has to discharge itself. All this creates a drag or retardation. The capacity of a cable is used to determine the locality of breaks in the continuity of the conductors. The capacity per unit of length being accurately known, it is obvious that, if the conductor breaks without disturbance of the insulator, the distance of the break from the end can be ascertained by determining the capacity of the cable from one end. This capacity will be in proportion to the capacity of a mile, a knot or any fixed unit, as the distance to the break is to the length used as standard. 96 STANDARD ELECTRICAL DICTIONARY. Cable Core. The conductors of a cable. They are generally copper wire. In a telephone cable they may be very numerous and insulated from each other. In ocean cables they may be a group of bare wires twisted or laid together. Sometimes the conductors are arranged for metallic circuits, each pair being distinguished by special colored windings. Cable, Duplex. A cable containing two wires, each with separate insulation, so as to be virtually two cables, laid and secured parallel and side by side. Cable, Flat. A cable, flat in shape, so as to lie closely against a wall or ceiling. Cablegram. A message which has been transmitted or is to be transmitted by a submarine cable. It is sometimes called a cable. Cable Grip. A grip for holding the end of a cable, when the cable is to be drawn into a conduit in a subway. It is an attachment to provide the cable with an eye or loop. Its end is a split socket and embraces the end of the cable, and is secured thereto by bolts driven through the cable end. In drawing a cable into a conduit a capstan and rope are often used, and the rope is secured to the cable end by the grip. Fig. 73. CABLE HANGER, CABLE, AND SUSPENDING WIRE. Fig. 74. CABLE HANGER, OPEN. Cable Hanger. When a heavy electric cable is suspended from poles it often would be unsafe to trust to its longitudinal strength to support or sustain its own weight unless the poles were very near together. In such case an auxiliary or sustaining wire is run along with it, and by clips or hangers the cable is connected thereto at as frequent intervals as seem desirable. The contrivance may take the form of a strip of metal surrounding the cable and carrying a hook or eye through which the supporting wire passes. Synonym--Cable Clip. 97 STANDARD ELECTRICAL DICTIONARY Cable Hanger Tongs. Tongs for attaching cable hangers, q.v. They have long handles so as to be worked from the ground at the middle of a span. Cable, Suspending Wire of. A wire by which an aerial cable is in part or entirely suspended. The cable, being incapable of sustaining its own weight, is secured by clips or hangers to a wire, strong from pole to pole immediately above it. (See Cable Hanger.) Cable Tank. A tank in which a submarine cable is coiled away on board a cable-laying ship, or in the factory on shore for the purpose of testing or watching its insulation. Sometimes, in order to test it under pressures approximating to those it will be subjected to in practice, the tank is closed and the portion of cable within it is subjected to hydraulic pressure. This represents the pressure it will be exposed to in deep water. Calamine. A mineral; zinc silicate; formula Zn2 Si 03, crystalline system, Orthorhombic; specific gravity, 3.16-3.9. The crystals often show strong pyroelectric properties. Calibration. The determination by experiment or calculation of the value of the readings of an instrument, such as a galvanometer or eudiometer. Thus if a tangent galvanometer has its circle graduated in degrees, a table of the value of tangents corresponding to every reading occurring in practice would represent a calibration by calculation. A determination of the current required to produce each deflection would be a calibration in the more usual sense. Calibration is generally absolute, as referring to some fixed unit, but it may be relative, as between two things both of unknown absolute value. Calibration, Absolute. The determination of the absolute value of currents producing given deflections in a galvanometer, or in other instruments the determination of corresponding values, as the instrument may be a magnetometer, quadrant electrometer, or other apparatus. Calibration, Invariable. Calibration applicable to specially constructed galvanometers, which is unaffected by the proximity of masses of iron or field magnets. Such galvanometers must have a constant controlling field. Such is given by a powerful permanent magnet, whose field is practically unaffected by the causes named. Or else, in place of a controlling field, a spring maybe used to which the needle is attached, and which tends to hold it in one position. 98 STANDARD ELECTRICAL DICTIONARY. Calibration, Relative. The determination of the law connecting the various indications of an instrument, such as the deflections of the needle of a galvanometer, with the relative causes; in the case of a galvanometer, the strength of the currents or the electro-motive forces producing them directly or indirectly. Call Bell. A bell rung by pressing a button or otherwise to call the attention of a person in a distant place. They can be classified into a great variety of types according to their uses or construction. Call Button. A push button used for ringing a call bell, sounding a buzzer, working an annunciator and for similar purposes. (See Push Button.) Synonym--Push Button. Calling Drop. In a telephone exchange or telegraph office a drop shutter annunciator, which falls to call the attention of the operator, notifying him that the line connected to such drop is to be connected to some other circuit. Calorie or Calory. A practical unit of heat. There are two calories, respectively called the great and the small calorie, or the kilogram and the gram calorie. The first is the quantity of heat required to raise the temperature of one kilogram of water one degree centigrade. The second is the quantity of heat required to raise the temperature of one gram of water one degree centigrade. Calorimeter. An apparatus for measuring the quantity of heat evolved or produced by or under different conditions. Dulong's water calorimeter consists of a water jacket, and by the increase of temperature of the water and enclosing vessels the amount of heat produced by anything in the inner vessels is determined. The amount of ice a heated body will melt is sometimes made the basis of a calorimeter. The expansion of a fluid, as water, may be used. In the calorimeter shown in the cut the heat produced in a conductor by the passage of an electric current is caused to heat water whose temperature is shown by a thermometer immersed therein. The increase of temperature and the weight of the water give the basis for a determination of the heat produced by the current. Knowing the resistance of the conductor immersed, the watts can be calculated. This gives the bases for the determination of the heat-equivalent of electric energy. This is but an imperfect calorimeter, as it constantly would lose heat by the surrounding atmosphere, and would cease to operate as a calorimeter when the water was as hot as the wire normally would be, for then it would not absorb all the heat. Fig. 75. CALORIMETER. 99 STANDARD ELECTRICAL DICTIONARY. Candle. The generally accepted unit of illuminating power; there are three kinds in use as standards. (See Candle, Decimal--Candle, German Standard--Candle, Standard.) Candle, Concentric. An electric candle of the Jablochkoff type, having a small solid carbon inside of an outside tubular carbon, the space between being filled with refractory material corresponding to the colombin, q. v., of the ordinary type. The arc springs across from one carbon to the other. Candle, Debrun. An arc lamp with approximately parallel carbons. A transverse priming connects their bases, and the arc starting there at once flies out to the end. Candle, Decimal. A standard of illuminating power, proposed to the Congress of Electricians of 1889 by Picou. It is one-twentieth of a Viole, or almost exactly one standard candle. (See Viole's Standard of Illuminating Power.) Candle, Electric. An arc lamp regulated by simple gravity, or without any feed of the carbons or special feeding apparatus, generally for the production of an arc light of low intensity. This definition may be considered too elastic, and the word may be restricted to parallel carbon lamps in which the arc springs across from carbon to carbon. For the latter class an alternating current is used to keep the carbons of equal length. They are but little used now. Various kinds have been invented, some of which are given here. Candle, German Standard. A standard of illuminating power used in Germany. It is a paraffin candle, 6 to the pound, 20 millimeters diameter; flame, 56 millimeters high; rate of consumption, 7.7 grams per hour. Its value is about two per cent. lower than the English standard candle. 100 STANDARD ELECTRICAL DICTIONARY. Candle Holder. A clamp for holding electric candles of the Jablochkoff type. The ones shown in the cut designed for Jablochkoff candles comprise a pair of metallic clamps, each member insulated from the other, and connected as terminals of the circuit. When the candle is placed in position the metal pieces press against the carbons of the candle and thus convey the current. Below each member of the clamps is a binding screw for the line wire terminals. Fig. 76. JABLOCHKOFF CANDLE HOLDERS. Fig. 77. JABLOCHKOFF CANDLE. Candle, Jablochkoff. An arc lamp without regulating mechanism, producing an arc between the ends of parallel carbons. It consists of two parallel rods of carbon, between which is an insulating layer of non-combustible material called the colombin. Kaolin was originally employed for this part; later, as the fusion of this material was found to short- circuit the arc, a mixture of two parts of calcium sulphate and one of barium sulphate was used. The carbons are 4 millimeters (.16 inch) thick, and the colombin is 3 millimeters (.12 inch) wide and two-thirds as thick. A little slip of carbon is placed across the top, touching both carbons to start the arc. Once started the candle burns to the end, and cannot be restarted after ignition, except by placing a short conductor across the ends, as at first. The Jablochkoff candle may now be considered as virtually extinct in this country. In France at one time a great number were in use. To keep the carbons of equal length an alternating current must always be used with them. Special alternating combinations were employed in some cases where a direct current had to be drawn upon. Candle, Jamin. An arc lamp with approximately parallel carbons, one of which oscillates and is controlled by an electro-magnet and armature. A coil of wire is carried around the carbons to keep the arc steady and in place. The frame and wire coils have been found unsatisfactory, as causing a shadow. Candle Power. The amount of light given by the standard candle. The legal English and standard American candle is a sperm candle burning two grains a minute. It should have burned some ten minutes before use, and the wick should be bent over and have a red tip. Otherwise its readings or indications are useless. A sixteen candle power lamp means a lamp giving the light of sixteen candles. The candle power is a universal unit of illuminating power. 101 STANDARD ELECTRICAL DICTIONARY. Candle Power, Rated. The candle power of arc lamps is always stated in excess of the truth, and this may be termed as above. A 2000 candle power lamp really gives about 800 candles illumination. Synonym--Nominal Candle Power. Candle Power, Spherical. The average candle power of a source of light in all directions. An arc lamp and an incandescent lamp vary greatly in the intensity of light emitted by them in different directions. The average of a number of determinations at various angles, the lamp being moved about into different positions, is taken for the spherical candle power. Candle, Standard. A standard of illuminating power. Unless otherwise expressed the English standard sperm candle is indicated by this term. (See Candle Power.) Candle, Wilde. An arc lamp with approximately parallel carbons. One of the carbons can rotate through a small arc being pivoted at its base. This oscillation is regulated by an electro-magnet at its base, and the carbons touch when no current is passing. They separate a little when the current passes, establishing an arc. The regulation is comparable to that of a regular arc lamp. Fig. 78. WILDE CANDLE. Caoutchouc. India rubber; a substance existing in an emulsion or solution in the juice of certain trees and vines of the tropics, whence it is obtained by coagulation and drying. The name "rubber" is due to the fact that one of its earliest uses was for erasing pencil marks by rubbing. It has a very high value as an insulator. The unworked crude rubber is called virgin gum; after working over by kneading, it is termed masticated or pure gum rubber; after mixture with sulphur and heating, it is termed vulcanized rubber. If enough sulphur is added it becomes hard, and if black, is termed ebonite; if vermilion or other pigment is also added to produce a reddish color, it is termed vulcanite. The masticated gum dissolves more or less completely in naphtha (sp. gr., .850) benzole, turpentine, chloroform, ether and other similar liquids.. The resistance per centimeter cube of "Hooper's" vulcanized India rubber, such as is used in submarine cables is 1.5E16 ohms. The specific inductive capacity of pure India rubber is 2.34--of vulcanized 2.94 (Schiller). Synonyms--India Rubber--Rubber. 102 STANDARD ELECTRICAL DICTIONARY. Capacity, Dielectric. The capacity of a dielectric in retaining an electrostatic charge; the same as Specific Inductive Capacity. 'The number expressing it is sometimes called the dielectric constant. (See Capacity, Specific Inductive.) Capacity, Electric, or Electrostatic. The relative capacity of a conductor or system to retain a charge of electricity with the production of a given difference of potential. The greater the charge for a given change of potential, or the less the change of potential for a given charge the greater the capacity. The measure of its capacity is the amount of electricity required to raise the potential to a stated amount. The unit of capacity is the farad, q. v. Electric capacity is comparable to the capacity of a bottle for air. A given amount of air will raise the pressure more or less, and the amount required to raise its pressure a stated amount might be taken as the measure of capacity, and would be strictly comparable to electrostatic charge and potential change. The capacity, K, is obviously proportional to the quantity, Q, of the charge at a given potential, E, and inversely proportional to the potential, E, for a given quantity, Q, or, (1) K == Q/E and (2) Q = K * E, or, the quantity required to raise a conductor by a given potential is equal to the capacity of the conductor or system multiplied by the rise of potential. The capacity of a conductor depends upon its environments, such as the nature of the dielectric surrounding it, the proximity of oppositely charged bodies and other similar factors. (See Dielectric-Condenser-Leyden jar.) The dimensions of capacity are found by dividing a quantity of electricity by the potential produced in the conductor by such quantity. Quantity ( ((M^.5)*(L^1.5)) / T ) / potential ( ((M^.5)*(L^.5)) / T ) = L. Capacity, Instantaneous. The capacity of a condenser when connected only for an instant to a source of electricity. This is in contrast to electric absorption (see Absorption, Electric), and is capacity without such absorption taking part in the action. 103 STANDARD ELECTRICAL DICTIONARY. Capacity of a Telegraph Conductor. The electric capacity of a telegraphic conductor is identical in quality with that of any other conductor. It varies in quantity, not only for different wires, but for the same wire under different environments, as the wire reacting through the surrounding air or other dielectric upon the earth, represents one element of a condenser, the earth, in general, representing the other. Hence, a wire placed near the earth has greater capacity than one strung upon high poles, although the wires may be identical in length, material and diameter. The effect of high capacity is to retard the transmission of intermitting signals. Thus, when--as in the Morse system--a key is depressed, closing a long telegraph current and sending a signal into a line, it is at least very probable that a portion of the electricity travels to the end of the wire with the velocity of light. But as the wire has to be charged, enough current to move the relay may not reach the end for some seconds. Capacity of Polarization of a Voltaic Cell. The relative resistance to polarization of a voltaic cell, measured by the quantity of electricity it can supply before polarization. A counter-electromotive force may be developed, or the acid or other solution may become exhausted. The quantity of electricity delivered before this happens depends on the size and type of cell and other factors. Capacity, Residual. When two insulated conductors are separated by a dielectric, and are discharged disruptively by being connected or nearly connected electrically, on removing the discharger it is found that a slight charge is present after a short interval. This is the residual charge. (See Charge, Residual.) Shaking or jarring the dielectric facilitates the complete discharge. This retaining of a charge is a phenomenon of the dielectric, and as such, is termed residual capacity. It varies greatly in different substances. In quartz it is one-ninth what it is in air. Iceland spar (crystalline calcite) seems to have no residual capacity. The action of shaking and jarring in facilitating a discharge indicates a mechanical stress into which the electrostatic polarization of the conductor has thrown the intervening dielectric. Capacity, Specific Inductive. The ratio of the capacity of a condenser when its plates are separated by any substance to the capacity of the same condenser when its plates are separated by air. A static accumulator consists of two conducting surfaces separated by an insulator. It is found that the capacity of an accumulator for an electric charge, which varies with or may be rated by the potential difference to which its conductors will be brought by the given charge, varies with the nature of the interposed dielectric, and is proportional to a constant special to each substance. This constant is the specific inductive capacity of the dielectric. The same condenser will have a higher capacity as the dielectric is thinner, other things being equal. But different dielectrics having different specific inductive capacities, the constant may be determined by ascertaining the relative thicknesses of layers having the same total inductive capacity. The thicker the layer, the higher is its specific inductive capacity. Thus it is found that 3.2 units thickness of sulphur have the same total inductive capacity as 1 unit thickness of air. In other words, if sulphur is interposed between two conducting plates, they may be separated to over three times the distance that would be requisite to retain the same capacity in air. Hence, sulphur is the better dielectric, and air being taken as unity, the specific inductive capacity of sulphur is 3.2. 104 STANDARD ELECTRICAL DICTIONARY. The specific inductive capacity of a dielectric varies with the time and temperature. That of glass rises 2.5 per cent. between 12° C. (53.6° F.) and 83° C. (181.4° F.). If a condenser is discharged disruptively, it retains a small residual charge which it can part with later. If a metallic connection is made between the plates, the discharge is not instantaneous. Vibration shaking and jarring facilitate the complete discharge. All this shows that the charge is a phase of the dielectric itself, and indicates a strained state into which it is brought. The following table gives the specific inductive capacity of various substances: Specific Inductive Capacity. Substance Specific Inductive Authority Capacity. Vacuum, air at about 0.001 millimeters pressure 0.94 about Ayrton Vacuum, air at about 5 millimeters 0.9985 Ayrton 0.99941 Boltzmann Hydrogen at about 760 millimeters pressure 0.9997 Boltzmann 0.9998 Ayrton Air at about 760 millimeters pressure 1.0 Taken as the standard Carbon Dioxide at about 760 millimeters pressure 1.000356 Boltzmann 1.0008 Ayrton Olefiant Gas at about 760 millimeters pressure 1.000722 Boltzmann Sulphur Dioxide at about 760 millimeters pressure 1.0037 Ayrton Paraffin Wax, Clear 1.92 Schiller 1.96 Wüllner 1.977 Gibson and Barclay 2.32 Boltzmann Paraffin Wax, Milky 2.47 Schiller India Rubber, Pure 2.34 Schiller India Rubber, Vulcanized 2.94 Schiller Resin 2.55 Boltzmann Ebonite 2.56 Wüllner 2.76 Schiller 3.15 Boltzmann Sulphur 2.88 to 3.21 Wüllner 3.84 Boltzmann Shellac 2.95 to 3.73 Wüllner Gutta percha 4.2 Mica 5 Flint Glass, Very light 6.57 J. Hopkinson Flint Glass, Light 6.85 J. Hopkinson Flint Glass, Dense 7.4 J. Hopkinson Flint Glass, Double extra dense 10.1 J. Hopkinson 105 STANDARD ELECTRICAL DICTIONARY. Capacity, Unit of. The unit of capacity is the capacity of a surface which a unit quantity will raise to a unit potential. The practical unit is the surface which a coulomb will raise to one volt, and is called the farad, q. v. Capacity, Storage. In secondary batteries the quantity of electrical current which they can supply when charged, without undue exhaustion. It is expressed in ampere-hours. The potential varies so little during the discharge that it is assumed to be constant. Capillarity. The reaction between liquid surfaces of different kinds or between liquid and solid surfaces due to surface tension. Its phenomena are greatly modified by electric charging, which alters the surface tension. Capillarity is the cause of solutions "creeping," as it is termed. Thus in gravity batteries a crust of zinc sulphate often formed over the edge of the jar due to the solution creeping and evaporating. As a liquid withdraws from a surface which it does not wet, creeping as above is prevented by coating the edge with paraffin wax, something which water does not moisten. It also causes the liquids of a battery cell to reach the connections and injure them by oxidation. The solutions creep up in the pores of the carbons of a battery and oxidize the clamps. To give good connections a disc of platinum or of lead is used for the contact as not being attacked. Another way is to dip the upper ends of the dry and warm carbons into melted paraffin wax, or to apply the wax to the hot carbons at the top, and melt it in with a hot iron. 106 STANDARD ELECTRICAL DICTIONARY. Carbon. (a) One of the elements; atomic weight, 12. It exists in three allotropic modifications, charcoal, graphite and diamond. In the graphitic form it is used as an electric current conductor, as in batteries and for arc lamp, electrodes and incandescent lamp filaments. It is the only substance which conducts electricity and which cannot be melted with comparative ease by increase of current. (See Resistance.) (b) The carbon plate of a battery or rod of an arc lamp. To secure greater conductivity in lamp carbons, they are sometimes plated with nickel or with copper. (c) v. To place carbons in arc lamps. This has generally to be done once in twenty-four hours, unless the period of burning is very short. Carbon, Artificial. For lamps, carbons and battery plates carbons are made by igniting, while protected from the action of the air, a mixture of carbon dust and a cementing and carbonizable substance. Lamp black may be added also. Powdered coke or gas carbon is mixed with molasses, coal tar, syrup, or some similar carbonaceous liquid. It is moulded into shape. For lamp carbons the mixture is forced from a vessel through a round aperture or die, by heavy pressure, and is cut into suitable lengths. For battery plates it may be simply pressed into moulds. The carbons are ignited in covered vessels and also covered with charcoal dust, lamp black or its equivalent. They are heated to full redness for some hours. After removal and cooling they are sometimes dipped again into the liquid used for cementing and reignited. Great care in securing pure carbon is sometimes necessary, especially for lamps. Fine bituminous coal is sometimes used, originally by Robert Bunsen, in 1838 or 1840; purification by different processes has since been applied; carbon from destructive distillation of coal tar has been used. The famous Carré carbons are made, it is said, from 15 parts very pure coke dust, five parts calcined lamp-black, and seven or eight parts sugar--syrup mixed with a little gum. Five hours heating, with subsequent treatment with boiling caramel and reignition are applied. The latter treatment is termed "nourishing." Napoli used three parts of coke to one of tar. Sometimes a core of different carbon than the surrounding tube is employed. 107 STANDARD ELECTRICAL DICTIONARY. The following are the resistances of Carré's carbons per meter (39.37 inches): Diameter in Diameter in Resistance in Ohms. Millimeters. Inches. @ 20° C. (98° F.) 1 .039 50.000 2 .078 12.5 3 .117 5.55 4 .156 3.125 5 .195 2.000 6 .234 1.390 8 .312 .781 10 .390 .5 12 .468 .348 15 .585 .222 18 .702 .154 20 .780 .125 At high temperatures the resistance is about one-third these amounts. A layer of copper may increase the conductivity one hundred times and prolong the duration 14 per cent. Thus a layer of copper 1/695 millimeter (1/17300 inch) thick increases the conductivity 4.5 times; a coating 1/60 millimeter (1/1500 inch) thick increases the conductivity one hundred and eleven times. Carbon, Cored. A carbon for arc lamps with a central core of softer carbon than the exterior zone. It fixes the position of the arc, and is supposed to give a steadier light. Synonym--Concentric Carbon. Carbon Holders. In arc lamps, the fixed clamps for holding the ends of the carbons. Carbonization. The igniting in a closed vessel, protected from air, of an organic substance so as to expel from it all the constituents except part of the carbon; destructive distillation. (See Carbonized Cloth.) Carbonized Cloth. Cloth cut in discs and heated in vessels protected from the air, until reduced to carbon. The heating is sometimes conducted in vacuo. They are placed in a pile in a glass or other insulating tube, and offer a resistance which can be varied by pressure. The greater the pressure the less will be the resistance, and vice versa. Carbon Dioxide. A compound gas, CO2. It is composed of Carbon, 12 parts by weight. Oxygen. 32 " Specific gravity, 1.524 (Dulong and Berzelins). Molecular weight, 44. It is a dielectric of about the resistance of air. Its specific inductive capacity at atmospheric pressures is 1.000356 (Boltzmann). 1.0008 (Ayrton). Synonyms--Carbonic Acid--Carbonic Acid Gas. 108 STANDARD ELECTRICAL DICTIONARY Carbon, Volatilization of. In arc lamps the heat is so intense that it is believed that part of the carbon is volatilized as vapor before being burned or oxidized by the oxygen of the air. The same volatilization may take place in incandescent lamps which are overheated. Carcel. The standard of artificial illumination used in France. It is the light yielded by a standard lamp burning 42 grams (648 grains) of colza oil per hour, with a flame 40 millimeters (1.57 inch) in height. One carcel is equal to 9.5 to 9.6 candles. Carcel Lamp. The lamp giving the standard of illuminating power. The wick is cylindrical, giving an Argand or central draft flame. It is woven with 75 strands, and weighs 3.6 grams (55.5 grains) per decimeter (3.9 inches) of length. The chimney is 29 centimeters (11.3 inches) high, 47 millimeters (1.88 inch) in diameter at the bottom, contracting just above the wick to 34 millimeters (1.36 inch). Carcel Gas Jet. A standard Argand gas burner, made with proper rating to give the light of a definite number of carcels illuminating power. Cognizance must be taken of the quality of the gas as well as of the burner used. Carrying Capacity. In a current conductor, its capacity for carrying a current without becoming unduly heated. It is expressed in amperes. (See Wire Gauge, American.) Cascade. The arrangement of Leyden jars in series on insulating supports, as described below. Cascade, Charging and Discharging Leyden Jars In. An arrangement of Leyden jars in series for the purpose of charging and discharging. They are placed on insulating supports, the inner coating of one connected with the outer coating of the next one all through the series. The actual charge received by such a series, the outer coating of one end jar being grounded, and the inner coating of the other being connected to a source of high potential, or else the same being connected to electrodes of opposite potentials is no greater than that of a single jar, but a much higher potential difference can be developed without risk of perforating the glass of a jar. The difference of potential in each jar of the series is equal to the total potential difference divided by the number of jars. The energy of discharge is equal to the same fraction of the energy of a single jar charged with the same quantity. [Transcriber's note: The equal distribution of potential assumes all the jars have the same capacity. The charge on all jars is the same since they are in series.] 109 STANDARD ELECTRICAL DICTIONARY. Case-hardening, Electric. The conversion of the surface of iron into steel by applying a proper carbonaceous material to it while it is heated by an electric current. It is a superficial cementation process. Cataphoresis. Electric osmore; the transfer of substances in solution through porous membranes under the influence probably of electrolysis, but without themselves being decomposed. Cautery, Electric. An electro-surgical appliance for removing diseased parts, or arresting hemorrhages, taking the place of the knife or other cutting instrument. The cautery is a platinum wire heated to whiteness by an electric current, and when in that condition used to cut off tumors, stop the flow of blood and parallel operations. The application is painful, but by the use of anaesthetics pain is avoided, and the healing after the operation is greatly accelerated. The heated wire of the cautery can be used for cutting operations in many cases where excision by a knife would be almost impracticable. Synonyms--Galvano-cautery--Galvano-caustry--Galvano-electric, do.--Galvano-thermal, do. C. C. A contraction of cubic centimeter. It is often written in small letters, as 100 c.c., meaning 100 cubic centimeters. Cell, Constant. A cell which yields a constant and uniform current under unvarying conditions. This implies that neither the electro-motive force or the resistance of the cell shall vary, or else that as the electro-motive forces run down the resistance shall diminish in proper proportion to maintain a constant current. There is really no constant cell. The constancy is greatest when the external resistance is high in proportion to the internal resistance. Cell, Electrolytic. A vessel containing the electrolyte, a liquid decomposable by the current, and electrodes, arranged for the passage of a decomposing current. The voltameter, q. v., is an example. Cell, Standard Voltaic. A cell designed to be a standard of electro-motive force; one in which the same elements shall always be present under the same conditions, so as to develop the same electro-motive force. In use the circuit is closed only for a very short time, so that it shall not become altered by polarization or exhaustion. Cell, Standard Voltaic, Daniell's. A zinc-copper-copper sulphate couple. Many forms are used. Sometimes a number of pieces of blotting paper are interposed between two plates, one of copper--the other of zinc. The paper next the copper is soaked in copper sulphate solution, and those next the zinc in zinc sulphate solution, of course before being put together. Sometimes the ordinary porous cup combination is employed. The cut shows a modification due to Dr. Fleming (Phil. Mag. S. 5, vol. xx, p. 126), which explains itself. The U tube is 3/4-inch diameter, and 8 inches long. Starting with it empty the tap A is opened, and the whole U tube filled with zinc sulphate solution, and the tap A is closed. The zinc rod usually kept in the tube L is put in place, tightly corking up its end of the U tube. The cock C is opened, which lowers the level of the solution in the right-hand limb of the U tube only. The tap B is opened and the copper sulphate solution is run in, preserving the line of separation of the two solutions. The copper rod is taken out of its tube M, and is put in place. India rubber corks are used for both rods. As the liquids begin to mix the mixture can be drawn off at C and the sharp line of demarcation re-established. In Dr. Sloane's standard cell two test tubes are employed for the solutions and a syphon is used to connect them. Oxidation of the zinc lowers the E. M. F.; oxidation of the copper raises it. With solutions of equal sp. gr. the E. M. F. is 1.104 volts. If the copper sulphate solution is 1.100 sp. gr. and the zinc sulphate solution 1.400 sp. gr., both at 15° C. (59°F.), the E. M. F. will be 1.074 volt. Clean pure zinc and freshly electrolyzed copper should be used. Fig. 79 STANDARD DANIELL CELL--FLEMING'S FORM. 110 STANDARD ELECTRICAL DICTIONARY. Cell, Standard Voltaic, Latimer Clark's. A mercury and zinc electrode couple with mercurous sulphate as excitant and depolarizer. The positive element is an amalgam of zinc, the negative is pure mercury. Each element, in a representative form, the H form, is contained in a separate vessel which communicate by a tube. Over the pure mercury some mercurous sulphate is placed. Both vessels are filled to above the level of the connecting tube with zinc sulphate solution, and kept saturated. It is tightly closed or corked. The E. M. F. at 15° C (59° F.) is 1.438. Temperature correction (1 - (.00077 *(t - 15° C) ) ) t being expressed in degrees centigrade (Rayleigh). A diminution in specific gravity of the zinc solution increases the E. M. F. The cell polarizes rapidly and the temperature coefficient is considered too high. Fig. 80. LATIMER CLARK'S STANDARD CELL. 111 STANDARD ELECTRICAL DICTIONARY. Cements, Electrical. A few cements find their use in electrical work. Marine glue, Chatterton's compound, and sealing wax may be cited. Centi-. Employed as a prefix to indicate one-hundredth, as centimeter, the one-hundredth of a meter; centi-ampere, the one-hundredth of an ampere. Centigrade-scale. A thermometer scale in use by scientists of all countries and in general use in many. The temperature of melting ice is 0º; the temperature of condensing steam is 100° ; the degrees are all of equal length. To reduce to Fahrenheit degrees multiply by 9 and divide by 5, and add 32 algebraically, treating all readings below 0º as minus quantities. For its relations to the Reamur scale, see Reamur Scale. Its abbreviation is C., as 10º C., meaning ten degrees centigrade. Centimeter. A metric system unit of length; one-hundredth of a meter; 0.3937 inch. The absolute or c. g. s. unit of length. Centimeter-gram-second System. The accepted fundamental or absolute system of units, called the C. G. S. system. It embraces units of size, weight, time, in mechanics, physics, electricity and other branches. It is also called the absolute system of units. It admits of the formation of new units as required by increased scope or classification. The following are basic units of the system : Of length, centimeter; of mass, gram; of time, second: of force, dyne: of work or energy, erg. See Dyne, Erg., and other units in general. 112 STANDARD ELECTRICAL DICTIONARY. Central Station Distribution or Supply. The system of supplying electric energy in current form from a main generating plant to a district of a number of houses, factories, etc. It is in contrast with the isolated plant system in which each house or factory has its own separate generating installment, batteries or dynamos. Centre of Gravity. A point so situated with respect to any particular body, that the resultant of the parallel attracting forces between the earth and the several molecules of the body always passes through it. These are resultants of the relative moments of the molecules. If a body is suspended, as by a string, the centre of gravity always lies vertically under its point of suspension. By two trials the point of intersection of plumb lines from the point of suspension being determined the centre of gravity is known. The vertical from the point of support coincides with the line of direction. Centre of Gyration. The centre of gyration with respect to the axis of a rotating body is a point at which if the entire mass of the body were concentrated its moment of inertia would remain unchanged. The distance of this point from the axis is the radius of gyration. Centre of Oscillation. The point referred to in a body, suspended or mounted to swing like a pendulum, at which if all the mass were concentrated, 1t would complete its oscillations in the same time. The distance from the axis of support to this point gives the virtual length of the pendulum which the body represents. Centre of Percussion. The point in a suspended body, one free to swing like a pendulum, at which an impulse may be applied, perpendicular to the plane through the axis of the body and through the axis of support without shock to the axis. It is identical with the centre of oscillation, q. v., when such lies within the body. Centrifugal Force. The force which draws a body constrained to move in a curved path away from the centre of rotation. It is really due to a tangential impulse and by some physicists is called the centrifugal component of tangential velocity. It has to be provided against in generator and motor armatures, by winding them with wire or bands to prevent the coils of wire from spreading or leaving their bed upon the core. 113 STANDARD ELECTRICAL DICTIONARY. Centrifugal Governor. The usual type of steam-engine governor. The motion of the engine rotates a system of weights, which are forced outward by centrifugal force, and are drawn inwards by gravity or by springs. Moving outwards they shut off steam, and moving inwards they admit it, thus keeping the engine at approximately a constant speed. The connections between them and the steam supply and the general construction vary widely in different governors. C. G. S. Abbreviation or symbol for Centimeter-gram-second, as the C. G. S. system. (See Centimeter-gram-second System.) It is sometimes expressed in capitals, as above, and sometimes in small letters, as the c. g. s. unit of resistance. Chamber of Incandescent Lamp. The interior of the bulb of an incandescent lamp. (See Lamp, Incandescent.) Fig. 81. CHARACTERISTIC CURVE OF A DYNAMO. FIG. 82. DROOPING CHARACTERISTIC. Characteristic Curve. A curve indicating the variations in electro-motive force developed during the rotations of the armature of a dynamo or other generator of E. M. F. The term as used in the electrical sense is thus applied, although the indicator diagram of a steam engine may be termed its characteristic curve, and so in many other cases. As the amperes taken from a series generator are increased in number, the E. M. F. rises, it may be very rapidly up to a certain point, and thereafter more slowly. To construct the curve coordinates, q. v., are employed. The resistance of the dynamo and of the outer circuit being known, the current intensity is measured. To obtain variations in electro-motive force the external resistance is changed. Thus a number of ampere readings with varying known resistance are obtained, and for each one an electro-motive force is calculated by Ohm's law. From these data a curve is plotted, usually with volts laid off on the ordinate and amperes on the abscissa. By other methods other characteristic curves may be obtained, for which the titles under Curve may be consulted. 114 STANDARD ELECTRICAL DICTIONARY. Characteristic, Drooping. A characteristic curve of a dynamo which indicates a fall in voltage when an excessive current is taken from the dynamo in question. It is shown strongly in some Brush machines, and is partly due to the arrangements for cutting out two of the coils as they approach the neutral line. It is an advantage, as it protects from overheating on short circuit. Characteristic, External. In a dynamo the characteristic curve in which the relations of volts between terminals to amperes in the outer circuit are plotted. (See Curve, External Characteristic.) Characteristic, Internal. A characteristic curve of a shunt dynamo, in which the relations of volts to amperes in the shunt circuit is plotted. Characteristics of Sound. Of interest, electrically, as affecting the telephone, they comprise: (1) Pitch, due to frequency of vibrations. (2) Intensity or loudness, due to amplitude of waves of sound. (3) Quality or timbre, the distinguishing characteristics of any specific sound due to overtones, discords, etc., by which the sound is recognizable from others. The telephone is held by the U. S. courts to be capable of reproducing the voice by means of the undulatory current. (See Current, Undulatory.) Charge. The quantity of electricity that is present on the surface of a body or conductor. If no electricity is supplied, and the conductor is connected to the earth, it is quickly discharged. A charge is measured by the units of quantity, such as the coulomb. The charge that a conductor can retain at a given rise of potential gives its capacity, expressible in units of capacity, such as the farad. A charge implies the stretching or straining between the surface of the charged body, and some complimentary charged surface or surfaces, near or far, of large or small area, of even or uneven distribution. Charge. v. (a) To introduce an electrostatic charge, as to charge a condenser. (b) To decompose the elements of a secondary battery, q. v., so as to render it capable of producing a current. Thus, a spent battery is charged or recharged to enable it to do more work. Synonyms--Renovate--Revivify--Recharge. 115 STANDARD ELECTRICAL DICTIONARY. Charge, Bound. A charge of electricity borne by the surface of a body so situated with reference to another oppositely charged body, that the charge is imperceptible to ordinary test, will not affect an electroscope nor leave the surface if the latter is connected to the earth. To discharge such a body it must be connected to its complimentarily charged body. The bound charge was formerly called dissimulated or latent electricity. (See Charge, Free.) The charge or portion of a charge of a surface which is neutralized inductively by a neighboring charge of opposite kind. The degree of neutralization or of binding will depend on the distance of the two charged surfaces from one another and on the electro-static nature of the medium intervening, which must of necessity be a dielectric. A charge not so held or neutralized is termed a free charge. Thus a surface may be charged and by the approach of a surface less highly charged may have part of its charge bound. Then if connected to earth. it will part with its unbound or free charge, but will retain the other until the binding surface is removed, or until the electricity of such surface is itself bound, or discharged, or until connection is made between the two surfaces. Thus a body may have both a bound and a free charge at the same time. Charge, Density of. The relative quantity of electricity upon a given surface. Thus a charged surface may have an evenly distributed charge or one of even density, or an unevenly distributed charge or one of uneven density. In a thunderstorm the earth has a denser charge under the clouds than elsewhere. Synonym--Electrical Density. Charge, Dissipation of. As every body known conducts electricity, it is impossible so to insulate a surface that it will not lose its charge by leakage. An absolute vacuum might answer, and Crookes in a high vacuum has retained a charge against dissipation for years. The gradual loss is termed as above. Charge, Distribution of. The relation of densities of charge on different parts of a charged body. On a spherical conductor the charge is normally of even distribution; on other conductors it is unevenly distributed, being of greatest density at points, edges, and parts of smallest radius of curvature. Even distribution can also be disturbed by local induction, due to the presence of oppositely charged bodies. 116 STANDARD ELECTRICAL DICTIONARY. Charge, Free. The charge borne by an insulated body, independent of surrounding objects. Theoretically it is an impossibility. A charge always has its compliment somewhere in surrounding objects. As a matter of convenience and convention, where the complimentary charge is so distributed that its influence is not perceptible the charge is called a free charge. If connected to earth the free charge will leave the body. If the body is connected with an electroscope the free charge will affect the same. (See Charge, Bound.) Charge, Residual. When a Leyden jar or other condenser is discharged by the ordinary method, after a few minutes standing a second discharge of less amount can be obtained from it. This is due to what is known as the residual charge. It seems to be connected in some way with the mechanical or molecular distortion of the dielectric. The jarring of the dielectric after discharge favors the rapidity of the action, diminishing the time required for the appearance of the residual charge. The phenomenon, it will be seen, is analogous to residual magnetism. This charge is the reciprocal of electric absorption and depends for its amount upon the nature of the dielectric. (See Absorption, Electric, and Capacity, Residual.) Synonym--Electric Residue. Chatterton's Compound. A cement used for cementing together layers or sheets of gutta percha, and for similar purposes in splicing telegraph cables. Its formula is: Stockholm Tar, 1 part. Resin, 1 part. Gutta Percha, 3 parts. All parts by weight. Chemical Change. When bodies unite in the ratio of their chemical equivalents, so as to represent the satisfying of affinity or the setting free of thermal or other energy, which uniting is generally accompanied by sensible heat and often by light, as in the ignition of a match, burning of a candle, and, when the new compound exhibits new properties distinct from those of its components, a chemical combination is indicated. More definitely it is a change of relation of the atoms. Another form of chemical change is decomposition, the reverse of combination, and requiring or absorbing energy and producing several bodies of properties distinct from those of the original compound. Thus in a voltaic battery chemical combination and decomposition take place, with evolution of electric instead of thermal energy. Chemical Equivalent. The quotient obtained by dividing the atomic weight, q. v., of an element by its valency, q. v. Thus the atomic weight of oxygen is 16, its valency is 2. its chemical equivalent is 8. It is the weight of the element corresponding to a unit weight of hydrogen, either as replacing it, or combining with it. In electro-chemical calculations the chemical equivalent is often conveniently used to avoid the necessity of dividing by the valency when atomic weights are used. The latter is really the better practice. The atomic weights in the old system of chemical nomenclature were chemical equivalents. 117 STANDARD ELECTRICAL DICTIONARY. Chemical Recorder. A form of telegraphic recorder in which the characters, often of the Morse alphabet or some similar one, are inscribed on chemically prepared paper by decomposition affecting the compound with which the paper is charged. In the original chemical recorder of Bain, the instrument was somewhat similar to the Morse recorder, except that the motionless stylus, S, always pressing against the paper was incapable of making any mark, but being of iron, and the paper strip being impregnated with potassium ferrocyanide, on the passage of a current a stain of Prussian blue was produced where the stylus touched the paper. The current passes from the line by way of the iron stylus, through the paper, and by way of a brass surface, M, against which the paper is held and is pressed by the stylus, to the earth. This recorder is extremely simple and has no part to be moved by the current. The solution in which the paper is dipped contains a mixture of potassium ferrocyanide and ammonium nitrate. The object of the latter is to keep the paper moist. In recent recorders a solution of potassium iodide has been used, which gives a brown stain of free iodine, when the current passes. This stain disappears in a few days. Fig. 83. BAIN'S TELEGRAPH EMPLOYING CHEMICAL RECORDER. In the cut, R is the roll of paper, B is a tank of solution with roll, W1, for moistening the paper; M is the brass surface against which the stylus, S, presses the paper, P P; W, W are feed rollers; T is the transmitting key, and zk the battery; Pl, Pl are earth plates. The apparatus is shown duplicated for each end. 118 STANDARD ELECTRICAL DICTIONARY. Chemistry. The science treating of atomic and molecular relations of the elements and of chemical compounds of the same. Chimes, Electric. An apparatus employed to illustrate the principles of the electrostatic charge, involving the ringing of bells by electrostatic attraction and repulsion. It is used in connection with a frictional, or influence electric machine. Two bells are employed with a button or clapper suspended between them. One bell is connected to one of the prime conductors, q. v., of the machine. The other insulated therefrom is connected to earth, or if an influence machine is used, to the other prime conductor. The clappers are hung by a silk thread, so as to be entirely insulated. On working the machine the bells become oppositely excited. A clapper is attracted to one, then when charged is repelled and attracted to the other, it gives up its charge and becoming charged with similar electricity to that of the bell it touches, is repelled and attracted to the other, and this action is kept up as long as the excitement continues, the bells ringing continuously. Fig. 84. ELECTRIC CHIMES. Chronograph, Electric. An apparatus for indicating electrically, and thereby measuring, the lapse of time. The periods measured may be exceedingly short, such as the time a photographic shutter takes to close, the time required by a projectile to go a certain distance, and similar periods. A drum rotated with even and known velocity may be marked by a stylus pressed upon it by the action of an electro-magnet when a key is touched, or other disturbance. Then the space between two marks would give the period elapsing between the two disturbances of the circuit. As it is practically impossible to secure even rotation of a drum, it is necessary to constantly measure its rate of rotation. This is effected by causing a tuning-fork of known rate of vibration to be maintained in vibration electrically. A fine point or bristle attached to one of its arms, marks a sinuous line upon the smoked surface of the cylinder. This gives the basis for most accurately determining the smallest intervals. Each wave drawn by the fork corresponds to a known fraction of a second. For projectiles, the cutting of a wire opens a circuit, and the opening is recorded instead of the closing. By firing so as to cut two wires at a known distance apart the rate is obtained by the chronograph. Synonym--Chronoscope. 119 STANDARD ELECTRICAL DICTIONARY. Chutaux's Solution. A solution for bichromate batteries. It is composed as follows: Water, 1,500 parts Potassium bichromate, 100 parts mercury bisulphate, 100 parts 66° sulphuric acid, 50 parts. Circle, Galvanic or Voltaic. A term for the voltaic circuit; obsolete. Fig. 85. MAGIC CIRCLE. Circle, Magic. A form of electro-magnet. It is a thick circle of round iron and is used in connection with a magnetizing coil, as shown, to illustrate electro-magnetic attraction. 120 STANDARD ELECTRICAL DICTIONARY. Circuit. A conducting path for electric currents properly forming a complete path with ends joined and including generally a generating device of some kind. Part of the conduction may be true and part electrolytic. (See Electrolytic Conduction.) The term has become extended, so that the term is often applied to any portion of a circuit conveniently considered by itself. The simplest example of a complete circuit would be a circular conductor. If rotated in the earth's field so as to cut its lines of force a current would go through it, and it would be an electric circuit. Another example is a galvanic battery with its ends connected by a wire. Here the battery generates the current which, by electrolytic conduction, goes through the battery and by true conduction through the wire. For an example of a portion of a circuit spoken of as "a circuit" see Circuit, Astatic. Circuit, Astatic. A circuit so wound with reference to the direction of the currents passing through it that the terrestrial or other lines of force have no directive effect upon it, one member counteracting the other. It may be produced by making the wire lie in two closed curves, A and B, each enclosing an equal area, one of identical shape and disposition with the other, and with the current circulating in opposite directions in each one. Thus each circuit represents a magnetizing turn of opposite polarity and counteracting each other's directive tendency exhibited in a field of force with reference to an axis a c. Another form of astatic circuit is shown in Fig. 86. The portions C, D, lying on opposite sides of the axis of rotation a c, are oppositely acted on by the earth's directive force as regards the direction of their rotation. Figs. 86 and 87. ASTATIC CIRCUITS. Circuit, Branch. A circuit dividing into two or more parts in parallel with each other. 121 STANDARD ELECTRICAL DICTIONARY. Circuit Breaker. Any apparatus for opening and closing a circuit is thus termed, but it is generally applied to automatic apparatus. A typical circuit breaker is the hammer and anvil of the induction coil. (See Induction Coil; Anvil.) Again a pendulum connected to one terminal of a circuit may swing so as to carry a point on its lower end through a globule of mercury as it swings, which globule is connected to the other terminal. A great many arrangements of this character have been devised. Synonym.--Contact Breaker. Circuit Breaker, Automatic. A circuit breaker worked by the apparatus to which it is attached, or otherwise automatically. (See Induction Coil; Anvil; Bell, Electric.) Circuit Breaker, File. A coarsely cut file, forms one terminal of an electric circuit, with a straight piece of copper or steel for the other terminal. The latter terminal drawn along the teeth makes and breaks the contact once for every tooth. The movable piece should have an insulated handle. Circuit Breaker, Mercury. A circuit breaker which may be identical in principle, with the automatic circuit breaker of an induction coil, but in which in place of the anvil, q. v., a mercury cup is used, into which the end of a wire dips and emerges as it is actuated by the impulses of the current. Each dip makes the contact, which is broken as the wire springs back. The mercury should be covered with alcohol to protect it from oxidation. Circuit Breaker, Pendulum. A circuit breaker in which a pendulum in its swing makes and breaks a contact. It may be kept in motion by clockwork, or by an electro-magnet, attracting intermittently an armature attached to its rod, the magnet circuit being opened and closed by the pendulum or circuit breaker itself. A mercury contact may be used with it. Fig. 88. PENDULUM CIRCUIT BREAKER. 122 STANDARD ELECTRICAL DICTIONARY. Circuit Breaker, Tuning Fork. A circuit breaker in which a tuning fork makes and breaks the circuit. Each vibration of one of the prongs in one direction makes a contact, and the reverse vibration breaks a contact. The adjustment is necessarily delicate, owing to the limited amplitude of the motion of the fork. The fork is kept in vibration sometimes by an electro-magnet, which is excited as the circuit is closed by the fork. One leg of the fork acts as the armature of the magnet, and is attracted according to its own natural period. Circuit Breaker, Wheel. A toothed wheel with a spring bearing against its teeth. One terminal of a circuit connects with the wheel through its axle, the other connects with the spring. When the wheel is turned the circuit is opened and closed once for each tooth. The interstices between teeth on such a wheel may be filled with insulating material, giving a cylindrical surface for the contact spring to rub on. Fig. 89--TOOTHED WHEEL CIRCUIT BREAKER. Circuit, Closed. A circuit whose electric continuity is complete; to make an open circuit complete by closing a switch or otherwise is to close, complete, or make a circuit. Synonyms--Completed Circuit--Made Circuit. Circuit, Compound. A circuit characterized by compounding of generating or receiving devices, as including several separate batteries, or several motors, or other receiving devices. It is sometimes used to indicate a circuit having its battery arranged in series. It should be restricted to the first definition. 123 STANDARD ELECTRICAL DICTIONARY. Circuit, Derived. A partial circuit connected to two points of another circuit, so as to be in parallel with the portion thereof between such two points; a shunt circuit. Synonyms--Shunt Circuit--Derivative Circuit--Parallel Circuit. Circuit, Electric, Active. A circuit through which a current passes. The circuit itself need only be a conducting ring, or endless wire. Generally it includes, as part of the circuit, a generator of electro-motive force, and through which generator by conduction, ordinary or electrolytic, the same current goes that passes through the rest of the circuit. One and the same current passes through all parts of a series circuit when such current is constant. A current being produced by electro-motive force, and electromotive force disappearing in its production in an active circuit, there must be some source of energy which will maintain electromotive force against the drain made upon it by the current. The simplest conception of an active electric circuit is a ring or endless conductor swept through a field of force so as to cut lines of force. A simple ring dropped over a magnet pole represents the simplification of this process. In such a ring a current, exceedingly slight, of course, will be produced. In this case there is no generator in the circuit. An earth coil (see Coil, Earth,) represents such a circuit, with the addition, when experimented with, of a galvanometer in the circuit. In practice, a circuit includes a generator such as a battery or dynamo, and by conductors is led through a continuous path. Electric lamps, electrolytic cells, motors and the like may be included in it. The term "circuit" is also applied to portions of a true circuit, as the internal circuit, or external circuit. A certain amount of elasticity is allowed in its use. It by no means necessarily indicates a complete through circuit. Circuit, Electrostatic. (a) A circuit through which an electrostatic or high tension discharge takes place. It is virtually an electric circuit. (b) The term is applied also to the closed paths of electrostatic lines of force. Circuit, External. The portion of a circuit not included within the generator. Circuit, Grounded. A circuit, one of whose members, the return circuit, is represented by the earth, so that the earth completes the circuit. In telegraphy each end of the line is grounded or connected to an earth-plate, q. v., or to the water or gas-pipes, and the current is assumed to go through the earth on its return. It really amounts to a discharging at one end, and charging at the other end of the line. The resistance of the earth is zero, but the resistance of the grounding or connection with the earth may be considerable. Synonyms--Ground Circuit--Earth Circuit--Single Wire Circuit. [Transcriber's note: The resistance of the earth is high enough that large power system return currents may produce dangerous voltage gradients when a power line is shorted to the ground. Don't walk near downed lines!] 124 STANDARD ELECTRICAL DICTIONARY. Circuit Indicator. A pocket compass, decomposition apparatus, galvanometer or other device for indicating the condition of a wire, whether carrying a current or not, and, if carrying one, its direction, and sometimes roughly indicating its strength. Circuit, Internal. The portion of an electric circuit included within the generator. Circuit, Line. The portion of a circuit embracing the main line or conductor, as in a telegraph circuit the line carried on the poles; distinguished from the local circuit (see Circuit, Local,) in telegraphy. Circuit, Local. In telegraphy, a short circuit with local generator or battery included, contained within the limits of the office or station and operated by a relay, q. v. This was the original local circuit; the term is applicable to any similar arrangement in other systems. Referring to the cut, the main line circuit includes the main battery, E, Key, P, Relay, R, ground plates, G, G1. The relay magnet opens and closes the local circuit with its local battery, L, and sounder magnet, H, with its armature, B. The minor parts, such as switches, are omitted. Fig. 90. LOCAL CIRCUIT OF TELEGRAPH SYSTEM. Circuit, Local Battery. A local circuit worked by and including a local battery in its course. 125 STANDARD ELECTRICAL DICTIONARY. Circuit, Loop. A minor circuit introduced in series into another circuit by a cut-out, or other device, so as to become a portion of the main circuit. Circuit Loop Break. A supporter or bracket with two arms for carrying insulators. Its use is to enable a loop connection to be introduced into a line which is cut, so as to enable the connection of the ends of the loop to be made, one to each end of the through wire, which ends are attached, one to each of the two insulators. Circuit, Main. The circuit including the main line and apparatus supplied by the main battery, as distinguished from the local circuit. (See Circuit, Local.) Circuit, Main Battery. The main circuit, including the main or principal battery in its course. Circuit, Metallic. A circuit in which the current outside the generator, or similar parts, is carried on a metallic conductor; a circuit without any ground circuit. The including of a galvanic battery or electro plating bath would not prevent the application of the term; its essential meaning is the omission of the earth as the return circuit. Circuit, Negative Side of. The side of a circuit opposite to the positive side. (See Circuit, Positive Side of) It is defined as the half of a circuit leading to the positive terminal of the generator. Circuit, Open. A circuit with its continuity broken, as by disconnecting a wire from the battery, or opening a switch; a broken circuit is its synonym. To open a switch or disconnect or cut the wire is termed opening or breaking the circuit. Synonyms--Incomplete Circuit--Broken Circuit. Circuit, Positive Side of. This side is such that an observer standing girdled by the current with his head in the positive side or region, would see the current pass around him from his right toward his left hand. It is also defined as the half of the circuit leading to the negative terminal of the generator. Circuit, Recoil. The portion of a parallel circuit presenting an alternative path, q. v., for a disruptive discharge. Circuit, Return. (a) The part of a circuit extending from the generator to the extreme point in general, upon which no apparatus is placed. In telegraph systems the ground generally forms the return circuit. The distinction of return and working circuit cannot always be made. (b) It may also be defined as the portion of a circuit leading to the negative terminal of the generator. 126 STANDARD ELECTRICAL DICTIONARY Circuits, Forked. Circuits starting in different paths or directions from one and the same point. Circuit, Simple. A circuit containing a single generator, and single receiver of any kind, such as a motor or sounder, with a single connecting conductor. It is also used to indicate arrangement in multiple arc, but not generally, or with approval. Circuits, Parallel. Two or more conductors starting from a common point and ending at another common point are termed, parallel circuits, although really but parts of circuits. If of equal resistance their joint resistance is obtained by dividing the resistance of one by the number of parallel circuits. If of unequal resistance r, r', r" , etc., the formula for joint resistance, R, of two is R = ( r * r' ) / ( r + r' ) This resistance may then be combined with a third one by the same formula, and thus any number may be calculated. Synonym--Shunt Circuit. Circuit, Voltaic. Properly a circuit including a conductor and voltaic couple. It is also applied to the electric circuit, q. v., or to any circuit considered as a bearer of current electricity. Circular Units. Units of area, usually applied to cross sectional area of conductors, by whose use area is expressed in terms of circle of unit diameter, usually a circular mil, which is the area of a circle of one-thousandth of an inch diameter, or a circular millimeter, which is the area of a circle of one millimeter diameter. Thus a wire one-quarter of an inch in diameter has an area of 250 circular mils; a bar one centimeter in diameter has an area of ten circular millimeters. [Transcriber's Note: Area is the diameter squared. A 1/4 inch wire has 62500 circular mils of area. A one centimeter (10 millimeter) wire has 100 circular millimeters of area. Actual area = circular mils * (PI/4).] Circumflux. The product of the total number of conductor turns on the armature of a dynamo or motor, into the current carried thereby. For two pole machines it is equal to twice the armature ampere-turns; for four pole machines to four times such quantity, and so on. Clamp. The appliance for grasping and retaining the end of the rod that holds a carbon in the arc lamp. Clark's Compound. A cement used for the outside of the sheath of telegraph cables. Its formula is: Mineral Pitch, 65 parts. Silica, 30 parts. Tar, 5 parts. All parts by weight. 127 STANDARD ELECTRICAL DICTIONARY. Cleats. A support; a short block of wood, grooved transversely, for holding electric wires against a wall. For the three wire system three grooves are used. The entire wiring of apartments is sometimes done by the "cleat system," using cleats instead of battens, q. v., or mouldings. The cleats are secured against the wall with the grooves facing it, and the wires are introduced therein. Fig. 91. TWO WIRE CLEAT. Fig. 92. THREE WIRE CLEAT. Cleat, Crossing. A cleat with grooves or apertures to support wires which cross each other. Two or three grooves are transverse, and on the under side, as above; one groove is longitudinal and on the upper side. Cleavage, Electrification by. If a mass of mica is rapidly split in the dark a slight flash is perceived. Becquerel found that in such separation the two pieces came away oppositely charged with electricity. The splitting of mica is its cleavage. Clock, Controlled. In a system of electric clocks, the clocks whose movements are controlled by the current, regulated by the master or controlling clock. Synonym--Secondary Clock. Clock, Controlling. In a system of electric clocks the master clock which controls the movements of the others, by regulating the current. Synonym--Master Clock. Clock, Electric Annunciator. A clock operating any form of electric annunciator, as dropping shutters, ringing bells, and the like. It operates by the machinery closing circuits as required at any desired hour or intervals. 128 STANDARD ELECTRICAL DICTIONARY. Clock, Electrolytic. A clock worked by the electrolytic deposition and resolution of a deposit of metal upon a disc. It is the invention of Nikola Tesla. A metallic disc is mounted on a transverse axis, so as to readily rotate. It is immersed in a vessel of copper sulphate. A current is passed through the bath, the terminals or electrodes being near to and facing the opposite edges of the disc, so that the line connecting the electrodes lies in the plane of the disc. If a current is passed through the solution by the electrodes, copper is deposited on one side of the disc, and as it rotates under the influence of the weight thus accumulated on one side, the same metal as it is brought to the other side of the disc is redissolved. Thus a continuous rotation is maintained. The cause of the deposition and solution is the position of the disc; one-half becomes negative and the other positive in their mutual relations. Clock, Self-winding Electric. A clock which is wound periodically by an electric motor and battery. Clockwork, Feed. In arc-lamps the system of feeding the carbon or carbons by clockwork whose movements are controlled by the resistance of the arc. This system is employed in the Serrin, and in the Gramme regulators, among others. The carbons, if they approach, move clockwork. The movement of this is stopped or freed by an electro-magnet placed in shunt around the arc and carbons. Cloisons. Partitions or divisions; applied to the winding of electro-magnets and coils where the winding is put on to the full depth, over single sections of the core, one section at a time, until the whole core is filled up. Closure. The closing or completion of a circuit by depressing a key or moving a switch. Clutch. In arc lamps a device for the feed of the upper carbons. In its simplest form it is simply a plate or bar pierced with a hole through which the carbon passes loosely. The action of the mechanism raises or lowers one end of the plate or bar. As it rises it binds and clutches the carbon, and if the action continues it lifts it a little. When the same end is lowered the carbon and clutch descend together until the opposite end of the clutch being prevented from further descent, the clutch approaches the horizontal position and the rod drops bodily through the aperture. The cut shows the clutches of the Brush double carbon lamp. In practice the lifting and releasing as regulated by an electro-magnet are so very slight that practically an almost absolutely steady feed is secured. A similar clutch is used in the Weston lamp. 129 STANDARD ELECTRICAL DICTIONARY. Clutch, Electro-magnetic. A clutch or appliance for connecting a shaft to a source of rotary motion while the latter is in action. In one form a disc, in whose face a groove has been formed, which groove is filled with a coil of wire, is attached to the loose wheel, while the shaft carries a flat plate to act as armature. On turning on the current the flat plate is attached, adheres, and causes its wheel to partake of the motion of the shaft. Contact is made by brushes and collecting rings. In the cut, A A is the attracted disc; the brushes, B B, take current to the collecting rings, C. The magnetizing coil is embedded in the body of the pulley, as shown. Fig. 93. CLUTCH OF BRUSH LAMP. Fig. 94. ELECTRO-MAGNETIC CLUTCH. 130 STANDARD ELECTRICAL DICTIONARY. Coatings of a Condenser or Prime Conductor. The thin conducting coatings of tinfoil, gold leaf or other conducting substance, enabling the surface to receive and part with the electric charge readily. Without such a coating the charge and discharge would be very slow, and would operate by degrees only, as one part of a non-conducting surface might be densely charged and another part be quite devoid of sensible charge. Code, Cipher. A code of arbitrary words to designate prearranged or predetermined words, figures or sentences. The systems used in commerce have single words to represent whole sentences or a number of words of a sentence. This not only imparts a degree of secrecy, but makes the messages much shorter. Codes are used a great deal in cable transmission. Code, Telegraphic. A telegraphic alphabet. (See Alphabets, Telegraphic.) Coefficient. In algebra, the numerical multiplier of a symbol, as in the expression "5x," 5 is the coefficient. In physics, generally a number expressing the ratio or relation between quantities, one of which is often unity, as a standard or base of the set of coefficients. Thus the coefficient of expansion by heat of any substance is obtained by dividing its volume for a given degree of temperature by its volume at the standard temperature as 0º C., or 32º F. This gives a fraction by which if any volume of a substance, taken at 0º C., or at whatever may be taken as the basic temperature, is multiplied, the expanded volume for the given change of temperature will be obtained as the product. A coefficient always in some form implies the idea of a multiplier. Thus the coefficient of an inch referred to a foot would be 1/12 or .833+, because any number of inches multiplied by that fraction would give the corresponding number of feet. [Transcriber's note: 1/12 is 0.0833+] Coefficient, Economic. In machinery, electric generators, prime motors and similar structures, the number expressing the ratio between energy absorbed by the device, and useful, not necessarily available, work obtained from it. It is equal to work obtained divided by energy absorbed, and is necessarily a fraction. If it exceeded unity the doctrine of the conservation of energy would not be true. The economic coefficient expresses the efficiency, q. v., of any machine, and of efficiencies there are several kinds, to express any one of which the economic coefficient may be used. Thus, let W--energy absorbed, and w = work produced ; then w/W is the economic coefficient, and for each case would be expressed numerically. (See Efficiency, Commercial--Efficiency, Electrical--Efficiency of Conversion.) The distinction between useful and available work in a dynamo is as follows: The useful work would include the work expended by the field, and the work taken from the armature by the belt or other mechanical connection. Only the latter would be the available work. 131 STANDARD ELECTRICAL DICTIONARY. Coercive or Coercitive Force. The property of steel or hard iron, in virtue of which it slowly takes up or parts with magnetic force, is thus termed ("traditionally"; Daniell). It seems to have to do with the positions of the molecules, as jarring a bar of steel facilitates its magnetization or accelerates its parting, when not in a magnetic field, with its permanent or residual magnetism. For this reason a permanent magnet should never be jarred, and permitting the armature to be suddenly attracted and to strike against it with a jar injures its attracting power. Coercive force is defined also as the amount of negative magnetizing force required to reduce remnant magnetism to zero. By some authorities the term is entirely rejected, as the phenomenon does not seem directly a manifestation of force. Coil and Coil Plunger. A device resembling the coil and plunge, q. v., except that for the plunger of iron there is substituted a coil of wire of such diameter as to enter the axial aperture of the other, and wound or excited in the same or in the opposite sense, according to whether attraction or repulsion is desired. Coil and Plunger. A coil provided with a core which is free to enter or leave the central aperture. When the coil is excited, the core is drawn into it. Various forms of this device have been used in arc lamp regulators. Synonym--Sucking coil. Fig. 95. COIL AND COIL PLUNGER OF MENGIES ARC LAMP. Fig. 96. COIL AND PLUNGER EXPERIMENT. 132 STANDARD ELECTRICAL DICTIONARY. Coil and Plunger, Differential. An arrangement of coil and plunger in which two plungers or one plunger are acted on by two coils, wound so as to act oppositely or differentially on the plunger or plungers. Thus one coil may be in parallel with the other, and the action on the plunger will then depend on the relative currents passing through the coils. Coil, Choking. A coil of high self-induction, used to resist the intensity of or "choke" alternating currents. Any coil of insulated wire wound around upon a laminated or divided iron core forms a choking coil. The iron coil is usually so shaped as to afford a closed magnetic circuit. A converter or transformer acts as a choking coil as long as its secondary is left open. In alternating current work special choking coils are used. Thus for theatrical work, a choking coil with a movable iron core is used to change the intensity of the lights. It is in circuit with the lamp leads. By thrusting in the core the self-induction is increased and the current diminishes, lowering the lamps; by withdrawing it the self-induction diminishes, and the current increases. Thus the lamps can be made to gradually vary in illuminating power like gas lights, when turned up or down. Synonyms--Kicking Coil--Reaction Coil. Fig. 97. DIFFERENTIAL COILS AND PLUNGERS. Fig. 98. BISECTED COILS. 133 STANDARD ELECTRICAL DICTIONARY. Coils, Bisected. Resistance coils with connections at their centers, as shown in the diagram. They are used for comparing the resistances of two conductors. The connections are arranged as shown in the coil, each coil being bisected. For the wires, movable knife-edge contacts are employed. The principle of the Wheatstone bridge is used in the method and calculations. Coil, Earth. A coil of wire mounted with commutator to be rotated so as to cut the lines of force of the earth's magnetic field, thereby generating potential difference. The axis of rotation may be horizontal, when the potential will be due to the vertical component of the earth's field, or the axis may be horizontal, when the potential will be due to the vertical component, or it may be set at an intermediate angle. Synonym--Delezenne's Circle. Fig. 99. DELEZENNE'S CIRCLE OR EARTH COIL. Coil, Electric. A coil of wire used to establish a magnetic field by passing a current through it. The wire is either insulated, or so spaced that its convolutions do not touch. Coil, Flat. A coil whose windings all lie in one plane, making a sort of disc, or an incomplete or perforated disc. Coil, Induction. A coil in which by mutual induction the electromotive force of a portion of a circuit is made to produce higher or lower electro-motive force, in an adjoining circuit, or in a circuit, part of which adjoins the original circuit, or adjoins part of it. An induction coil comprises three principal parts, the core, the primary coil and the secondary coil. If it is to be operated by a steady current, means must be provided for varying it or opening and closing the primary circuit. A typical coil will be described. 134 STANDARD ELECTRICAL DICTIONARY. The core is a mass of soft iron preferably divided to prevent extensive Foucault currents. A cylindrical bundle of soft iron wires is generally used. Upon this the primary coil of reasonably heavy wire, and of one or two layers in depth, is wrapped, all being carefully insulated with shellac and paper where necessary. The secondary coil is wrapped upon or over the primary. It consists of very fine wire; No. 30 to 36 is about the ordinary range. A great many turns of this are made. In general terms the electro-motive force developed by the secondary stands to that of the primary terminals in the ratio of the windings. This is only approximate. The greatest care is required in the insulating. The secondary is sometimes wound in sections so as to keep those parts differing greatly in potential far from each other. This prevents sparking, which would destroy the insulation. A make and break, often of the hammer and anvil type, is operated by the coil. (See Circuit Breaker, Automatic.) As the current passes through the primary it magnetizes the core. This attracts a little hammer which normally resting on an anvil completes the circuit. The hammer as attracted is lifted from the anvil and breaks the circuit. The soft iron core at once parts with its magnetism and the hammer falls upon the anvil again completing the circuit. This operation goes on rapidly, the circuit being opened and closed in quick succession. Every closing of the primary circuit tends to produce a reverse current in the secondary, and every opening of the primary circuit tends to produce a direct current in the secondary. Both are of extremely short duration, and the potential difference of the two terminals of the secondary may be very high if there are many times more turns in the secondary than in the primary. The extra currents interfere with the action of an induction coil. To avoid their interference a condenser is used. This consists of two series of sheets of tin foil. Leaves of paper alternate with the sheets of tin-foil, the whole being built up into a little book. Each sheet of tin-foil connects electrically with the sheet next but one to it. Thus each leaf of a set is in connection with all others of the same set, but is insulated from the others. One set of leaves of tin-foil connects with the hammer, the other with the anvil. In large coils there may be 75 square feet of tin-foil in the condenser. The action of the condenser is to dispose of the direct extra current. When the primary circuit is opened this current passes into the condenser, which at once discharges itself in the other direction through the coil. This demagnetizes the core, and the action intensifies and shortens the induced current. The condenser prevents sparking, and in general improves the action of the coil. Many details enter into the construction of coils, and many variations in their construction obtain. Thus a mercury cup into which a plunger dips often replaces the anvil and hammer. 135 STANDARD ELECTRICAL DICTIONARY. The induction coil produces a rapid succession of sparks, which may spring across an interval of forty inches. The secondary generally ends in special terminals or electrodes between which the sparking takes place. A plate of glass, two inches in thickness, can be pierced by them. In the great Spottiswoode coil there are 280 miles of wire in the secondary, and the wire is about No. 36 A.W.G. Fig. 100. VERTICAL SECTION OF INDUCTION COIL. Fig. l01. PLAN OF INDUCTION COIL CONNECTIONS. Induction coils have quite extended use in electrical work. They are used in telephone transmitters, their primary being in circuit with the microphone, and their secondary with the line and receiving telephone. In electric welding, and in the alternating current system they have extended application. In all these cases they have no automatic circuit breaker, the actuating current being of intermittent or alternating type. 136 STANDARD ELECTRICAL DICTIONARY. In the cuts the general construction of an induction coil is shown. In the sectional elevation, Fig. 100, A, is the iron core; B is the primary of coarse wire; C is a separating tube, which may be of pasteboard; D is the secondary of fine wire; E, E are the binding posts connected to the secondary; H, H are the heads or standards; K, K are the terminals of the primary; F is the vibrating contact spring; G, a standard carrying the contact screw; J is the condenser with wires, L, M, leading to it. Referring to the plan, Fig. 101, H represents the primary coil; B and A are two of the separate sheets of the condenser, each sheet with projecting ears; G, G are the heads of the coil; the dark lines are connections to the condenser. One set of sheets connects with the primary coil at C, and also with the vibrating spring shown in plan and in the elevation at F. The other set of sheets connects with the post, carrying the contact screw. The other terminal of the primary runs to a binding post E. F, in the plan is a binding post in connection with the standard and contact screw. Coil, Induction, Inverted. An induction coil arranged to have a lower electro-motive force in the secondary than in the primary. This is effected by having more convolutions in the primary wire than in the secondary. Such coils in practice are used with the alternating current and then do not include a circuit breaker or condenser. They are employed in alternating current system and in electric welding. (See Welding, Electric--Converter.) In the cut an inverted coil, as constructed for electric welding is shown. In it the primary coil is marked P; the secondary, merely a bar of metal, is marked E, with terminals S, S; the heavy coils, I, of iron wire are the core; K is a screw for regulating the clamps; J, Z is a second one for the same purpose, while between D and D' the heat is produced for welding the bars, B, B', held in the clamps, C, C'. It will be seen how great may be the difference in turns between the single circle of heavy copper rod or bar which is the secondary of the coil, and the long coil of wire forming the primary. Fig. 102. INVERTED INDUCTION COIL FOR ELECTRIC WELDING. 137 STANDARD ELECTRICAL DICTIONARY. Coil, Induction, Telephone. An induction coil used in telephone circuits. It is placed in the box or case near the transmitter. The primary is in circuit with the microphone. The secondary is in circuit with the line and receiving telephone. In the Bell telephone apparatus the primary of the induction coil is wound with No. 18 to 24 A. W. G. wire to a resistance of 1/2 ohm; the secondary, with No. 36 wire to a resistance of 80 ohms. The Edison telephone induction coil was wound with similar wires to a resistance of 3 to 4 ohms and of 250 ohms respectively. Coil, Magnetizing. A coil of insulated wire for making magnets; and for experimental uses; it has a short axis and central aperture of as small size as consistent with the diameter of the bar to be magnetized, which has to pass through it readily. The wire may be quite heavy, 2 or 3 millimeters (.08--.12 inch) thick, and is cemented together with carpenter's glue, or with shellac or ethereal solution of gum copal. In use it is passed over the bar a few times while a heavy current is going through it. It is used for magic circles also. (See Circle, Magic.) Fig. 103. MAGNETIZING COIL. Coil, Resistance. A coil constructed for the purpose of offering a certain resistance to a steady current. This resistance may be for the purpose of carrying out quantitative tests, as in Wheatstone bridge work (see Wheatstone's Bridge), or simply to reduce the intensity of a current. For the first class of work the coils are wound so as to prevent the creation of a magnetic field. This is effected by first doubling the wire without breaking it, and then starting at the bend the doubled wire, which is insulated, is wound on a bobbin or otherwise until a proper resistance is shown by actual measurement. The coils are generally contained or set in closed boxes with ebonite tops. Blocks of brass are placed on the top, and one end from one coil and one end from the next connect with the same block. By inserting a plug, P, so as to connect any two blocks, which have grooves reamed out for the purpose, the coil beneath will be short circuited. German silver, platinoid or other alloy, q. v., is generally the material of the wire. A great object is to have a wire whose resistance will be unaffected by heat. 138 STANDARD ELECTRICAL DICTIONARY. Fig. 104. RESISTANCE COILS AND CONNECTIONS, SHOWING PLUG. Coil, Rhumkorff. The ordinary induction coil with circuit breaker, for use with original direct and constant current, is thus termed. (See Coil, Induction.) Synonym--Inductorium. Coil, Ribbon. A coil made of copper ribbon wound flatwise, often into a disc-like shape, and insulated by tape or strips of other material intervening between the successive turns. Coils, Compensating. Extra coils on the field magnets of dynamos or motors, which coils are in series with the armature windings for the purpose of keeping the voltage constant. In compound wound machines the regular series-wound coil is thus termed. In a separately excited dynamo a coil of the same kind in circuit with the armature may be used as a compensator. Coils, Henry's. An apparatus used in repeating a classic experiment in electro-magnetic induction, due to Prof. Henry. It consists in a number of coils, the first and last ones single, the intermediate ones connected in pairs, and one of one pair placed on the top of one of the next pair. On opening or closing the circuit of an end coil the induced effect goes through the series and is felt in the circuit of the other end coil. Prof. Henry extended the series so as to include seven successive inductions, sometimes called inductions of the first, second, third and other orders. Frequently ribbon coils (see Coil, Ribbon,) are used in these experiments. Coils, Sectioned. A device for prolonging the range of magnetic attraction. It consists of a series of magnetizing coils traversed by an iron plunger. As it passes through them, the current is turned off the one in the rear or passing to the rear and turned into the next one in advance. The principle was utilized in one of Page's electric motors about 1850, and later by others. The port-electric railroad, q. v., utilizes the same principle. 139 STANDARD ELECTRICAL DICTIONARY. Collecting Ring. In some kinds of generators instead of the commutator a pair of collecting rings of metal, insulated from the machine and from each other, are carried on the armature shaft. A brush, q. v., presses on each, and the circuit terminals connect to these two brushes. Such rings are employed often on alternating current generators, where the current does not have to be changed or commuted. Collecting rings with their brushes are used also where a current has to be communicated to a revolving coil or circuit as in the magnetic car wheel, the cut of which is repeated here. The coil of wire surrounding the wheel and rotating with it has to receive current. This it receives through the two stationary brushes which press upon two insulated metallic rings, surrounding the shaft. The terminals of the coil connect one to each ring. Thus while the coil rotates it constantly receives current, the brushes being connected to the actuating circuit. Fig. 105. MAGNETIC CAR WHEEL SHOWING COLLECTING RINGS AND BRUSHES. Collector. (a) A name for the brush, q. v., in mechanical electric generators, such as dynamos, a pair of which collectors or brushes press on the commutator or collecting rings, and take off the current. (b) The pointed connections leading to the prime conductor on a static machine for collecting the electricity; often called combs. The points of the combs or collectors face the statically charged rotating glass plate or cylinder of the machine. Colombin. The insulating material between the carbons in a Jablochkoff candle or other candle of that type. Kaolin was originally used. Later a mixture of two parts calcium sulphate (plaster of Paris) and one part barium sulphate (barytes) was substituted. The colombin was three millimeters (.12 inch) wide, and two millimeters (.08 inch) thick. (See Candle, Jablochkoff.) Column, Electric. An old name for the voltaic pile, made up of a pile of discs of copper and zinc, with flannel discs, wet with salt solution or dilute acid, between each pair of plates. 140 STANDARD ELECTRICAL DICTIONARY. Comb. A bar from which a number of teeth project, like the teeth of a comb. It is used as a collector of electricity from the plate of a frictional or influence electric machine; it is also used in a lightning arrester to define a path of very high resistance but of low self-induction, for the lightning to follow to earth. Communicator. The instrument by which telegraph signals are transmitted is sometimes thus termed. Commutator. In general an apparatus for changing. It is used on electric current generators, and motors, and on induction coils, and elsewhere, for changing the direction of currents, and is of a great variety of types. Synonym--Commuter (but little used). Fig. 106. DYNAMO OR MOTOR COMMUTATOR. Commutator Bars. The metallic segments of a dynamo or motor commutator. Commutator, Flats in. A wearing away or lowering in level of one or more metallic segments of a commutator. They are probably due in many cases to sparking, set up by periodic springing in the armature mounting, or by defective commutator connections. Commutator of Current Generators and Motors. In general a cylinder, formed of alternate sections of conducting and non-conducting material, running longitudinally or parallel with the axis. Its place is on the shaft of the machine, so that it rotates therewith. Two brushes, q. v., or pieces of conducting material, press upon its surface. 141 STANDARD ELECTRICAL DICTIONARY. As a part of electric motors and generators, its function is to collect the currents produced by the cutting of lines of force so as to cause them all to concur to a desired result. The cut shows the simplest form of commutator, one with but two divisions. Its object may be to enable a current of constant direction to be taken from a rotating armature, in which the currents alternate or change direction once in each rotation. It is carried by the shaft A of the armature and rotates with it. It consists of two leaves, S S, to which the terminals of the armature are connected. Two springs, W W, the terminals of the outer circuit, press against the leaves. The springs which do this take off the current. It is so placed, with reference to the springs and armature, that just as the current changes in direction, each leaf changes from one spring to the other. Thus the springs receive constant direction currents. The changing action of this commutator appears in its changing the character of the current from alternating to constant. Were two insulated collecting rings used instead of a commutator, the current in the outer circuit would be an alternating one. On some dynamos the commutator has a very large number of leaves. Taking the Gramme ring armature, there must be as many divisions of the commutator as there are connections to the coils. In this case the function of the commutator is simply to lessen friction, for the brushes could be made to take current from the coils directly outside of the periphery of the ring. Commutator, Split Ring. A two-division commutator for a motor; it consists of two segments of brass or copper plate, bent to arcs of a circle, and attached to an insulating cylinder. They are mounted on the revolving spindle, which carries the armature, and acts as a two part commutator. For an example of its application, see Armature, Revolving, Page's. (See also Fig. 107.) Fig. 107. SECTION OF SPLIT RING COMMUTATOR, WITH BRUSHES. Compass. An apparatus for utilizing the directive force of the earth upon the magnetic needle. It consists of a circular case, within which is poised a magnetized bar of steel. This points approximately to the north, and is used on ships and elsewhere to constantly show the direction of the magnetic meridian. Two general types are used. In one the needle is mounted above a fixed "card" or dial, on which degrees or points of the compass, q. v., are inscribed. In the other the card is attached to the needle and rotates with it. The latter represents especially the type known as the mariner's compass. (See Compass, Mariner's--Compass, Spirit, and other titles under compass, also Magnetic Axis--Magnetic Elements.) The needle in good compasses carries for a bearing at its centre, a little agate cup, and a sharp brass pin is the point of support. Compass, Azimuth. A compass with sights on one of its diameters; used in determining the magnetic bearing of objects. 142 STANDARD ELECTRICAL DICTIONARY. Compass Card. The card in a compass; it is circular in shape, and its centre coincides with the axis of rotation of the magnetic needle; on it are marked the points of the compass, at the ends generally of star points. (See Compass, Points of the.) It may be fixed, and the needle may be poised above it, or it may be attached to the needle and rotate with it. Compass, Declination. An instrument by which the magnetic declination of any place may be determined. It is virtually a transit instrument and compass combined, the telescope surmounting the latter. In the instrument shown in the cut, L is a telescope mounted by its axis, X, in raised journals with vernier, K, and arc x, for reading its vertical angle, with level n. The azimuth circle, Q, R, is fixed. A vernier, V is carried by the box, A, E, and both turn with the telescope. A very light lozenge-shaped magnetic needle, a, b, is pivoted in the exact centre of the graduated circles, Q R, and M. The true meridian is determined by any convenient astronomical method, and the telescope is used for the purpose. The variation of the needle from the meridian thus determined gives the magnetic declination. FIG. 108. DECLINATION COMPASS. Compass, Inclination. A magnetic needle mounted on a horizontal axis at its centre of gravity, so as to be free to assume the dip, or magnetic inclination, when placed in the magnetic meridian. It moves over the face of a vertical graduated circle, and the frame also carries a spirit level and graduated horizontal circle. In use the frame is turned until the needle is vertical. Then the axis of suspension of the needle is in the magnetic meridian. The vertical circle is then turned through 90° of the horizon, which brings the plane of rotation of the needle into the magnetic meridian, when it assumes the inclination of the place. 143 STANDARD ELECTRICAL DICTIONARY. Compass, Mariner's. A compass distinguished by the card being attached to and rotating with the needle. A mark, the "lubber's mark" of the sailors is made upon the case. This is placed so that the line connecting it, and the axis of rotation of the card is exactly in a plane, passing through the keel of the ship. Thus however the ship may be going, the point of the card under or in line with the "lubber's mark," shows how the ship is pointing. The case of the mariner's compass is often bowl-shaped and mounted in gimbals, a species of universal joint, so as to bc always horizontal. (See Compass, Spirit-Gimbals.) FIG. 109. MARINER'S COMPASS. Compass, Points of the. The circle of the horizon may bc and is best referred to angular degrees. It has also been divided into thirty-two equiangular and named points. A point is 11.25°. The names of the points are as follows: North, North by East, North North-east, North-east by North, North-east, North-east by East, East North-east, East by North, East, East by South, East South-east, South-east by East, South-east, South-east by South, South South-east, South by East, South, South by West, South South-west, South-west by South, South-west, South-west by West, West South-west, West by South, West, West by North, West North-west, North-west by West, North-west, North West by North, North North-west, North by West. They are indicated by their initials as N. N. W., North North-west, N. by W., North by West. Compass, Spirit. A form of mariner's compass. The bowl or case is hermetically sealed and filled with alcohol or other nonfreezing liquid. The compass card is made with hollow compartments so as nearly to float. In this way the friction of the pivot or point of support is greatly diminished, and the compass is far more sensitive. Compass, Surveyor's. A species of theodolite; a telescope with collimation lines, mounted above a compass, so as to be applicable for magnetic surveys. Its use is to be discouraged on account of the inaccuracy and changes in declination of the magnetic needle. 144 STANDARD ELECTRICAL DICTIONARY. Compensating Resistances. In using a galvanometer shunt the total resistance of the circuit is diminished so that in some cases too much current flows through it; in such case additional resistance, termed as above, is sometimes introduced in series. The shunt in parallel with the galvanometer is thus compensated for, and the experimental or trial circuit does not take too much current. Complementary Distribution. Every distribution of electricity has somewhere a corresponding distribution, exactly equal to it of opposite electricity; the latter is the complimentary distribution to the first, and the first distribution is also complimentary to it. Component. A force may always be represented diagrammatically by a straight line, terminating in an arrow-head to indicate the direction, and of length to represent the intensity of the force. The line may always be assumed to represent the diagonal of a parallelogram, two of whose sides are represented by lines starting from the base of the arrow, and of length fixed by the condition that the original force shall be the diagonal of the parallelogram of which they are two contiguous sides; such lines are called components, and actually represent forces into which the original force may always be resolved. The components can have any direction. Thus the vertical component of a horizontal force is zero; its horizontal component is equal to itself. Its 450 component is equal to the square root of one-half of its square. Condenser. An appliance for storing up electrostatic charges: it is also called a static accumulator. The telegraphic condenser consists of a box packed full of sheets of tinfoil. Between every two sheets is a sheet of paraffined paper, or of mica. The alternate sheets of tinfoil are connected together, and each set has its own binding post. (See Accumulator, Electrostatic.) Condenser, Sliding. An apparatus representing a Leyden jar whose coatings can be slid past each other. This diminishes or increases the facing area, and consequently in almost exactly similar ratio diminishes or increases the capacity of the condenser. Conductance. The conducting power of a given mass of specified material of specified shape and connections. Conductance varies in cylindrical or prismatic conductors, inversely as the length, directly as the cross-section, and with the conductivity of the material. Conductance is an attribute of any specified conductor, and refers to its shape, length and other factors. Conductivity is an attribute of any specified material without direct reference to its shape, or other factors. Conduction. The process or act of conducting a current. 145 STANDARD ELECTRICAL DICTIONARY. Conductivity. The relative power of conducting the electric current possessed by different substances. A path for the current through the ether is opened by the presence of a body of proper quality, and this quality, probably correlated to opacity, is termed conductivity. There is no perfect conductor, all offer some resistance, q. v., and there is hardly any perfect non-conductor. It is the reverse and reciprocal of resistance. Conductivity, Specific. The reciprocal of specific resistance. (See Resistance--Specific.) Conductivity, Unit of. The reciprocal of the ohm; it is a more logical unit, but has never been generally adopted; as a name the title mho (or ohm written backwards) has been suggested by Sir William Thomson, and provisionally adopted. Conductivity, Variable. The conductivity for electric currents of conductors varies with their temperature, with varying magnetization, tension, torsion and compression. Conductor. In electricity, anything that permits the passage of an electric current. Any disturbance in the ether takes the form of waves because the ether has restitutive force or elasticity. In a conductor, on the other hand, this force is wanting; it opens a path through the ether and a disturbance advances through it from end to end with a wave front, but with no succession of waves. This advance is the beginning of what is termed a current. It is, by some theorists, attributed to impulses given at all points along the conductor through the surrounding ether, so that a current is not merely due to an end thrust. If ether waves preclude a current on account of their restitutive force, ether waves cannot be maintained in a conductor, hence conductors should be opaque to light, for the latter is due to ether waves. This is one of the more practical every day facts brought out in Clerk Maxwell's electromagnetic theory of light. The term conductor is a relative one, as except a vacuum there is probably no substance that has not some conducting power. For relative conducting power, tables of conductivity, q. v., should be consulted. The metals beginning with silver are the best conductors, glass is one of the worst. [Transcriber's note: See "ether" for contemporary comments on this now discarded concept.] Conductor, Anti-Induction. A current conductor arranged to avoid induction from other lines. Many kinds have been invented and made the subject of patents. A fair approximation may be attained by using a through metallic circuit and twisting the wires composing it around each other. Sometimes concentric conductors, one a wire and the other a tube, are used, insulated, one acting as return circuit for the other. Conductor, Conical. A prime conductor of approximately conical shape, but rounded on all points and angles. Its potential is highest at the point. 146 STANDARD ELECTRICAL DICTIONARY. Conductor, Imbricated. A conductor used in dynamo armatures for avoiding eddy currents, made by twisting together two or more strips of copper. Conductor, Prime. A body often cylindrical or spherical in shape, in any case with no points or angles, but rounded everywhere, whose surface, if the conductor itself is not metallic, is made conducting by tinfoil or gold leaf pasted over it. It is supported on an insulating stand and is used to collect or receive and retain static charges of electricity. Conductors, Equivalent. Conductors of identical resistance. The quotient of the length divided by the product of the conductivity and cross-section must be the same in each, if each is of uniform diameter. Conjugate. adj. Conjugate coils or conductors are coils placed in such relation that the lines of force established by one do not pass through the coils of the other. Hence variations of current in one produce no induced currents in the other. Connect. v. To bring two ends of a conductor together, or to bring one end of a conductor in connection with another, or in any way to bring about an electrical connection. Connector. A sleeve with screws or other equivalent device for securing the ends of wires in electrical contact. A binding-post, q. v., is an example. Sometimes wire spring-catches are used, the general idea being a device that enables wires to be connected or released at will without breaking off or marring their ends. The latter troubles result from twisting wires together. Consequent Poles. A bar magnet is often purposely or accidentally magnetized so as to have both ends of the same polarity, and the center of opposite polarity. The center is said to comprise two consequent poles. (See Magnet, Anomalous.) Conservation of Electricity. As every charge of electricity has its equal and opposite charge somewhere, near or far, more or less distributed, the sum of negative is equal always to the sum of positive electrical charges. For this doctrine the above title was proposed by Lippman. Contact Breaker. Any contrivance for closing a circuit, and generally for opening and closing in quick succession. An old and primitive form consisted of a very coarsely cut file. This was connected to one terminal, and the other terminal was drawn over its face, making and breaking contact as it jumped from tooth to tooth. (See Circuit Breaker--do. Automatic, etc.--do. Wheel-do. Pendulum.) 147 STANDARD ELECTRICAL DICTIONARY. Contact, Electric. A contact between two conductors, such that a current can flow through it. It may be brought about by simple touch or impact between the ends or terminals of a circuit, sometimes called a dotting contact, or by a sliding or rubbing of one terminal on another, or by a wheel rolling on a surface, the wheel and surface representing the two terminals. There are various descriptions of contact, whose names are self-explanatory. The term is applied to telegraph line faults also, and under this, includes different descriptions of contact with neighboring lines, or with the earth. Contact Electricity. When two dissimilar substances are touched they assume different electric potentials. If conductors, their entire surfaces are affected; if dielectrics, only the surfaces which touch each other. (See Contact Theory.) Contact Faults. A class of faults often called contacts, due to contact of the conductor of a circuit with another conductor. A full or metallic contact is where practically perfect contact is established; a partial contact and intermittent contact are self-explanatory. Contact Point. A point, pin or stud, often of platinum, arranged to come in contact with a contact spring, q. v., or another contact point or surface, under any determined conditions. Contact Potential Difference. The potential difference established by the contact of two dissimilar substances according to the contact theory, q. v. Contact Series. An arrangement or tabulation of substances in pairs, each intermediate substance appearing in two pairs, as the last member of the first, and first member of the succeeding pair, with the statement of the potential difference due to their contact, the positively electrified substance coming first. The following table of some contact potentials is due to Ayrton and Perry: CONTACT SERIES. Difference of Potential in Volts. Zinc--Lead .210 Lead--Tin .069 Tin--Iron .313 Iron--Copper .146 Copper--Platinum .238 Platinum-Carbon .113 The sum of these differences is 1.089, which is the contact potential between zinc and carbon. Volta's Law refers to this and states that-- The difference of potential produced by the contact of any two substances is equal to the sum of the differences of potentials between the intervening substances in the contact series. It is to be remarked that the law should no longer be restricted to or stated only for metals. 148 STANDARD ELECTRICAL DICTIONARY. Contact-spring. A spring connected to one lead of an electric circuit, arranged to press against another spring, or contact point, q. v., under any conditions determined by the construction of the apparatus. (See Bell, Electric--Coil, Induction.) Contact Theory. A theory devised to explain electrification, the charging of bodies by friction, or rubbing, and the production of current by the voltaic battery. It holds that two bodies, by mere contact become oppositely electrified. If such contact is increased in extent by rubbing together, the intensity of their electrification is increased. This electrification is accounted for by the assumption of different kinetic energy, or energy of molecular motion, possessed by the two bodies; there being a loss and gain of energy, on the two sides respectively, the opposite electrifications are the result. Then when separated, the two bodies come apart oppositely electrified. The above accounts for the frictional production of electricity. In the voltaic battery, a separation of the atoms of hydrogen and oxygen, and their consolidation into molecules occurs, and to such separation and the opposite electrification of the electrodes by the oxygen and hydrogen, the current is attributed, because the hydrogen goes to one electrode, and the oxygen to the other, each giving up or sharing its own charge with the electrodes to which it goes. If zinc is touched to copper, the zinc is positively and the copper negatively electrified. In the separation of hydrogen and oxygen, the hydrogen is positively and the oxygen negatively electrified. In the battery, the current is due to the higher contact difference of oxygen and hydrogen compared to that between zinc and copper. It will be seen that the two contact actions in a battery work against each other, and that the current is due to a differential contact action. The zinc in a battery is electrified negatively because the negative electrification of the oxygen is greater in amount than its own positive electrification due to contact with the copper. Contractures. A muscular spasm or tetanus due to the passage of a current of electricity; a term in electro-therapeutics. Controlling Field. The magnetic or electro-magnetic field, which is used in galvanometers to control the magnetic needle, tending to restore it to a definite position whenever it is turned therefrom. It may be the earth's field or one artificially produced. Controlling Force. In galvanometers and similar instruments, the force used to bring the needle or indicator back to zero. (See Controlling Field--Electro-Magnetic Control--Gravity Control--Magnetic Control--Spring Control.) 149 STANDARD ELECTRICAL DICTIONARY. Convection, Electric. The production of blasts or currents of air (convection streams) from points connected to statically charged conductors. The term is sometimes applied to electric convection of heat. (See Convection of Heat, Electric.) Convection, Electrolytic. The resistance of acidulated water as a true conductor is known to be very, almost immeasurably, high. As an electrolytic, its resistance is very much lower. Hence the current produced between immersed electrodes is theoretically almost null, unless the difference of potential between them is high enough to decompose the liquid. Yet a feeble current too great for a true conduction current is sometimes observed when two electrodes with potential difference too low to cause decomposition are immersed in it. Such a current is termed an electrolytic convection current. It is supposed to be due to various causes. Some attribute it to the presence of free oxygen from the air, dissolved in the water with which the hydrogen combines. Others attribute it to the diffusion of the gases of decomposition in the solution; others assume a partial polarization of the molecules without decomposition. Other theories are given, all of which are unsatisfactory. The term is due to Helmholtz. Convection of Heat, Electric. The effect of a current upon the distribution of heat in an unevenly heated conductor. In some, such as copper, the current tends to equalize the varying temperatures; the convection is then said to be positive, as comparable to that of water flowing through an unequally heated tube. In others, such as platinum or iron, it is negative, making the heated parts hotter, and the cooler parts relatively cooler. The effect of the electric current in affecting the distribution of heat in unequally heated metal (Thomson's effect. q. v.), is sometimes so termed. If a current passes through unequally heated iron it tends to increase the difference of temperature, and the convection is negative; in copper it tends to equalize the temperature, and the convection is positive. Converter. An induction coil used with the alternating current for changing potential difference and inversely therewith the available current. They generally lower the potential, and increase the current, and are placed between the primary high potential system that connects the houses with the central station, and the secondary low potential system within the houses. A converter consists of a core of thin iron sheets, wound with a fine primary coil of many convolutions, and a coarse secondary coil of few convolutions. The ratio of convolutions gives the ratio of maximum potential differences of their terminals between the primary and secondary coils. The coil may be jacketed with iron to increase the permeance. (See Alternating Current System.) Fig. 110. FERRANTI'S CONVERTER OR TRANSFORMER. Fig. 111. SWINBURNE'S HEDGEHOG TRANSFORMER. 150 STANDARD ELECTRICAL DICTIONARY. Co-ordinates, System of. A system for indicating the position of points in space by reference to fixed lines, intersecting at a determined and arbitrary point 0, termed the origin of co-ordinates. In plane rectangular co-ordinates two lines are drawn through the origin, one horizontal, termed the axis of abscissas, or axis of X. All distances measured parallel to it, if unknown, are indicated by x, and are termed abscissas. The other axis is vertical, and is termed the axis of ordinates, or axis of Y. All distances measured parallel to it, if unknown, are indicated by y and are termed ordinates. Thus by naming its abscissa and ordinate a point has its position with reference to the axes determined, and by indicating the relation between a point, line or curve, and a system of abscissas and ordinates, the properties of a line or curve can be expressed algebraically. Co-ordinates may also be inclined to each other at any other angles, forming oblique co-ordinates; relations may be expressed partly in angles referred to the origin as a centre, giving polar co-ordinates. For solid geometry or calculations in three dimensions, a third axis, or axis of Z, is used, distances parallel to which if unknown are indicated by z. Fig. 112. AXES OF CO-ORDINATES. 151 STANDARD ELECTRICAL DICTIONARY. Cooling Box. In a hydroelectric machine, q. v., a conduit or chest through which the steam passes on its way to the nozzles. Its object is to partially condense the steam so as to charge it with water vesicles whose friction against the sides of the nozzles produces the electrification . 152 STANDARD ELECTRICAL DICTIONARY. Copper. A metal; one of the elements. Symbol, Cu; atomic weight, 63.5; equivalent, 63.5 and 31.75; valency, 1 and 2; specific gravity, 8.96. It is a conductor of electricity, whose conductivity is liable to vary greatly on account of impurities. Annealed. Hard drawn. Relative resistance (Silver = 1), 1.063 1.086 Specific resistance, 1.598 1.634 microhms. Resistance of a wire at 0° C. (32° F.), Annealed. Hard Drawn. (a) 1 foot long, weighing 1 grain, .2041 ohms .2083 ohms. (b) 1 foot long, 1/1000 inch thick, 9.612 " 9.831 " (c) 1 meter long, weighing 1 gram, .1424 " .1453 " (d) 1 meter long, 1 millimeter thick, .02034 " .02081 " microhm. microhm. Resistance of 1 inch cube at 0°C. (32° F.) .6292 .6433 Percentage of resistance change, per 1° C. (1.8° F.) at about 20° C. (68° F.) = 0.388 per cent. Electro-chemical Equivalent (Hydrogen = .0105) Cuprous .6667 Cupric .3334 In electricity it has been very extensively used as the negative plate of voltaic batteries. It has its most extensive application as conductors for all classes of electrical leads. Copper Bath. A solution of copper used for depositing the metal in the electroplating process. For some metals, such as zinc or iron, which decompose copper sulphate solution, special baths have to be used. The regular bath for copper plating is the following: To water acidulated with 8 to 10 percent. of sulphuric acid as much copper sulphate is added as it will take up at the ordinary temperature. The saturated bath should have a density of 1.21. It is used cold and is kept in condition by the use of copper anodes, or fresh crystals may be added from time to time. For deposition on zinc, iron, tin and other metals more electropositive than copper, the following baths may be used, expressed in parts by weight: Tin Iron and Steel. Cast Iron Cold Hot. and Zinc. Zinc. Sodium Bisulphate, 500 200 300 100 Potassium Cyanide, 500 700 500 700 Sodium Carbonate, 1000 500 --- --- Copper Acetate, 475 500 350 450 Aqua Ammoniae, 350 300 200 150 Water, 2500 2500 2500 2500 These are due to Roseleur. 153 STANDARD ELECTRICAL DICTIONARY. Copper Stripping Bath. There is generally no object in stripping copper from objects. It can be done with any of the regular copper baths using the objects to be stripped as anode. The danger of dissolving the base itself and thereby injuring the article and spoiling the bath is obvious. Cord Adjuster. A device for shortening or lengthening the flexible cord, or flexible wire supplying the current, and by which an incandescent lamp is suspended. It often is merely a little block of wood perforated with two holes through which the wires pass, and in which they are retained in any desired position by friction and their own stiffness. Fig. 113. FLEXIBLE CORD ADJUSTER. Cord, Flexible. A pair of flexible wire conductors, insulated lightly, twisted together and forming apparently a cord. They are used for minor services, such as single lamps and the like, and are designated according to the service they perform, such as battery cords, dental cords (for supplying dental apparatus) and other titles. Core. (a) The conductor or conductors of an electric cable. (See Cable Core.) (b) The iron mass, generally central in an electro-magnet or armature, around which the wire is coiled. It acts by its high permeance to concentrate or multiply the lines of force, thus maintaining a more intense field. (See Armature--Magnet, Electro--Magnet, Field--Core, Laminated). In converters or transformers (See Converter) it often surrounds the wire coils. Core-discs. Discs of thin wire, for building up armature cores. (See Laminated Core.) The usual form of core is a cylinder. A number of thin discs of iron are strung upon the central shaft and pressed firmly together by end nuts or keys. This arrangement, it will be seen, gives a cylinder as basis for winding the wire on. Core-discs, Pierced. Core-discs for an armature of dynamo or motor, which are pierced around the periphery. Tubes of insulating material pass through the peripheral holes, and through these the conductors or windings are carried. The conductors are thus embedded in a mass of iron and are protected from eddy currents, and they act to reduce the reluctance of the air gaps. From a mechanical point of view they are very good. For voltages over 100 they are not advised. Synonym--Perforated Core-discs. 154 STANDARD ELECTRICAL DICTIONARY. Core-discs, Segmental. Core-discs made in segments, which are bolted together to form a complete disc or section of the core. The plan is adopted principally on large cores. The discs thus made up are placed together to form the core exactly as in the case of ordinary one piece discs. Fig. 114. PIERCED OR PERFORATED CORE-DISC. Core-discs, Toothed. Core-discs of an armature of a dynamo or motor, which discs are cut into notches on the periphery. These are put together to form the armature core, with the notches corresponding so as to form a series of grooves in which the wire winding is laid. This construction reduces the actual air-gaps, and keeps the wires evenly spaced. Distance-pieces of box-wood, m, m, are sometimes used to lead the wires at the ends of the armature. Fig. 115. TOOTHED CORE-DISC. Core, Laminated. A core of an armature, induction coil or converter or other similar construction, which is made up of plates insulated more or less perfectly from each other. The object of lamination is to prevent the formation of Foucault currents. (See Currents, Foucault.) As insulation, thin shellacked paper may be used, or sometimes the superficial oxidation of the plates alone is relied on. The plates, in general, are laid perpendicular to the principal convolutions of the wire, or parallel to the lines of force. The object is to break up currents, and such currents are induced by the variation in intensity of the field of force, and their direction is perpendicular to the lines of force, or parallel to the inducing conductors. A core built up of core discs is sometimes termed a tangentially laminated core. Made up of ribbon or wire wound coil fashion, it is termed a radially laminated core. 155 STANDARD ELECTRICAL DICTIONARY. Core Ratio. In a telegraph cable the ratio existing between the diameter of the conducting core and the insulator. To get a ratio approximately accurate in practical calculations, the diameter of the core is taken at 5 per cent. less than its actual diameter. The calculations are those referring to the electric constants of the cable, such as its static capacity and insulation resistance. Core, Ribbon. For discoidal ring-shaped cores of armatures, iron ribbon is often used to secure lamination and prevent Foucault currents. Synonym--Tangentially Laminated Core. Core, Ring. A core for a dynamo or motor armature, which core forms a complete ring. Core, Stranded. In an electric light cable, a conducting core made up of a group of wires laid or twisted together. Core, Tubular. Tubes used as cores for electro-magnets. For very small magnetizing power, tubular cores are nearly as efficient as solid ones in straight magnets, because the principal reluctance is due to the air-path. On increasing the magnetization the tubular core becomes less efficient than the solid core, as the reluctance of the air-path becomes proportionately of less importance in the circuit. Corpusants. The sailors' name for St. Elmo's Fire, q. v. Coulomb. The practical unit of quantity of electricity. It is the quantity passed by a current of one ampere intensity in one second. It is equal to 1/10 the C. G. S. electro-magnetic unit of quantity, and to 3,000,000,000 C. G. S. electrostatic units of quantity. It corresponds to the decomposition of .0935 milligrams of water, or to the deposition of 1.11815 milligrams of silver. [Transcriber's note: A coulomb is approximately 6.241E18 electrons. Two point charges of one coulomb each, one meter apart, exerts a force of 900,000 metric tons.] Coulomb's Laws of Electrostatic Attraction and Repulsion. 1. The repulsions or attractions between two electrified bodies are in the inverse ratio of the squares of their distance. 2. The distance remaining the same, the force of attraction or repulsion between two electrified bodies is directly as the product of the quantities of electricity with which they are charged. 156 STANDARD ELECTRICAL DICTIONARY. Counter, Electric. A device for registering electrically, or by electro-magnetic machinery, the revolutions of shafts, or any other data or factors. Counter-electro-motive Force. A potential difference in a circuit opposed to the main potential difference, and hence, resisting the operation of the latter, and diminishing the current which would be produced without it. It appears in electric motors, which, to a certain extent, operate as dynamos and reduce the effective electro-motive force that operates them. It appears in the primary coils of induction coils, and when the secondary circuit is open, is almost equal to the main electro-motive force, so that hardly any current can go through them under such conditions. It appears in galvanic batteries, when hydrogen accumulates on the copper plate, and in other chemical reactions. A secondary battery is charged by a current in the reverse direction to that which it would normally produce. Its own potential difference then appears as a counter-electro-motive force. Synonym--Back Electro-motive Force. Counter-electro-motive Force of Polarization. To decompose a solution by electrolysis, enough electro-motive force is required to overcome the energy of composition of the molecule decomposed. A part of this takes the form of a counter-electromotive force, one which, for a greater or less time would maintain a current in the opposite direction if the original source of current were removed. Thus in the decomposition of water, the electrodes become covered, one with bubbles of oxygen, the others with bubbles of hydrogen; this creates a counter E. M. F. of polarization. In a secondary battery, the working current may be defined as due to this cause. Synonym--Back Electro-motive Force of Polarization. Couple. Two forces applied to different points of a straight line, when opposed in direction or unequal in amount, tend to cause rotation about a point intermediate between their points of application and lying on the straight line. Such a pair constitute a couple. Couple, Voltaic or Galvanic. The combination of two electrodes, and a liquid or liquids, the electrodes being immersed therein, and being acted on differentially by the liquid or liquids. The combination constitutes a source of electro-motive force and consequently of current. It is the galvanic or voltaic cell or battery. (See Battery, Voltaic--Contact Theory--Electro-motive Force--Electro-motive Series.) Coupling. The joining of cells of a galvanic battery, of dynamos or of other devices, so as to produce different effects as desired. 157 STANDARD ELECTRICAL DICTIONARY Couple, Astatic. An astatic couple is a term sometimes applied to astatic needles, q.v. C. P. (a) An abbreviation of or symbol for candle power, q. v. (b) An abbreviation of chemically pure. It is used to indicate a high degree of purity of chemicals. Thus, in a standard Daniell battery, the use of C. P. chemicals may be prescribed or advised. Crater. The depression that forms in the positive carbon of a voltaic arc. (See Arc, Voltaic.) Creeping. A phenomenon of capillarity, often annoying in battery jars. The solution, by capillarity, rises a little distance up the sides, evaporates, and as it dries more creeps up through it, and to a point a little above it. This action is repeated until a layer of the salts may form over the top of the vessel. To avoid it, paraffine is often applied to the edges of the cup, or a layer of oil, often linseed oil, is poured on the battery solution, Crith. The weight of a litre of hydrogen at 0º C. (32º F.), and 760 mm. (30 inches) barometric pressure. It is .0896 grams. The molecular weight of any gas divided by 2 and multiplied by the value of the crith, gives the weight of a litre of the gas in question. Thus a litre of electrolytic gas, a mixture of two molecules of hydrogen for one of oxygen, with a mean molecular weight of 12, weighs (12/2) * .0896 or .5376 gram. Critical Speed. (a) The speed of rotation at which a series dynamo begins to excite its own field. (b) In a compound wound dynamo, the speed at which the same potential is generated with the full load being taken from the machine, as would be generated on open circuit, in which case the shunt coil is the only exciter. The speed at which the dynamo is self-regulating. (c) In a dynamo the rate of speed when a small change in the speed of rotation produces a comparatively great change in the electro-motive force. It corresponds to the same current (the critical current) in any given series dynamo. Cross. (a) A contact between two electric conductors; qualified to express conditions as a weather cross, due to rain, a swinging cross when a wire swings against another, etc. (b) vb. To make such contact. Cross-Connecting Board. A special switch board used in telephone exchanges and central telegraph offices. Its function is, by plugs and wires, to connect the line wires with any desired section of the main switchboard. The terminals of the lines as they enter the building are connected directly to the cross-connecting board. 158 STANDARD ELECTRICAL DICTIONARY. Cross Connection. A method of disposing of the effects of induction from neighboring circuits by alternately crossing the two wires of a metallic telephone circuit, so that for equal intervals they lie to right and left, or one above, and one below. [Transcriber's note: Also used to cancel the effect of variations in the ambient magnetic field, such as solar activity.] Crossing Wires. The cutting out of a defective section in a telegraph line, by carrying two wires from each side of the defective section across to a neighboring conductor, pressing it for the time into service and cutting the other wire if necessary. Cross-magnetizing Effect. A phase of armature interference. The current in an armature of a dynamo or motor is such as to develop lines of force approximately at right angles to those of the field. The net cross-magnetizing effect is such component of these lines, as is at right angles to the lines produced by the field alone. Cross-over Block. A piece of porcelain or other material shaped to receive two wires which are to cross each other, and hold them so that they cannot come in contact. It is used in wiring buildings, and similar purposes. (See Cleat, Crossing.) Cross Talk. On telephone circuits by induction or by contact with other wires sound effects of talking are sometimes received from other circuits; such effects are termed cross talk. Crucible, Electric. A crucible for melting difficultly fusible substances, or for reducing ores, etc., by the electric arc produced within it. Sometimes the heating is due more to current incandescence than to the action of an arc. Fig. 116. ELECTRIC FURNACE OR CRUCIBLE. Crystallization, Electric. Many substances under proper conditions take a crystalline form. The great condition is the passage from the fluid into the solid state. When such is brought about by electricity in any way, the term electric crystallization may be applied to the phenomenon. A solution of silver nitrate for instance, decomposed by a current, may give crystals of metallic silver. 159 STANDARD ELECTRICAL DICTIONARY. Cup, Porous. A cup used in two-fluid voltaic batteries to keep the solutions separate to some extent. It forms a diaphragm through which diffusion inevitably takes place, but which is considerably retarded, while electrolysis and electrolytic convection take place freely through its walls. As material, unglazed pottery is very generally used. In some batteries the cup is merely a receptacle for the solid depolarizer. Thus, in the Leclanché battery, the cup contains the manganese dioxide and graphite in which the carbon electrode is embedded, but does not separate two solutions, as the battery only uses one. Nevertheless, the composition of the solution outside and inside may vary, but such variation is incidental only, and not an essential of the operation. Current. The adjustment, or effects of a continuous attempt at readjustment of potential difference by a conductor, q. v., connecting two points of different potential. A charged particle or body placed in a field of force tends to move toward the oppositely charged end or portion of the field. If a series of conducting particles or a conducting body are held so as to be unable to move, then the charge of the field tends, as it were, to move through it, and a current results. It is really a redistribution of the field and as long as such redistribution continues a current exists. A current is assumed to flow from a positive to a negative terminal; as in the case of a battery, the current in the outer circuit is assumed to flow from the carbon to the zinc plate, and in the solution to continue from zinc to carbon. As a memoria technica the zinc may be thought of as generating the current delivering it through the solution to the carbon, whence it flows through the wire connecting them. (See Ohm's Law--Maxwell's Theory of Light--Conductor-Intensity.) [Transcriber's note: Supposing electric current to be the motion of positive charge causes no practical difficulty, but the current is actually the (slight) motion of negative electrons.] Current, After. A current produced by the animal tissue after it has been subjected to a current in the opposite direction for some time. The tissue acts like a secondary battery. The term is used in electro-therapeutics. Current, Alternating. Usually defined and spoken of as a current flowing alternately in opposite directions. It may be considered as a succession of currents, each of short duration and of direction opposite to that of its predecessor. It is graphically represented by such a curve as shown in the cut. The horizontal line may denote a zero current, that is no current at all, or may be taken to indicate zero electro-motive force. The curve represents the current, or the corresponding electro-motive forces. The further from the horizontal line the greater is either, and if above the line the direction is opposite to that corresponding to the positions below the line. Thus the current is alternately in opposite directions, has periods of maximum intensity, first in one and then in the opposite sense, and between these, passing from one direction to the other, is of zero intensity. It is obvious that the current may rise quickly in intensity and fall slowly, or the reverse, or may rise and fall irregularly. All such phases may be shown by the curve, and a curve drawn to correctly represent these variations is called the characteristic curve of such current. It is immaterial whether the ordinates of the curve be taken as representing current strength or electromotive force. If interpreted as representing electro-motive force, the usual interpretation and best, the ordinates above the line are taken as positive and those below as negative. Synonyms--Reversed Current--Periodic Currents. Fig. 117. CHARACTERISTIC CURVE OF ALTERNATING CURRENT. 160 STANDARD ELECTRICAL DICTIONARY. Current, Atomic. A unit of current strength used in Germany; the strength of a current which will liberate in 24 hours (86,400 seconds) one gram of hydrogen gas, in a water voltameter. The atomic current is equal to 1.111 amperes. In telegraphic work the milliatom is used as a unit, comparable to the milliampere. The latter is now displacing it. Current, Charge. If the external coatings of a charged and uncharged jar are placed in connection, and if the inner coatings are now connected, after separating them they are both found to be charged in the same manner. In this process a current has been produced between the outside coatings and one between the inner ones, to which Dove has given the name Charge Current, and which has all the properties of the ordinary discharge current. (Ganot.) Current, Circular. A current passing through a circular conductor; a current whose path is in the shape of a circle. Current, Commuted. A current changed, as regards direction or directions, by a commutator, q. v., or its equivalent. Current, Constant. An unvarying current. A constant current system is one maintaining such a current. In electric series, incandescent lighting, a constant current is employed, and the system is termed as above. In arc lighting systems, the constant current series arrangement is almost universal. 161 STANDARD ELECTRICAL DICTIONARY. Current, Continuous. A current of one direction only; the reverse of an alternating current. (See Current, Alternating.) Current, Critical. The current produced by a dynamo at its critical speed; at that speed when a slight difference in speed produces a great difference in electro-motive force. On the characteristic curve it corresponds to the point where the curve bends sharply, and where the electro-motive force is about two-thirds its maximum. Current, Daniell/U.S. , Daniell/Siemens' Unit. A unit of current strength used in Germany. It is the strength of a current produced by one Daniell cell in a circuit of the resistance of one Siemens' unit. The current deposits 1.38 grams of copper per hour. It is equal to 1.16 amperes. Current, Demarcation. In electro-therapeutics, a current which can be taken from an injured muscle, the injured portion acting electro-negatively toward the uninjured portion. Current Density. The current intensity per unit of cross-sectional area of the conductor. The expression is more generally used for electrolytic conduction, where the current-density is referred to the mean facing areas of the electrodes, or else to the facing area of the cathode only. The quality of the deposited metal is intimately related to the current density. (See Burning.) Proper Current Density for Electroplating Amperes Per Square Foot of Cathode.--(Urquhart.) Copper, Acid Bath. 5.0 to 10.0 " Cyanide Bath, 3.0 " 5.0 Silver, Double Cyanide, 2.0 " 5.0 Gold, Chloride dissolved in Potassium Cyanide, 1.0 " 2.0 Nickel, Double Sulphate, 6.6 " 8.0 Brass, Cyanide, 2.0 " 3.0 Current, Diacritical. A current, which, passing through a helix surrounding an iron core, brings it to one-half its magnetic saturation, q. v. Current, Diaphragm. If a liquid is forced through a diaphragm, a potential difference between the liquid on opposite sides of the diaphragm is maintained. Electrodes or terminals of platinum may be immersed in the liquid, and a continuous current, termed a diaphragm current, may be taken as long as the liquid is forced through the diaphragm. The potential difference is proportional to the pressure, and also depends on the nature of the diaphragm and on the liquid. 162 STANDARD ELECTRICAL DICTIONARY. Current, Direct. A current of unvarying direction, as distinguished from an alternating current. It may be pulsatory or intermittent in character, but must be of constant direction. Current, Direct Induced. On breaking a circuit, if it is susceptible of exercising self-induction, q. v., an extra current, in the direction of the original is induced, which is called "direct" because in the same direction as the original. The same is produced by a current in one circuit upon a parallel one altogether separated from it. (See Induction, Electro-Magnetic-Current, Extra.) Synonym--Break Induced Current. Current, Direction of. The assumed direction of a current is from positively charged electrode to negatively charged one; in a galvanic battery from the carbon or copper plate through the outer circuit to the zinc plate and back through the electrolyte to the carbon or copper plate. (See Current.) [Transcriber's note: Current is caused by the motion of negative electrons, from the negative pole to the positive. The electron was discovered five years after this publication.] Current, Displacement. The movement or current of electricity taking place in a dielectric during displacement. It is theoretical only and can only be assumed to be of infinitely short duration. (See Displacement, Electric.) Currents, Eddy Displacement. The analogues of Foucault currents, hypothetically produced in the mass of a dielectric by the separation of the electricity or by its electrification. (See Displacement.) Current, Extra. When a circuit is suddenly opened or closed a current of very brief duration, in the first case in the same direction, in the other case in the opposite direction, is produced, which exceeds the ordinary current in intensity. A high potential difference is produced for an instant only. These are called extra currents. As they are produced by electro-magnetic induction, anything which strengthens the field of force increases the potential difference to which they are due. Thus the wire may be wound in a coil around an iron core, in which case the extra currents may be very strong. (See Induction, Self-Coil, Spark.) Current, Faradic. A term in medical electricity for the induced or secondary alternating current, produced by comparatively high electro-motive force, such as given by an induction coil or magneto-generator, as distinguished from the regular battery current. 163 STANDARD ELECTRICAL DICTIONARY. Current, Foucault. A current produced in solid conductors, and which is converted into heat (Ganot). These currents are produced by moving the conductors through a field, or by altering the strength of a field in which they are contained. They are the source of much loss of energy and other derangement in dynamos and motors, and to avoid them the armature cores are laminated, the plane of the laminations being parallel to the lines of force. (See Core, Laminated.) The presence of Foucault currents, if of long duration, is shown by the heating of the metal in which they are produced. In dynamo armatures they are produced sometimes in the metal of the windings, especially if the latter are of large diameter. Synonyms--Eddy Currents--Local Currents--Parasitical Currents. Current, Franklinic. In electro-therapeutics the current produced by a frictional electric machine. Current, Induced. The current produced in a conductor by varying the conditions of a field of force in which it is placed; a current produced by induction. Current Induction. Induction by one current on another or by a portion of a current on another portion of itself. (See Induction.) Current Intensity. Current strength, dependent on or defined by the quantity of electricity passed by such current in a given time. The practical unit of current intensity is the ampere, equal to one coulomb of quantity per second of time. Current, Inverse Induced. The current induced in a conductor, when in a parallel conductor or in one having a parallel component a current is started, or is increased in strength. It is opposite in direction to the inducing current and hence is termed inverse. (See Induction, Electro-magnetic.) The parallel conductors may be in one circuit or in two separate circuits. Synonyms--Make-induced Current--Reverse-induced Current. Current, Jacobi's Unit of. A current which will liberate one cubic centimeter of mixed gases (hydrogen and oxygen) in a water voltameter per minute, the gases being measured at 0º C. (32º F.) and 760 mm. (29.92 inches) barometric pressure. It is equal to .0961 ampere. Current, Joint. The current given by several sources acting together. Properly, it should be restricted to sources connected in series, thus if two battery cells are connected in series the current they maintain is their joint current. Current, Linear. A current passing through a straight conductor; a current whose path follows a straight line. 164 STANDARD ELECTRICAL DICTIONARY. Current, Make and Break. A succession of currents of short duration, separated by absolute cessation of current. Such current is produced by a telegraph key, or by a microphone badly adjusted, so that the circuit is broken at intervals. The U. S. Courts have virtually decided that the telephone operates by the undulatory currents, and not by a make and break current. Many attempts have been made to produce a telephone operating by a demonstrable make and break current, on account of the above distinction, in hopes of producing a telephone outside of the scope of the Bell telephone patent. [Transcriber's note: Contemporary long distance telephone service is digital, as this item describes.] Current-meter. An apparatus for indicating the strength of current. (See Ammeter.) Current, Negative. In the single needle telegraph system the current which deflects the needle to the left. Current, Nerve and Muscle. A current of electricity yielded by nerves or muscles. Under proper conditions feeble currents can be taken from nerves, as the same can be taken from muscles. Current, Opposed. The current given by two or more sources connected in opposition to each other. Thus a two volt and a one volt battery may be connected in opposition, giving a net voltage of only one volt, and a current due to such net voltage. Current, Partial. A divided or branch current. A current which goes through a single conductor to a point where one or more other conductors join it in parallel, and then divides itself between the several conductors, which must join further on, produces partial currents. It produces as many partial currents as the conductors among which it divides. The point of division is termed the point of derivation. Synonym--Derived Current. Current, Polarizing. In electro-therapeutics, a constant current. Current, Positive. In the single needle telegraph system the current which deflects the needle to the right. Current, Pulsatory. A current of constant direction, but whose strength is constantly varying, so that it is a series of pulsations of current instead of a steady flow. Current, Rectified. A typical alternating current is represented by a sine curve, whose undulations extend above and below the zero line. If by a simple two member commutator the currents are caused to go in one direction, in place of the sine curve a series of short convex curves following one another and all the same side of the zero line results. The currents all in the same direction, become what is known as a pulsating current. Synonym--Redressed Current. 165 STANDARD ELECTRICAL DICTIONARY. Current, Rectilinear. A current flowing through a rectilinear conductor. The action of currents depending on their distance from the points where they act, their contour is a controlling factor. This contour is determined by the conductors through which they flow. Current Reverser. A switch or other contrivance for reversing the direction of a current in a conductor. Currents, Ampérian. The currents of electricity assumed by Ampere's theory to circulate around a magnet. As they represent the maintenance of a current or of currents without the expenditure of energy they are often assumed to be of molecular dimensions. As they all go in the same sense of rotation and are parallel to each other the result is the same as if a single set of currents circulated around the body of the magnet. More will be found on this subject under Magnetism. The Ampérian currents are purely hypothetical and are predicated on the existence of a field of force about a permanent magnet. (See Magnetism, Ampére's Theory of.) If the observer faces the north pole of a magnet the Ampérian currents are assumed to go in the direction opposite to that of a watch, and the reverse for the south pole. Figs. 118-119 DIRECTION OF AMPÉRIAN CURRENTS. Currents, Angular. Currents passing through conductors which form an angle with each other. Currents, Angular, Laws of. 1. Two rectilinear currents, the directions of which form an angle with each other, attract one another when both approach to or recede from the apex of the angle. 2. They repel one another, if one approaches and the other recedes from the apex of the angle. 166 STANDARD ELECTRICAL DICTIONARY Currents, Earth. In long telegraph lines having terminal grounds or connected to earth only at their ends, potential differences are sometimes observed that are sufficient to interfere with their working and which, of course, can produce currents. These are termed earth-currents. It will be noted that they exist in the wire, not in the earth. They may be of 40 milliamperes strength, quite enough to work a telegraph line without any battery. Lines running N. E. and S. W. are most affected; those running N.W. and S. E. very much less so. These currents only exist in lines grounded at both ends, and appear in underground wires. Hence they are not attributable to atmospheric electricity. According to Wilde they are the primary cause of magnetic storms, q. v., but not of the periodical changes in the magnetic elements. (See Magnetic Elements.) Synonym--Natural Currents. Current, Secondary. (a) A current induced in one conductor by a variation in the current in a neighboring one; the current produced in the secondary circuit of an induction coil or alternating current converter. (b) The current given by a secondary battery. This terminology is not to be recommended. Current, Secretion. In electro-therapeutics, a current due to stimulation of the secretory nerves. Current Sheet. (a) If two terminals of an active circuit are connected to two points of a thin metallic plate the current spreads over or occupies practically a considerable area of such plate, and this portion of the current is a current sheet. The general contour of the current sheet can be laid out in lines of flux. Such lines resemble lines of force. Like the latter, they are purely an assumption, as the current is not in any sense composed of lines. (b) A condition of current theoretically brought about by the Ampérian currents in a magnet. Each molecule having its own current, the contiguous portions of the molecules counteract each other and give a resultant zero current. All that remains is the outer sheet of electric current that surrounds the whole. Current, Sinuous. A current passing through a sinuous conductor. Currents, Multiphase. A term applied to groups of currents of alternating type which constantly differ from each other by a constant proportion of periods of alternation. They are produced on a single dynamo, the winding being so contrived that two, three or more currents differing a constant amount in phase are collected from corresponding contact rings. There are virtually as many windings on the armature as there are currents to be produced. Separate conductors for the currents must be used throughout. Synonyms--Polyphase Currents--Rotatory Currents. 167 STANDARD ELECTRICAL DICTIONARY. Currents of Motion. In electro-therapeutics, the currents produced in living muscle or nerves after sudden contraction or relaxation. Currents of Rest. In electro-therapeutics, the currents traversing muscular or nervous tissue when at rest. Their existence is disputed. Currents, Orders of. An intermittent current passing through a conductor will induce secondary alternating currents in a closed circuit near it. This secondary current will induce a tertiary current in a third closed circuit near it, and so on. The induced currents are termed as of the first, second, third and other orders. The experiment is carried out by Henry's coils. (See Coils, Henry's.) Currents, Thermo-electric. These currents, as produced from existing thermo-electric batteries, are generated by low potential, and are of great constancy. The opposite junctions of the plates can be kept at constant temperatures, as by melting ice and condensing steam, so that an identical current can be reproduced at will from a thermopile. Thermo-electric currents were used by Ohm in establishing his law. (See Ohm's Law.) Current, Swelling. In electro-therapeutics, a current gradually increasing in strength. Current, Undulatory. A current varying in strength without any abrupt transition from action to inaction, as in the make and break current. The current may be continually changing in direction (see Current, Alternating), and hence, of necessity, may pass through stages of zero intensity, but such transition must be by a graduation, not by an abrupt transition. Such current may be represented by a curve, such as the curve of sines. It is evident that the current may pass through the zero point as it crosses the line or changes direction without being a make and break current. When such a current does alternate in direction it is sometimes called a "shuttle current." The ordinary commercial telephone current and the alternating current is of this type. (See Current, Make and Break.) Current, Unit. Unit current is one which in a wire of unit length, bent so as to form an arc of a circle of unit length of radius, would act upon a unit pole (see Magnetic Pole, Unit,) at the center of the circle with unit force. Unit length is the centimeter; unit force is the dyne. [Transcriber's note: The SI definition of an ampere: A current in two straight parallel conductors of infinite length and negligible cross-section, 1 metre apart in vacuum, would produce a force equal to 2E-7 newton per metre of length.] 168 STANDARD ELECTRICAL DICTIONARY. Current, Wattless. Whenever there is a great difference in phase in an alternating current dynamo between volts and current, the true watts are much less than the product of the virtual volts and amperes, because the the watts are obtained by multiplying the product of the virtual volts and amperes by the cosine of the angle of lag (or lead). Any alternating current may be resolved into two components in quadrature with each other, one in phase with the volts, the other in quadrature therewith, the former is termed by S. P. Thompson the Working Current, the latter the Wattless Current. The greater the angle of lag the greater will be the wattless current. Curve, Arrival. A curve representing the rate of rise of intensity of current at the end of a long conductor when the circuit has been closed at the other end. In the Atlantic cable, for instance, it would require about 108 seconds for the current at the distant end to attain 9/10 of its full value. The curve is drawn with its abscissa representing time and its ordinates current strength. Curve, Characteristic. A curve indicating, graphically, the relations between any two factors, which are interdependent, or which vary simultaneously. Thus in a dynamo, the voltage increases with the speed of rotation, and a characteristic curve may be based on the relations between the speed of rotation and voltage developed. The current produced by a dynamo varies with the electro-motive force, and a curve can express the relations between the electro-motive force and the current produced. A characteristic curve is usually laid out by rectangular co-ordinates (see Co-ordinates). Two lines are drawn at right angles to each other, one vertical, and the other horizontal. One set of data are marked off on the horizontal line, say one ampere, two amperes, and so on, in the case of a dynamo's characteristic curve. For each amperage of current there is a corresponding voltage in the circuit. Therefore on each ampere mark a vertical is erected, and on that the voltage corresponding to such amperage is laid off. This gives a series of points, and these points may be connected by a curve. Such curve will be a characteristic curve. The more usual way of laying out a curve is to work directly upon the two axes. On one is laid off the series of values of one set of data; on the other the corresponding series of values of the other dependent data. Vertical lines or ordinates, q. v., are erected on the horizontal line or axis of abscissas at the points laid off; horizontal lines or abscissas, q. v., are drawn from the points laid off on the vertical line or axis of ordinates. The characteristic curve is determined by the intersections of each corresponding pair of abscissa and ordinate. 169 STANDARD ELECTRICAL DICTIONARY. Variations exist in characteristic curve methods. Thus to get the characteristic of a commutator, radial lines may be drawn from a circle representing its perimeter. Such lines may be of length proportional to the voltage developed on the commutator at the points whence the lines start. A cut giving an example of such a curve is given in Fig. 125. (See Curve of Distribution of Potential in Armature.) There is nothing absolute in the use of ordinates or abscissas. They may be interchanged. Ordinarily voltages are laid off as ordinates, but the practise may be reversed. The same liberty holds good for all characteristic curves. Custom, however, should be followed. Synonym--Characteristic. Fig. 120. CHARACTERISTIC CURVE OF A DYNAMO WITH HORSE POWER CURVES. Curve, Characteristic, of Converter. The characteristic curve of the secondary circuit of an alternating current converter. It gives by the usual methods (see Curve, Characteristic,) the relations between the electro-motive force and the current in the secondary circuit at a fixed resistance. If connected in parallel a constant electro-motive force is maintained, and the curve is virtually a straight line. If connected in series an elliptical curve is produced. 170 STANDARD ELECTRICAL DICTIONARY. Curve, Charging. In secondary battery manipulation, a curve indicating the increase of voltage as the charging is prolonged. The rise in voltage with the duration of the charging current is not uniform. In one case, shown in the cut, there was a brief rapid rise of about 0.1 volt; then a long slow rise for 0.15 volt; then a more rapid rise for nearly 0.40 volt, and then the curve became a horizontal line indicating a cessation of increase of voltage. The charging rate should be constant. The horizontal line is laid off in hours, the vertical in volts, so that the time is represented by abscissas and the voltage by ordinates of the curve. Fig. 121. CHARGING CURVE OF A SECONDARY BATTERY. Curve, Discharging. A characteristic curve of a storage battery, indicating the fall in voltage with hours of discharge. The volts may be laid off on the axis of ordinates, and the hours of discharging on the axis of abscissas. To give it meaning the rate of discharge must be constant. Curve, Electro-motive Force. A characteristic curve of a dynamo. It expresses the relation between its entire electromotive force, as calculated by Ohm's Law, and the current intensities corresponding thereto. To obtain the data the dynamo is driven with different resistances in the external circuit and the current is measured for each resistance. This gives the amperes. The total resistance of the circuit, including that of the dynamo, is known. By Ohm's Law the electro-motive force in volts is obtained for each case by multiplying the total resistance of the circuit in ohms by the amperes of current forced through such resistance. Taking the voltages thus calculated for ordinates and the corresponding amperages for abscissas the curve is plotted. An example is shown in the cut. 171 STANDARD ELECTRICAL DICTIONARY. Curve, External Characteristic. A characteristic curve of a dynamo, corresponding to the electro-motive force curve, except that the ordinates represent the voltages of the external circuit, the voltages as taken directly from the terminals of the machine, instead of the total electro-motive force of the circuit. The dynamo is run at constant speed. The resistance of the external circuit is varied. The voltages at the terminals of the machine and the amperages of current corresponding thereto are determined. Using the voltages thus determined as ordinates and the corresponding amperages as abscissas the external characteristic curve is plotted. This curve can be mechanically produced. A pencil may be moved against a constant force by two electro-magnets pulling at right angles to each other. One must be excited by the main current of the machine, the other by a shunt current from the terminals of the machine. The point of the pencil will describe the curve. Fig. 122. CHARACTERISTIC CURVE OF A DYNAMO. Curve, Horse Power. Curves indicating electric horse power. They are laid out with co-ordinates, volts being laid off on the axis of ordinates, and amperes on the axis of abscissas generally. The curves are drawn through points where the product of amperes by volts equals 746. On the same diagram 1, 2, 3 .... and any other horse powers can be plotted if within the limits. See Fig. 120. Curve, Isochasmen. A line drawn on the map of the earth's surface indicating the locus of equal frequency of auroras. 172 STANDARD ELECTRICAL DICTIONARY. Curve, Life. A characteristic curve showing the relations between the durability and conditions affecting the same in any appliance. It is used most for incandescent lamps. The hours of burning before failure give ordinates, and the rates of burning, expressed indirectly in volts or in candle-power, give abscissas. For each voltage or for each candle-power an average duration is deducible from experience, so that two dependent sets of data are obtained for the construction of the curve. Curve, Load. A characteristic curve of a dynamo, expressing the relation between its voltage and the amount of excitation under a definite condition of ampere load, at a constant speed. The ordinates represent voltage, the abscissas ampere turns in the field, and the curves may be constructed for a flow of 0, 50, 100, or .. , or any other number of amperes. Fig. 123. LOAD CURVES. Curve, Magnetization. A characteristic curve of an electromagnet, indicating the relation of magnetization to exciting current. Laying off on the axis of ordinates the quantities of magnetism evoked, and the corresponding strengths of the exciting current on the axis of abscissas, the curve can be plotted. It first rises rapidly, indicating a rapid increase of magnetization, but grows nearly horizontal as the iron becomes more saturated. The effect due to the coils alone, or the effect produced in the absence of iron is a straight line, because air does not change in permeability. Curve of Distribution of Potential in Armature. A characteristic curve indicating the distribution of potential difference between adjoining sections of the commutator of an armature in different positions all around it. The potential differences are taken by a volt-meter or potential galvanometer, connection with the armature being made by two small metal brushes, held at a distance apart equal to the distance from centre to centre of two adjoining commutator bars. The curve is laid out as if by polar co-ordinates extending around the cross-section of the commutator, with the distances from the commutator surface to the curve proportional to the potential differences as determined by shifting the pair of brushes all around the commutator. The above is S. P. Thompson's method. Another method of W. M. Mordey involves the use of a pilot brush. (See Brush, Pilot.) Otherwise the method is in general terms identical with the above. 173 STANDARD ELECTRICAL DICTIONARY. Fig. 124. MAGNETIZATION CURVE. Fig. 125. ARMATURE: CURVE. Fig. 126. DEVELOPMENT OF ARMATURE CURVE. Curve of Dynamo. The characteristic curve of a dynamo. (See Curve, Characteristic.) Curve of Sines. An undulating curve representing wave motion. It is produced by compounding a simple harmonic motion, or a two and fro motion like that of an infinitely long pendulum with a rectilinear motion. Along a horizontal line points may be laid off to represent equal periods of time. Then on each point a perpendicular must be erected. The length of each must be equal to the length of path traversed by the point up to the expiration of each one of the given intervals of time. The abscissas are proportional to the times and the ordinates to the sines of angles proportional to the times. Thus if a circle be drawn upon the line and divided into thirty-two parts of equal angular value, the sines of these angles may be taken as the ordinates and the absolute distance or length of arc of the angle will give the abscissas. Synonyms--Sine Curve--Sinusoidal Curve--Harmonic Curve. Fig. 127. CURVE OF SINES. 174 STANDARD ELECTRICAL DICTIONARY. Curve of Saturation of the Magnetic Circuit. A characteristic curve whose ordinates may represent the number of magnetic lines of force induced in a magnetic circuit, and whose abscissas may represent the ampere turns of excitation or other representative of the inducing force. Curve of Torque. A characteristic curve showing the relations between torque, q. v., and current in a dynamo or motor. Curve, Permeability Temperature. A characteristic curve expressing the changes in permeability of a paramagnetic substance as the temperature changes. The degrees of temperature may be abscissas, and the permeabilities corresponding thereto ordinates of the curve. Cut In. v. To connect any electric appliance, mechanism or conductor, into a circuit. Cut Out. v. The reverse of to cut in; to remove from a circuit any conducting device, and sometimes so arranged as to leave the circuit completed in some other way. Cut Out. An appliance for removing any apparatus from an electric circuit, so that no more current shall pass through such apparatus, and sometimes providing means for closing the circuit so as to leave it complete after the removal of the apparatus. 175 STANDARD ELECTRICAL DICTIONARY. Cut Out, Automatic. (a) A mechanism for automatically shunting an arc or other lamp when it ceases to work properly. It is generally worked by an electro-magnet of high resistance placed in parallel with the arc. If the arc grows too long the magnet attracts its armature, thereby completing a shunt of approximately the resistance of the arc, and which replaces it until the carbons approach again to within a proper distance. Sometimes a strip or wire of fusible metal is arranged in shunt with the arc. When the arc lengthens the current through the wire increases, melts it and a spring is released which acts to complete or close a shunt circuit of approximately arc-resistance. (b) See Safety Device--Safety Fuse. (c) See below. Cut-out, Magnetic. A magnetic cut-out is essentially a coil of wire with attracted core or armature. When the coil is not excited the core, by pressing down a strip of metal or by some analogous arrangement, completes the circuit. When the current exceeds a certain strength the core rises as it is attracted and the circuit is opened. Cut-out, Safety. A block of porcelain or other base carrying a safety fuse, which melts and breaks the circuit before the wire connected to it is dangerously heated. Synonyms--Fuse Block--Safety Catch--Safety Fuse. Cut Out, Wedge. A cut out operated by a wedge. The line terminals consist of a spring bearing against a plate, the circuit being completed through their point of contact. A plug or wedge composed of two metallic faces insulated from each other is adapted to wedge the contact open. Terminals of a loop circuit are connected to the faces of the wedge. Thus on sliding it into place, the loop circuit is brought into series in the main circuit. Synonym--Plug Cut Out--Spring Jack. Cutting of Lines of Force. A field of force is pictured as made up of lines of force; a conductor swept through the field is pictured as cutting these lines. By so doing it produces potential difference or electro-motive force in itself with a current, if the conductor is part of a closed circuit. Cycle of Alternation. A full period of alternation of an alternating current. It begins properly at the zero line, goes to a maximum value in one sense and returns to zero, goes to maximum in the other sense and returns to zero. Cystoscopy. Examination of the human bladder by the introduction of a special incandescent electric lamp. The method is due to Hitze. 176 STANDARD ELECTRICAL DICTIONARY. Damper. (a) A copper frame on which the wire in a galvanometer is sometimes coiled, which acts to damp the oscillations of the needle. (b) A tube of brass or copper placed between the primary and secondary coils of an induction coil. It cuts off induction and diminishes the current and potential of the secondary circuit. On pulling it out, the latter increases. It is used on medical coils to adjust their strength of action. Damping. Preventing the indicator of an instrument from oscillating in virtue of its own inertia or elasticity. In a galvanometer it is defined as resistance to quick vibrations of the needle, in consequence of which it is rapidly brought to rest when deflected (Ayrton). In dead-beat galvanometers (see Galvanometer, Dead-Beat,) damping is desirable in order to bring the needle to rest quickly; in ballistic galvanometers (see Galvanometer, Ballistic,) damping is avoided in order to maintain the principle of the instrument. Damping may be mechanical, the frictional resistance of air to an air-vane, or of a liquid to an immersed diaphragm or loosely fitting piston, being employed. A dash-pot, q. v., is an example of the latter. It may be electro-magnetic. A mass of metal near a swinging magnetic needle tends by induced currents to arrest the oscillations thereof, and is used for this purpose in dead-beat galvanometers. This is termed, sometimes, magnetic friction. The essence of damping is to develop resistance to movement in some ratio proportional to velocity, so that no resistance is offered to the indicator slowly taking its true position. (See Galvanometer, Dead-Beat.) Dash-Pot. A cylinder and piston, the latter loosely fitting or perforated, or some equivalent means being provided to permit movement. The cylinder may contain a liquid such as glycerine, or air only. Thus the piston is perfectly free to move, but any oscillations are damped (see Damping). In some arc lamps the carbon holder is connected to a dash-pot to check too sudden movements of the carbon. The attachment may be either to the piston or to the cylinder. In the Brush lamp the top of the carbon holder forms a cylinder containing glycerine, and in it a loosely fitting piston works. This acts as a dash-pot. Dead Beat. adj. Reaching its reading quickly; applied to instruments having a moving indicator, which normally would oscillate back and forth a number of times before reaching its reading were it not prevented by damping. (See Galvanometer, Aperiodic--Damping.) Dead Earth. A fault in a telegraph line which consists in the wire being thoroughly grounded or connected to the earth. 177 STANDARD ELECTRICAL DICTIONARY. Dead Point of an Alternator. A two-phase alternator of the ordinary type connected as a motor to another alternator cannot start itself, as it has dead points where the relations and polarity of field and armature are such that there is no torque or turning power. Dead-Turns. In the winding of an armature, a given percentage of the turns, it may be 80 per cent., more or less, is assumed to be active; the other 20 per cent. or thereabouts, is called dead-turns. This portion represents the wire on such portions of the armature as comes virtually outside of the magnetic field. They are termed dead, as not concurring to the production of electro-motive force. Dead Wire. (a) The percentage or portion of wire on a dynamo or motor armature that does not concur in the production of electromotive force. The dead-turns, q. v., of a drum armature or the inside wire in a Gramme ring armature are dead wire. (b) A disused and abandoned electric conductor, such as a telegraph wire. (c) A wire in use, but through which, at the time of speaking, no current is passing. Death, Electrical. Death resulting from electricity discharged through the animal system. The exact conditions requisite for fatal results have not been determined. High electro-motive force is absolutely essential; a changing current, pulsatory or alternating, is most fatal, possibly because of the high electro-motive force of a portion of each period. Amperage probably has something to do with it, although the total quantity in coulombs may be very small. As applied to the execution of criminals, the victim is seated in a chair and strapped thereto. One electrode with wet padded surface is placed against his head or some adjacent part. Another electrode is placed against some of the lower parts, and a current from an alternating dynamo passed for 15 seconds or more. The potential difference of the electrodes is given at 1,500 to 2,000 volts, but of course the maximum may be two or three times the measured amount, owing to the character of the current. Decalescence. The converse of recalescence, q. v. When a mass of steel is being heated as it reaches the temperature of recalescence it suddenly absorbs a large amount of heat, apparently growing cooler. Deci. Prefix originally used in the metric system to signify one-tenth of, now extended to general scientific units. Thus decimeter means one-tenth of a meter; decigram, one-tenth of a gram. Declination, Angle of. The angle intercepted between the true meridian and the axis of a magnetic needle at any place. The angle is measured to east or west, starting from the true meridian as zero. 178 STANDARD ELECTRICAL DICTIONARY. Declination of the Magnetic Needle. The deviation of the magnetic needle from the plane of the earth's meridian. It is also called the variation of the compass. (See Magnetic Elements.) Decomposition. The reduction of a compound substance into its constituents, as in chemical analysis. The constituents may themselves be compounds or proximate constituents, or may be elemental or ultimate constituents. Decomposition, Electrolytic. The decomposition or separation of a compound liquid into its constituents by electrolysis. The liquid must be an electrolyte, q. v., and the decomposition proceeds subject to the laws of electrolysis, q. v. See also Electrolytic Analysis. Decrement. When a suspension needle which has been disturbed is oscillating the swings gradually decrease in amplitude if there is any damping, as there always is. The decrement is the ratio of the amplitude of one oscillation to the succeeding one. This ratio is the same for any successive swings. De-energize. To cut off its supply of electric energy from an electric motor, or any device absorbing and worked by electric energy. Deflagration. The explosive or violent volatilizing and dissipating of a substance by heat, violent oxidation and similar means. It may be applied among other things to the destroying of a conductor by an intense current, or the volatilization of any material by the electric arc. Deflecting Field. The field produced in a galvanometer by the current which is being tested, and which field deflects the needle, such deflection being the measure of the current strength. Deflection. In magnetism the movement out of the plane of the magnetic meridian of a magnetic needle, due to disturbance by or attraction towards a mass of iron or another magnet. Deflection Method. The method of electrical measurements in which the deflection of the index of the measuring instrument is used as the measure of the current or other element under examination. It is the opposite of and is to be distinguished from the zero or null method, q. v. In the latter conditions are established which make the index point to zero and from the conditions necessary for this the measurement is deduced. The Wheatstone Bridge, q. v., illustrates a zero method, the sine or the tangent compass, illustrates a deflection method. The use of deflection methods involves calibration, q. v., and the commercial measuring instruments, such as ammeters and volt meters, which are frequently calibrated galvanometers, are also examples of deflection instruments. 179 STANDARD ELECTRICAL DICTIONARY. Degeneration, Reaction of. The diminished sensibility to electro-therapeutic treatment exhibited by the human system with continuance of the treatment in question. The general lines of variation are stated in works on the subject. Deka. Prefix originally used in the metric system to signify multiplying by ten, as dekameter, ten meters, dekagram, ten grams; now extended to many scientific terms. De la Rive's Floating Battery. A small galvanic couple, immersed in a little floating cell and connected through a coil of wire immediately above them. When the exciting battery solution is placed in the cell the whole, as it floats in a larger vessel, turns until the coil lies at right angles to the magnetic needle. Sometimes the two plates are thrust through a cork and floated thus in a vessel of dilute sulphuric acid. A magnet acts to attract or repel the coil in obedience to Ampére's Theory, (See Magnetism, Ampere's Theory of.) Delaurier's Solution. A solution for batteries of the Bunsen and Grenet type. It is of the following composition: Water, 2,000 parts; potassium bichromate, 184 parts; sulphuric acid, 428 parts. Demagnetization. Removal of magnetism from a paramagnetic substance. It is principally used for watches which have become magnetized by exposure to the magnetic field surrounding dynamos or motors. The general principles of most methods are to rotate the object, as a watch, in a strong field, and while it is rotating to gradually remove it from the field, or to gradually reduce the intensity of the field itself to zero. A conical coil of wire within which the field is produced in which the watch is placed is sometimes used, the idea being that the field within such a coil is strongest at its base. Such a coil supplied by an alternating current is found effectual (J. J. Wright). If a magnetized watch is made to turn rapidly at the end of a twisted string and is gradually brought near to and withdrawn from the poles of a powerful dynamo it may be considerably improved. A hollow coil of wire connected with a pole changer and dip-battery has been used. The battery creates a strong field within the coil. The watch is placed there and the pole changer is worked so as to reverse the polarity of the field very frequently. By the same action of the pole changer the plates of the battery are gradually withdrawn from the solution so as to gradually reduce the magnetic field to zero while constantly reversing its polarity. (G. M. Hopkins.) Steel may be demagnetized by jarring when held out of the magnetic meridian, or by heating to redness. 180 STANDARD ELECTRICAL DICTIONARY. Density, Electric Superficial. The relative quantity of electricity residing as an electric charge upon a unit area of surface. It may be positive or negative. Synonyms--Density of Charge--Surface Density. Dental Mallet, Electric. A dentist's instrument for hammering the fillings as inserted into teeth. It is a little hammer held in a suitable handle, and which is made to strike a rapid succession of blows by electro-magnetic motor mechanism. Depolarization. (a) The removal of permanent magnetism. (See Demagnetization.) (b) The prevention of the polarization of a galvanic cell. It is effected in the Grove battery by the reduction of nitric acid; in the Bunsen, by the reduction of chromic acid; in the Smee battery, mechanically, by the platinum coated or rather platinized negative plate. Other examples will be found under the description of various cells and batteries. A fluid which depolarizes is termed a depolarizer or depolarizing fluid or solution. (See Electropoion Fluid.) Deposit, Electrolytic. The metal or other substance precipitated by the action of a battery or other current generator. Derivation, Point of. A point where a circuit branches or divides into two or more leads. The separate branches then receive derived or partial currents. Desk Push. A press or push button, with small flush rim, for setting into the woodwork of a desk. Detector. A portable galvanometer, often of simple construction, used for rough or approximate work. Detector, Lineman's. A portable galvanometer with a high and a low resistance actuating coil, constructed for the use of linemen and telegraph constructors when in the field, and actually putting up, repairing or testing lines. Deviation, Quadrantal. Deviation of the compass in iron or steel ships due to the magnetization of horizontal beams by the earth's induction. The effect of this deviation disappears when the ship is in the plane of the electric meridian, or at right angles thereto; its name is taken from the fact that a swing of the ship through a quadrant brings the needle from zero deviation to a maximum and back to zero. 181 STANDARD ELECTRICAL DICTIONARY. Deviation, Semicircular. Deviation of the compass in iron or steel ships due to vertical induction. (See Induction, Vertical.) The effect of this induction disappears when the ship is in the electric meridian. Its name is derived from the fact that a swing of the ship through half the circle brings the needle from zero deviation to a maximum and back to zero. Dextrotorsal. adj. Wound in the direction or sense of a right-handed screw; the reverse of sinistrotorsal, q. v. Fig. 128. DEXTROTORSAL HELIX. Diacritical. adj. (a) The number of ampere turns, q. v., required to bring an iron core to one half its magnetic saturation, q. v., is termed the diacritical number. (b) The diacritical point of magnetic saturation is proposed by Sylvanus P. Thompson as a term for the coefficient of magnetic saturation which gives a magnet core one-half its maximum magnetization. Diagnosis, Electro. A medical diagnosis of a patient's condition based on the action of different parts of the body under electric excitement. Diamagnetic. adj. Possessing a negative coefficient of magnetic susceptibility; having permeability inferior to that of air. Such substances placed between the poles of a magnet are repelled; if in the form of bars, they tend to turn so as to have their long axis at right angles to the line joining the poles. The reason is that the lines of force always seek the easiest path, and these bodies having higher reluctance than air, impede the lines of force, and hence are as far as possible pushed out of the way. The above is the simplest explanation of a not well understood set of phenomena. According to Tyndall, "the diamagnetic force is a polar force, the polarity of diamagnetic bodies being opposed to that of paramagnetic ones under the same conditions of excitement." Bismuth is the most strongly diamagnetic body known; phosphorus, antimony, zinc, and many others are diamagnetic. (See Paramagnetic.) 182 STANDARD ELECTRICAL DICTIONARY. Diagometer. An apparatus for use in chemical analysis for testing the purity of substances by the time required for a charged surface to be discharged through them to earth. It is the invention of Rousseau. An electrometer is charged with a dry pile. One of its terminals is connected with one surface of the solution or substance to be tested, and the other with the other surface. The time of discharge gives the index of the purity of the substance. Diamagnetic Polarity. Treating diamagnetism as due to a polar force, the polarity of a diamagnetic body is the reverse of the polarity of iron or other paramagnetic bodies. A bar-shaped diamagnetic body in a field of force tends to place itself at right angles to the lines of force. Diamagnetism. (a) The science or study of diamagnetic substances and phenomena. (b) The magnetic property of a diamagnetic substance. Diameter of Commutation. The points on the commutator of a closed circuit ring--or drum--armature, which the brushes touch, and whence they take the current, mark the extremities of the diameter of commutation. Were it not for the lag this would be the diameter at right angles to the line connecting the centers of the opposite faces of the field. It is always a little to one side of this position, being displaced in the direction of rotation. In open circuit armatures the brushes are placed on the diameter at right angles to this one, and sometimes the term diameter of commutation is applied to it. All that has been said is on the supposition that the armature divisions correspond not only in connection but in position with those of the armature coils. Of course, the commutator could be twisted so as to bring the diameter of commutation into any position desired. Diapason, Electric. A tuning-fork or diapason kept in vibration by electricity. In general principle the ends of the fork act as armatures for an electro-magnet, and in their motion by a mercury cup or other form of contact they make and break the circuit as they vibrate. Thus the magnet alternately attracts and releases the leg, in exact harmony with its natural period of vibration. Diaphragm. (a) In telephones and microphones a disc of iron thrown into motion by sound waves or by electric impulses, according to whether it acts as the diaphragm of a transmitter or receiver. It is generally a plate of japanned iron such as used in making ferrotype photographs. (See Telephone and Microphone.) (b) A porous diaphragm is often used in electric decomposition cells and in batteries. The porous cup represents the latter use. [Transcriber's note: Japanned--covered with heavy black lacquer, like enamel paint.] 183 STANDARD ELECTRICAL DICTIONARY. Dielectric. A non-conductor; a substance, the different parts of which may, after an electric disturbance, remain, without any process of readjustment, and for an indefinite period of time, at potentials differing to any extent (Daniell). There is no perfect dielectric. The term dielectric is generally only used when an insulator acts to permit induction to take place through it, like the glass of a Leyden jar. Dielectric Constant. The number or coefficient expressing the relative dielectric capacity of a medium or substance. (See Capacity, Specific Inductive.) Dielectric, Energy of. In a condenser, the conducting coatings are merely to conduct the current all over the surface they cover; the keeping the electricities separated is the work of the dielectric, and represents potential energy which appears in the discharge. The amount of energy is proportional to the charge, and to the potential difference. As any electrified body implies an opposite electrification somewhere, and a separating dielectric, the existence of a condenser is always implied. [Transcriber's note: The energy stored in a capacitor (condenser) is (Q*Q)/2C = (Q*V)/2 = (C*V*V)/2 The energy is proportional to the voltage SQUARED or the charge SQUARED.] Dielectric Polarization. A term due to Faraday. It expresses what he conceived to be the condition of a dielectric when its opposite faces are oppositely electrified. The molecules are supposed to be arranged by the electrification in a series of polar chains, possibly being originally in themselves seats of opposite polarities, or having such imparted to them by the electricities. The action is analogous to that of a magnet pole on a mass of soft iron, or on a pile of iron filings. Dielectric Strain. The strain a solid dielectric is subjected to, when its opposite surfaces are electrified. A Leyden jar dilates under the strain, and when discharged gives a dull sound. The original condition is not immediately recovered. Jarring, shaking, etc., assist the recovery from strain. The cause of the strain is termed Electric Stress. (See Stress, Electric.) This is identical with the phenomenon of residual charge. (See Charge, Residual.) Each loss of charge is accompanied with a proportional return of the dielectric towards its normal condition. Dielectric Resistance. The mechanical resistance a body offers to perforation or destruction by the electric discharge. Dielectric Strength. The resistance to the disruptive discharge and depending on its mechanical resistance largely or entirely. It is expressible in volts per centimeter thickness. Dry air requires 40,000 volts per centimeter for a discharge. 184 STANDARD ELECTRICAL DICTIONARY. Differential Winding Working. A method of working an electro-magnet intermittently, so as to avoid sparking. The magnet is wound with two coils. One is connected straight into the circuit, the other is connected in parallel therewith with a switch inserted. The coils are so connected that when the switch is closed the two are in opposition, the current going through them in opposite senses. Thus one overcomes the effect of the other and the magnet core shows no magnetism, provided the two coils are of equal resistance and equal number of convolutions or turns. Fig. 129. DIFFERENTIAL WINDING WORKING OF ELECTRO-MAGNETIC APPARATUS. Diffusion. A term properly applied to the varying current density found in conductors of unequal cross sectional area. In electro-therapeutics it is applied to the distribution of current as it passes through the human body. Its density per cross-sectional area varies with the area and with the other factors. Diffusion Creep. When electrodes of an active circuit are immersed in a solution of an electrolyte, a current passes electrolytically if there is a sufficient potential difference. The current passes through all parts of the solution, spreading out of the direct prism connecting or defined by the electrodes. To this portion of the current the above term is applied. If the electrodes are small enough in proportion to the distance between them the current transmission or creep outside of the line becomes the principal conveyor of the current so that the resistance remains the same for all distances. Dimensions and Theory of Dimensions. The expression of the unitary value of a physical quantity in one or more of the units of length (L), time (T) and mass (M) is termed the dimensions of such quantity. Thus the dimension or dimensions of a distance is simply L; of an angle, expressible by dividing the arc by the radius is L/L; of a velocity, expressible by distance divided by time--L/T; of acceleration, which is velocity acquired in a unit of time, and is therefore expressible by velocity divided by time--L/T/T or L/T2; of momentum, which is the product of mass into velocity--M*L/T; of kinetic energy taken as the product of mass into the square of velocity--M*(L2/T2); of potential energy taken as the product of mass into acceleration into space-M*(L/T2)*L reducing to M*(L2/T2). The theory is based on three fundamental units and embraces all electric quantities. The simple units generally taken are the gram, centimeter and second and the dimensions of the fundamental compound units are expressed in terms of these three, forming the centimeter-gram-second or C. G. S. system of units. Unless otherwise expressed or implied the letters L, M and T, may be taken to indicate centimeter, gram and second respectively. It is obvious that very complicated expressions of dimensions may be built up, and that a mathematical expression of unnamed quantities may be arrived at. Dimensions in their application by these symbols are subject to the laws of algebra. They were invented by Fourier and were brought into prominence by J. Clerk Maxwell. Another excellent definition reads as follows: "By the dimensions of a physical quantity we mean the quantities and powers of quantities, involved in the measurement of it." (W. T. A. Emtage.) 185 STANDARD ELECTRICAL DICTIONARY. Dimmer. An adjustable choking coil used for regulating the intensity of electric incandescent lights. Some operate by the introduction and withdrawal of an iron core as described for the choking coil (see Coil, Choking), others by a damper of copper, often a copper ring surrounding the coil and which by moving on or off the coil changes the potential of the secondary circuit. Dip of Magnetic Needle. The inclination of the magnetic needle. (See Elements, Magnetic.) Dipping. (a) Acid or other cleaning processes applied by dipping metals in cleaning or pickling solutions before plating in the electroplater's bath. (b) Plating by dipping applies to electroplating without a battery by simple immersion. Copper is deposited on iron from a solution of copper sulphate in this way. Synonym--Simple Immersion. Dipping Needle. A magnet mounted in horizontal bearings at its centre of gravity. Placed in the magnetic meridian it takes the direction of the magnetic lines of force of the earth at that point. It is acted on by the vertical component of the earth's magnetism, as it has no freedom of horizontal movement. (See Magnetic Elements, and Compass, Inclination.) Directing Magnet. In a reflecting galvanometer the magnet used for controlling the magnetic needle by establishing a field. It is mounted on the spindle of the instrument above the coil and needle. Synonym--Controlling Magnet. 186 STANDARD ELECTRICAL DICTIONARY. Direction. (a) The direction of an electric current is assumed to be from a positively charged electrode or terminal to a negatively charged one in the outer circuit. (See Current.) (b) The direction of magnetic and electro-magnetic lines of force is assumed to be from north to south pole of a magnet in the outer circuit. It is sometimes called the positive direction. Their general course is shown in the cuts diagrammatically. The circles indicate a compass used in tracing their course. The magnetic needle tends to place itself in the direction of or tangential to the lines of force passing nearest it. (c) The direction of electrostatic lines of force is assumed to be out of a positively charged and to a negatively charged surface. Fig. 130. DIRECTION OF LINES OF FORCE OF A PERMANENT MAGNET. Fig. 131, DIRECTION OF LINES OF FORCE OF AN ELECTRO-MAGNET. 187 STANDARD ELECTRICAL DICTIONARY. Directive Power. In magnetism the power of maintaining itself in the plane of the magnetic meridian, possessed by the magnetic needle. Discharge, Brush. The static discharge of electricity into or through the air may be of the brush or spark form. The brush indicates the escape of electricity in continuous flow; the spark indicates discontinuity. The conditions necessary to the production of one or the other refer to the nature of the conductor, and of other conductors in its vicinity and to the electro-motive force or potential difference; small alterations may transform one into the other. The brush resembles a luminous core whose apex touches the conductor. It is accompanied by a slight hissing noise. Its luminosity is very feeble. The negative conductor gives a smaller brush than that of the positive conductor and discharges it more readily. When electricity issues from a conductor, remote from an oppositely excited one, it gives an absolutely silent discharge, showing at the point of escape a pale blue luminosity called electric glow, or if it escapes from points it shows a star-like centre of light. It can be seen in the dark by placing a point on the excited conductor of a static-electric machine. Synonyms--Silent Discharge--Glow Discharge. Discharge, Conductive. A discharge of a static charge by conduction through a conductor. Discharge, Convective. The discharge of static electricity from an excited conductor through air or rarefied gas; it is also called the quiet or silent discharge. The luminous effect in air or gas at atmospheric pressures takes the form of a little brush from a small positive electrode; the negative shows a star. The phenomena of Gassiot's cascade, the philosopher's egg and Geissler tubes, all of which may be referred to, are instances of convective discharge. Discharge, Dead Beat. A discharge that is not oscillatory in character. Discharge, Disruptive. A discharge of a static charge through a dielectric. It involves mechanical perforation of the dielectric, and hence the mere mechanical strength of the latter has much to do with preventing it. A disruptive discharge is often oscillatory in character; this is always the case with the discharge of a Leyden jar. 188 STANDARD ELECTRICAL DICTIONARY. Discharge, Duration of. The problem of determining this factor has been attacked by various observers. Wheatstone with his revolving mirror found it to be 1/24000 second. Fedderson, by interposing resistance, prolonged it to 14/10000 and again to 138/10000 second. Lucas & Cazin made it from 26 to 47 millionths of a second. All these experiments were performed with Leyden jars. Discharge, Impulsive. A disruptive discharge produced between conductors by suddenly produced potential differences. The self-induction of the conductor plays an especially important part in discharges thus produced. Discharge, Lateral. (a) A lightning discharge, which sometimes takes place between a lightning rod and the building on which it is. (b) In the discharge of a Leyden jar or condenser the discharge which takes the alternative path, q. v. Discharge, Oscillatory. The sudden or disruptive discharge of a static condenser, such as a Leyden jar, or of many other charged conductors, is oscillatory in character. The direction of the currents rapidly changes, so that the discharge is really an alternating current of excessively short total duration. The discharge sends electro-magnetic waves through the ether, which are exactly analogous to those of light but of too long period to affect the eye. Synonym--Surging Discharge. [Transcriber's note: Marconi's transmission across the English channel occurs in 1897, five years after the publication of this book.] Fig. 132. DISCHARGER. Discharger. An apparatus for discharging Leyden jars. It consists of a conductor terminating in balls, and either jointed like a tongs or bent with a spring-action, so that the balls can be set at distances adapted to different sized jars. It has an insulating handle or a pair of such. In use one ball is brought near to the coating and the other to the spindle ball of the jar. When nearly or quite in contact the jar discharges. Synonyms--Discharging Rod--Discharging Tongs. 189 STANDARD ELECTRICAL DICTIONARY. Discharger, Universal. An apparatus for exposing substances to the static discharge spark. It consists of a base with three insulating posts. The central post carries an ivory table to support the object. The two side posts carry conducting rods, terminating in metal balls, and mounted with universal joints. A violent shock can be given to any object placed on the table. Synonym--Henley's Universal Discharger. Discharge, Silent. This term is sometimes applied to the glow or brush discharge and sometimes to the condition of electric effluvium. (See Discharge, Brush--Effluvium, Electric.) Discharge, Spark. The discontinuous discharge of high tension electricity through a dielectric or into the air produces electric sparks. These are quite strongly luminous, of branching sinuous shape, and in long sparks the luminosity varies in different parts of the same spark. A sharp noise accompanies each spark. High density of charge is requisite for the formation of long sparks. Disconnection. The separation of two parts of, or opening a circuit, as by turning a switch, unscrewing a binding screw, or the like. The term is sometimes used to indicate a class of faults in telegraph circuits. Disconnections may be total, partial or intermittent, and due to many causes, such as open or partially replaced switches, oxidized or dirty contact points, or loose joints. Displacement, Electric. A conception of the action of charging a dielectric. The charge is all on the surface. This fact being granted, the theory of displacement holds that charging a body is the displacing of electricity, forcing it from the interior on to the surface, or vice versa, producing a positive or negative charge by displacement of electricity. While displacement is taking place in a dielectric there is assumed to be a movement or current of electricity called a displacement current. Disruptive Tension. When the surface of a body is electrified, it tends to expand, all portions of the surface repelling each other. The film of air surrounding such a body is electrified too, and is subjected to a disruptive tension, varying in intensity with the square of the density. Dissimulated Electricity. The electricity of a bound charge. (See Charge, Bound.) Dissociation. The separation of a chemical compound into its elements by a sufficiently high degree of heat. All compounds are susceptible of dissociation, so that it follows that combustion is impossible at high temperatures. 190 STANDARD ELECTRICAL DICTIONARY. Distance, Critical, of Alternative Path. The length of air gap in an alternative path whose resistance joined to the impedance of the rest of the conductors of the path just balances the impedance of the other path. Distance, Sparking. The distance between electrodes, which a spark from a given Leyden jar or other source will pass across. Synonym--Explosive Distance. Distillation. The evaporation of a liquid by heat, and sometimes in a vacuum, followed by condensation of the vapors, which distil or drop from the end of the condenser. It is claimed that the process is accelerated by the liquid being electrified. Distributing Box. In an electric conduit system, a small iron box provided for giving access to the cable for the purpose of making house and minor connections. Synonym--Hand Hole. Distributing Switches. Switch systems for enabling different dynamos to supply different lines of a system as required. Spring jacks, q. v., are used for the lines, and plug switches for the dynamo leads. Thus, dynamos can be thrown in or out as desired, without putting out the lights. Distribution of Electric Energy, Systems of. The systems of electric current distribution from central stations or from private generating plants, mechanical or battery, the latter primary or secondary. They include in general the alternating current system and direct current systems. Again, these may be subdivided into series and multiple arc, multiple-series and series-multiple distribution, and the three, four, or five wire system may be applied to multiple arc or multiple series systems. (See Alternating Current--Current System--Multiple Arc--Multiple Series--Series Multiple--Three Wire System.) Door Opener, Electric. An apparatus for opening a door by pushing back the latch. A spring then draws the door open, and it is closed against the force of the spring by the person entering. Electro-magnetic mechanism actuates the latch, and is operated by a switch or press-button. Thus a person on the upper floor can open the hall door without descending. Dosage, Galvanic. In electro-therapeutics the amount of electric current or discharge, and duration of treatment given to patients. Double Carbon Arc Lamp. An arc lamp designed to burn all night, usually constructed with two parallel sets of carbons, one set replacing the other automatically, the current being switched from the burnt out pair to the other by the action of the mechanism of the lamp. 191 STANDARD ELECTRICAL DICTIONARY. Double Fluid Theory. A theory of electricity. Electricity is conveniently treated as a fluid or fluids. According to the double fluid hypothesis negative electricity is due to a preponderance of negative fluid and vice versa. Like fluid repels like, and unlike attracts unlike; either fluid is attracted by matter; the presence in a body of one or the other induces electrification; united in equal proportions they neutralize each other, and friction, chemical decomposition and other causes effect their separation. The hypothesis, while convenient, is overshadowed by the certainty that electricity is not really a fluid at all. (See Single Fluid Theory--Fluid, Electric.) Synonym--Symmer's Theory. [Transcriber's note: Current is the motion of negative electrons in a conductor or plasma. Unequal distribution of electrons is static electricity. The relatively immobile nuclei of atoms are positive when one or more of its electrons is absent and accounts for part of the current in electrolysis and plasmas.] Double Fluid Voltaic Cell. A cell in which two fluids are used, one generally as depolarizer surrounding the negative plate, the other as excitant surrounding the positive plate. A porous diaphragm or difference in specific gravities is used to keep the solutions separate and yet permit the essential electrolytic diffusion. Grove's Cell, Bunsen's Cell, and Daniell's Cell, all of which may be referred to, are of this type, as are many others. Double Wedge. A plug for use with a spring-jack. It has connection strips at its end and another pair a little distance back therefrom, so that it can make two loop connections at once. Synonym--Double Plug. Doubler. A continuously acting electrophorous, q.v.; an early predecessor of the modern electric machines. It is now no longer used. D. P. Abbreviation for Potential Difference. Drag. The pull exercised by a magnetic field upon a conductor moving through it or upon the motion of an armature in it. Dreh-strom. (German) Rotatory currents; a system of currents alternating in periodic succession of phases and producing a rotatory field. (See Field, Rotatory--Multiphase Currents.) Drill Electric. A drill for metals or rock worked by an electro-magnetic motor. For metals a rotary motion, for rocks a reciprocating or percussion action is imparted. It is used by shipbuilders for drilling holes in plates which are in place in ships, as its flexible conductors enable it to be placed anywhere. For rock-drilling a solenoid type of construction is adopted, producing rapid percussion. 192 STANDARD ELECTRICAL DICTIONARY. Drip Loop. A looping downward of wires entering a building, so that rain water, as it runs along the wire, will drip from the lowest part of the loop instead of following the wire into or against the side of the building. Driving Horns. Projections on the periphery of an armature of a dynamo for holding the winding in place and preventing its displacement. Various arrangements have been adopted. They are sometimes wedges or pins and are sometimes driven into spaces left in the drum core. The toothed disc armature cores make up an armature in which the ridges formed by the teeth form practically driving horns. Dronier's Salt. A substance for solution for use in bichromate batteries. It is a mixture of one-third potassium bichromate and two-thirds potassium bisulphate. It is dissolved in water to make the exciting fluid. Drop, Automatic. A switch or circuit breaker, operating to close a circuit by dropping under the influence of gravity. It is held up by a latch, the circuit remaining open, until the latch is released by a current passing through an electro-magnet. This attracting an armature lets the drop fall. As it falls it closes a local or second circuit, and thus may keep a bell ringing until it is replaced by hand. It is used in burglar alarms, its function being to keep a bell ringing even though the windows or door by which entrance was made is reclosed. 193 STANDARD ELECTRICAL DICTIONARY. Fig. 133. THE MAGIC DRUM. Drum, Electric. A drum with a mechanism within for striking the head with a hammer or some equivalent method so as to be used as a piece of magical apparatus. In the one shown in the cut a sort of telephone action is used to produce the sound, the electro-magnet D and armature being quite screened from observation through the hole. (See Fig. 133) A ring, C, shown in Fig. 133, with two terminals, the latter shown by the unshaded portions a a, and a suspending hook E, also with two terminals, and two suspending conductors A, B, carry the current to the magnet. A sudden opening or closing of the circuit produces a sound. Dub's Laws. 1. The magnetism excited at any transverse section of a magnet is proportional to the square root of the distance between the given section and the end. 2. The free magnetism at any given transverse section of a magnet is proportional to the difference between the square root of half the length of the magnet and the square root of the distance between the given section and the nearest end. Duct. The tube or compartment in an electric subway for the reception of a cable. (See Conduit, Electric Subway.) Dyad. A chemical term; an element which in combination replaces two monovalent elements; one which has two bonds or is bivalent. Dyeing, Electric. The producing mordanting or other dyeing effects on goods in dyeing by the passage of an electric current. Dynamic Electricity. Electricity of relatively low potential and large quantity; current electricity as distinguished from static electricity; electricity in motion. 194 STANDARD ELECTRICAL DICTIONARY. Dynamo, Alternating Current. A dynamo-electric machine for producing an alternating current; an alternator. They are classified by S. P. Thompson into three classes--I. Those with stationary field-magnet and rotating armature. II. Those with rotating field magnet and stationary armature. III. Those with both field magnet part and armature part stationary, the amount of magnetic induction from the latter through the former being caused to vary or alternate in direction by the revolution of appropriate pieces of iron, called inductors. Another division rests on whether they give one simple alternating current, a two phase current, or whether they give multi phase currents. (See Current, Alternating--Currents, Multiphase.) A great many kinds of alternators have been constructed. Only an outline of the general theory can be given here. They are generally multipolar, with north and south poles alternating around the field. The armature coils, equal in number in simple current machines, to the poles, are wound in opposite senses, so that the current shall be in one direction, though in opposite senses, in all of them at anyone time. As the armature rotates the coils are all approaching their poles at one time and a current in one sense is induced in every second coil, and one in the other sense in the other coils. They are all in continuous circuit with two open terminals, each connected to its own insulated connecting ring on the shaft. As the coils pass the poles and begin to recede from them the direction changes, and the current goes in the other direction until the next poles are reached and passed. Thus there are as many changes of direction of current per rotation as there are coils in the armature or poles in the field. Fig. 134. ALTERNATING CURRENT DYNAMO WITH SEPARATE EXCITER MOUNTED ON MAIN SHAFT. 195 STANDARD ELECTRICAL DICTIONARY. The field-magnets whose windings may be in series are often excited by a separate direct current generation. Some are self-exciting, one or more of the armature coils being separated from the rest, and connected to a special commutator, which rectifies its current. By properly spacing the coils with respect to the poles of the field, and connecting each set of coils by itself to separate connecting rings, several currents can be taken from the same machine, which currents shall have a constant difference in phase. It would seem at first sight that the same result could be attained by using as many separate alternators as there were currents to be produced. But it would be almost impossible to preserve the exact relation of currents and current phase where each was produced by its own machine. The currents would overrun each other or would lag behind. In a single machine with separate sets of coils the relation is fixed and invariable. Fig. I35. DIAGRAM OF ARRANGEMENT OF ARMATURE COILS AND COLLECTING RINGS IN AN ALTERNATING CURRENT DYNAMO. Dynamo, Alternating Current, Regulation of. Transformers, converters, or induction coils are used to regulate alternating current dynamos, somewhat as compound winding is applied in the case of direct-current dynamos. The arrangement consists in connecting the primary of an induction coil or transformer into the external circuit with its secondary connected to the field circuit. Thus the transformer conveys current to the field picked up from the main circuit, and represents to some extent the shunt of a direct-current machine. Dynamo, Commercial Efficiency of. The coefficient, q. v., obtained by dividing the mechanically useful or available work of a dynamo by the mechanical energy absorbed by it. This only includes the energy available in the outer circuit, for doing useful work. 196 STANDARD ELECTRICAL DICTIONARY. Fig. 136. COMPOUND WOUND DYNAMO. Dynamo. Compound. A compound wound dynamo; one which has two coils on its field magnet; one winding is in series with the external circuit and armature; the other winding is in parallel with the armature winding, or else with the armature winding and field winding, both in series. (See Winding, Long Shunt--Winding, Short Shunt.) Such a dynamo is, to a certain extent, self-regulating, the two coils counteracting each other, and bringing about a more regular action for varying currents than that of the ordinary shunt or series dynamo. The extent of the regulation of such a machine depends on the proportions given its different parts. However good the self-regulating may be in a compound wound machine, it can only be perfect at one particular speed. To illustrate the principle on which the approximate regulation is obtained the characteristic curve diagram may be consulted. Fig. 137. CURVES OF SERIES AND SHUNT WINDINGS SUPERIMPOSED. One curve is the curve of a series winding, the other that of a shunt winding, and shows the variation of voltage in each with resistance in the external or working circuit. The variation is opposite in each case. It is evident that the two windings could be so proportioned on a compound machine that the resultant of the two curves would be a straight line. This regulation would then be perfect and automatic, but only for the one speed. 197 STANDARD ELECTRICAL DICTIONARY. Dynamo, Direct Current. A dynamo giving a current of unvarying direction, as distinguished from an alternator or alternating current dynamo. Dynamo, Disc. A dynamo with a disc armature, such as Pacinotti's disc, q. v. (See also Disc, Armature.) The field magnets are disposed so that the disc rotates close to their poles, and the poles face or are opposite to the side or sides of the disc. The active leads of wire are those situated on the face or faces of the disc. Fig. 138. POLECHKO'S DISC DYNAMO. Dynamo-electric Machine. A machine driven by power, generally steam power, and converting the mechanical energy expended on driving it into electrical energy of the current form. The parts of the ordinary dynamo may be summarized as follows: First, A circuit as complete as possible of iron. Such circuit is composed partly of the cores of an electro-magnet or of several electro-magnets, and partly of the cylindrical or ring-shaped core of an armature which fits as closely as practicable between the magnet ends or poles which are shaped so as to partly embrace it. Second, of coils of insulated wire wound upon the field-magnet cores. When these coils are excited the field-magnets develop polarity and the circuit just spoken of becomes a magnetic circuit, interrupted only by the air gaps between the poles and armatures. Thirdly, of coils of insulated wire upon the armature core. These coils when rotated in the magnetic field cut magnetic lines of force and develop electro-motive force. 198 STANDARD ELECTRICAL DICTIONARY. Fourthly, of collecting mechanism, the commutator in direct current dynamos, attached to the armature shaft and rotating with it. This consists of insulated rings, or segments of rings to which the wire coils of the armature are connected, and on which two springs of copper or plates of carbon or some other conductor presses. The electro-motive force developed by the cutting of lines of force, by the wires of the armature, shows itself as potential difference between the two springs. If the ends of a conductor are attached, one to each of these brushes, the potential difference will establish a current through the wire. By using properly divided and connected segments on the commutator the potential difference and consequent direction of the current may be kept always in the same sense or direction. It is now clear that the external wire may be connected with the windings of the field-magnet. In such case the excitement of the field-magnets is derived from the armature and the machine is self-excited and entirely self-contained. The above is a general description of a dynamo. Sometimes the coils of the field-magnets are not connected with the armature, but derive their current from an outside source. Such are termed separately excited dynamos. Some general features of dynamo generators may be seen in the definitions under this head and elsewhere. The general conception is to cut lines of force with a conductor and thus generate electromotive force, or in some way to change the number of lines of force within a loop or circuit with the same effect. Dynamo, Electroplating. A dynamo designed for low potential and high current intensity. They are wound for low resistance, frequently several wires being used in parallel, or ribbon, bar or rectangular conductors being employed. They are of the direct current type. They should be shunt wound or they are liable to reverse. They are sometimes provided with resistance in the shunt, which is changed as desired to alter the electro-motive force. Dynamo, Equalizing. A combination for three and five-wire systems. A number of armatures or of windings on the same shaft are connected across the leads. If the potential drops at any pair of mains, the armature will begin to be driven by the other mains, acting to an extent as an element of a motor, and will raise the potential in the first pair. Dynamo, Far Leading. A motor dynamo, used to compensate the drop of potential in long mains. Into the mains at a distant point a series motor is connected, driving a dynamo placed in shunt across the mains. The dynamo thus driven raises the potential difference between the two mains. 199 STANDARD ELECTRICAL DICTIONARY. Dynamograph. A printing telegraph in which the message is printed at both transmitting and receiving ends. Dynamo, Inductor. A generator in which the armature or current-generating windings are all comprised upon the poles of the field magnets. Masses of iron, which should be laminated and are the inductors, are carried past the field magnet poles concentrating in their passage the lines of force, thus inducing currents in the coils. In one construction shown in the cut the field magnets a, a .. are U shaped and are arranged in a circle, their poles pointing inwards. A single exciting coil c, c ... is wound around the circle in the bend of the V-shaped segments. The poles carry the armature coils e, e ... The laminated inductors i, i ... are mounted on a shaft S, by spiders h, to be rotated inside the circle of magnets, thus generating an alternating current. Synonym--Inductor Generator. Fig. 139. INDUCTOR DYNAMO. Dynamo, Interior Pole. A dynamo with a ring armature, with field magnet pole pieces which extend within the ring. 200 STANDARD ELECTRICAL DICTIONARY. Dynamo, Iron Clad. A dynamo in which the iron of the field magnet is of such shape as to enclose the field magnet coils as well as the armature. Dynamometer. A device or apparatus for measuring force applied, or rate of expenditure of energy by, or work done in a given time by a machine. A common spring balance can be used as a force dynamometer, viz: to determine how hard a man is pulling and the like. The steam engine indicator represents an energy-dynamometer of the graphic type, the instrument marking an area whence, with the aid of the fixed factors of the engine, the work done may be determined. Prony's Brake, q. v., is a type of the friction dynamometer, also of the energy type. In the latter type during the experiment the whole power must be turned on or be expended on the dynamometer. Dynamo, Motor. A motor dynamo is a machine for (a) converting a continuous current at any voltage to a continuous current of different strength at a different voltage or for (b) transforming a continuous current into an alternating one, and vice versa. For the first type see Transformer, Continuous Current; for the second type see Transformer, Alternating Current. Dynamo, Multipolar. A dynamo having a number of field magnet poles, not merely a single north and a single south pole. The field magnet is sometimes of a generally circular shape with the poles arranged radially within it, the armature revolving between the ends. Dynamo, Non-polar. A name given by Prof. George Forbes to a dynamo invented by him. In it a cylinder of iron rotates within a perfectly self-contained iron-clad field magnet. The current is taken off by brushes bearing near the periphery, at two extremities of a diameter. A machine with a disc 18 inches in diameter was said to give 3,117 amperes, with 5.8 volts E. M. F. running at 1,500 revolutions per second. The E. M. F. of such machines varies with the square of the diameter of the disc or cylinder. Dynamo, Open Coil. A dynamo the windings of whose armatures may be grouped in coils, which are not connected in series, but which have independent terminals. These terminals are separate divisions of the commutator and so spaced that the collecting brushes touch each pair belonging to the same coil simultaneously. As the brushes come in contact with the sections forming the terminals they take current from the coil in question. This coil is next succeeded by another one, and so on according to the number of coils employed. Dynamo, Ring. A dynamo the base of whose field magnets is a ring in general shape, or perhaps an octagon, and with poles projecting inwardly therefrom. 201 STANDARD ELECTRICAL DICTIONARY. Dynamo, Coupling of. Dynamos can be coupled exactly like batteries and with about the same general results. An instance of series coupling would be given by the dynamos in the three wire system when no current is passing through the neutral wire, and when the lamps on each side of it are lighted in equal number. Dynamo, Self-exciting. A dynamo which excites its own field. The majority of dynamos are of this construction. Others, especially alternating current machines, are separately excited, the field magnets being supplied with current from a separate dynamo or current generator. Dynamo, Separate Circuit. A dynamo in which the field magnet coils are entirely disconnected from the main circuit, and in which current for the field is supplied by special coils carried for the purpose by the same armature, or by a special one, in either case a special commutator being provided to collect the current. Dynamo, Separately Excited. A dynamo whose field magnets are excited by a separate current generator, such as a dynamo or even a battery. Alternating current dynamos are often of this construction. Direct current dynamos are not generally so. The term is the opposite of self-exciting. Fig. 140. SERIES DYNAMO. Dynamo, Series. A dynamo whose armature, field winding, and external circuit are all in series. In such a dynamo short circuiting or lowering the resistance of the external circuit strengthens the field, increases the electro-motive force and current strength and may injure the winding by heating the wire, and melting the insulation. 202 STANDARD ELECTRICAL DICTIONARY. Dynamo, Shunt. A dynamo whose field is wound in shunt with the external circuit. Two leads are taken from the brushes; one goes around the field magnets to excite them; the other is the external circuit. In such a dynamo the lowering of resistance on the outer circuit takes current from the field and lowers the electro-motive force of the machine. Short circuiting has no heating effect. Fig. 141. SHUNT DYNAMO. Dynamo, Single Coil. A dynamo whose field magnet is excited by a single coil. Several such have been constructed, with different shapes of field magnet cores, in order to obtain a proper distribution of poles. Dynamo, Tuning Fork. A dynamo in which the inductive or armature coils were carried at the ends of the prongs of a gigantic tuning fork, and were there maintained in vibration opposite the field magnets. It was invented by T. A. Edison, but never was used. Dynamo, Uni-polar. A dynamo in which the rotation of a conductor effects a continuous increase in the number of lines cut, by the device of arranging one part of the conductor to slide on or around the magnet. (S. P. Thomson.) Faraday's disc is the earliest machine of this type. 203 STANDARD ELECTRICAL DICTIONARY. Dyne. The C. G. S. or fundamental unit of force. It is the force which can impart an acceleration of one centimeter per second to a mass of one gram in one second. It is equal to about 1/981 the weight of a gram, this weight varying with the latitude. Earth. (a) The earth is arbitrarily taken as of zero electrostatic potential. Surfaces in such condition that their potential is unchanged when connected to the earth are said to be of zero potential. All other surfaces are discharged when connected to the earth, whose potential, for the purposes of man at least, never changes. (b) As a magnetic field of force the intensity of the earth's field is about one-half a line of force per square centimeter. (c) The accidental grounding of a telegraph line is termed an earth, as a dead, total, partial, or intermittent earth, describing the extent and character of the trouble. [Transcriber's note: Fallen power lines can produce voltage gradients on the earth's surface that make walking in the area dangerous, as in hundreds of volts per foot. Lightning may be associated with substantial changes in the static ground potential.] Earth, Dead. A fault, when a telegraph or other conductor is fully connected to earth or grounded at some intermediate point. Synonyms--Solid Earth--Total Earth. Earth, Partial. A fault, when a telegraph or other conductor is imperfectly connected to earth or grounded at some intermediate point. Earth Plate. A plate buried in the earth to receive the ends of telegraph lines or other circuits to give a ground, q. v. A copper plate is often used. A connection to a water or gas main gives an excellent ground, far better than any plate. When the plate oxidizes it is apt to introduce resistance. Earth Return. The grounding of a wire of a circuit at both ends gives the circuit an earth return. Earth, Swinging. A fault, when a telegraph or other conductor makes intermittent connection with the earth. It is generally attributable to wind action swinging the wire, whence the name. Ebonite. Hard vulcanized India rubber, black in color. Specific resistance in ohms per cubic centimeter at 46º C. (115º F.): 34E15 (Ayrton); specific inductive capacity, (air = 1): 2.56 (Wüllner); 2.76 (Schiller); 3.15 (Boltzmann). It is used in electrical apparatus for supporting members such as pillars, and is an excellent material for frictional generation of potential. Its black color gives it its name, and is sometimes made a point of distinction from Vulcanite, q. v. 204 STANDARD ELECTRICAL DICTIONARY. Economic Coefficient. The coefficient of electric efficiency. (See Efficiency, Electric.) Edison Effect. A continuous discharge resulting in a true current which takes place between a terminal of an incandescent lamp filament and a plate placed near it. The lamp must be run at a definitely high voltage to obtain it. Ediswan. An abbreviation for Edison-Swan; the trade name of the incandescent lamp used in Great Britain, and of other incandescent system apparatus. Fig. 142. GYMNOTUS ELECTRICUS. Eel, Electric (Gymnotus Electricus). An eel capable of effecting the discharge of very high potential electricity, giving painful or dangerous shocks. Its habitat is the fresh water, in South America. Faraday investigated it and estimated its shock as equal to that from fifteen Leyden jars, each of 1.66 square feet of coating. (See Animal Electricity and Ray, Electric.) Effect, Counter-inductive. A counter-electro-motive force due to induction, and opposing a current. Efficiency. The relation of work done to energy absorbed. A theoretically perfect machine would have the maximum efficiency in which the two qualities named would be equal to each other. Expressed by a coefficient, q. v., the efficiency in such case would be equal to 1. If a machine produced but half the work represented by the energy it absorbed, the rest disappearing in wasteful expenditure, in heating the bearings, in overcoming the resistance of the air and in other ways, its efficiency would be expressed by the coefficient 1/2 or .5, or if one hundred was the basis, by fifty per centum. There are a number of kinds of efficiencies of an electric generator which are given below. Efficiency, Commercial. Practical efficiency of a machine, obtained by dividing the available output of work or energy of a machine by the energy absorbed by the same machine. Thus in a dynamo part of the energy is usefully expended in exciting the field magnet, but this energy is not available for use in the outer circuit, is not a part of the output, and is not part of the dividend. If M represents the energy absorbed, and W the useful or available energy, the coefficient of commercial efficiency is equal to W/M. M is made up of available, unavailable and wasted (by Foucault currents, etc.,) energy. Calling available energy W, unavailable but utilized energy w, and wasted energy m, the expression for the coefficient of commercial efficiency becomes W / ( W + w + m ) when M = W + w + m Synonym--Net efficiency. 205 STANDARD ELECTRICAL DICTIONARY. Efficiency, Electrical. In a dynamo or generator the relation of total electric energy produced, both wasted and useful or available to the useful or available electrical energy. If we call W the useful electric and w the wasted electric energy, the coefficient of electrical efficiency is equal to W / ( W + w ) Synonyms--Intrinsic Efficiency--Economic Coefficient--Coefficient of Electrical Efficiency. Efficiency of Conversion. In a dynamo or generator the relation of energy absorbed to total electric energy produced. Part of the electric energy is expended in producing the field and in other ways. Thus a generator with high efficiency of conversion may be a very poor one, owing to the unavailable electric energy which it produces. The coefficient of Efficiency of Conversion is obtained by dividing the total electric energy produced by the energy absorbed in working the dynamo. If M represents the energy absorbed, or work done in driving the dynamo or generator, W the useful electric, and w the wasted electrical energy, then the coefficient of efficiency of conversion is equal to (W + w ) / M In the quantity M are included besides available (W) and unavailable (w) electric energy, the totally wasted energy due to Foucault currents, etc., calling the latter m, the above formula may be given ( W+ w ) / (W + w + m ) This coefficient may refer to the action of a converter, q. v., in the alternating system. Synonym--Gross Efficiency. Efficiency of Secondary Battery, Quantity. The coefficient obtained by dividing the ampere-hours obtainable from a secondary battery by the ampere hours required to charge it. Efficiency of Secondary Battery, Real. The coefficient obtained by dividing the energy obtainable from a secondary battery by the energy absorbed in charging it. The energy is conveniently taken in watt-hours and includes the consideration of the spurious voltage. (See Battery, Secondary.) 206 STANDARD ELECTRICAL DICTIONARY. Efflorescence. The appearance of a dry salt upon the walls of a vessel containing a solution above the normal water-line from evaporation of a liquid. It appears in battery jars and in battery carbons, in the latter interfering with the electrical connections, and oxidizing or rusting them. (See Creeping.) Effluvium, Electric. When a gas is made to occupy the position of dielectric between two oppositely electrified surfaces a peculiar strain or condition of the dielectric is produced, which promotes chemical change. The condition is termed electrical effluvium or the silent discharge. By an apparatus specially constructed to utilize the condition large amounts of ozone are produced. Synonym--Silent Discharge. Elastic Curve. A crude expression for a curve without projections or sudden sinuosities; such a curve as can be obtained by bending an elastic strip of wood. Electrepeter. An obsolete name for a key, switch or pole changer of any kind. Elasticity, Electric. The phenomenon of the dielectric is described under this term. When a potential difference is established between two parts of the dielectric, a flow of electricity displacement current starts through the dielectric, which current is due to the electric stress, but is instantly arrested by what has been termed the electric elasticity of the dielectric. This is expressed by ( electric stress ) / ( electric strain ) and in any substance is inversely proportional to the specific inductive capacity. Electricity. It is impossible in the existing state of human knowledge to give a satisfactory definition of electricity. The views of various authorities are given here to afford a basis for arriving at the general consensus of electricians. We have as yet no conception of electricity apart from the electrified body; we have no experience of its independent existence. (J. E. H. Gordon.) What is Electricity? We do not know, and for practical purposes it is not necessary that we should know. (Sydney F. Walker.) Electricity … is one of those hidden and mysterious powers of nature which has thus become known to us through the medium of effects. (Weale's Dictionary of Terms.) This word Electricity is used to express more particularly the cause, which even today remains unknown, of the phenomena that we are about to explain. (Amédée Guillemin.) 207 STANDARD ELECTRICAL DICTIONARY. Electricity is a powerful physical agent which manifests itself mainly by attractions and repulsions, but also by luminous and heating effects, by violent commotions, by chemical decompositions, and many other phenomena. Unlike gravity, it is not inherent in bodies, but it is evoked in them by a variety of causes … (Ganot's Physics.) Electricity and magnetism are not forms of energy; neither are they forms of matter. They may, perhaps, be provisionally defined as properties or conditions of matter; but whether this matter be the ordinary matter, or whether it be, on the other hand, that all-pervading ether by which ordinary matter is surrounded, is a question which has been under discussion, and which now may be fairly held to be settled in favor of the latter view. (Daniell's Physics.) The name used in connection with an extensive and important class of phenomena, and usually denoting the unknown cause of the phenomena or the science that treats of them. (Imperial Dictionary.) Electricity. . . is the imponderable physical agent, cause, force or the molecular movement, by which, under certain conditions, certain phenomena, chiefly those of attraction and repulsion, . . . are produced. (John Angell.) It has been suggested that if anything can rightly be called "electricity," this must be the ether itself; and that all electrical and magnetic phenomena are simply due to changes, strains and motions in the ether. Perhaps negative electrification. . .means an excess of ether, and positive electrification a defect of ether, as compared with the normal density. (W. Larden.) Electricity is the name given to the supposed agent producing the described condition (i. e. electrification) of bodies. (Fleeming Jenkin.) There are certain bodies which, when warm and dry, acquire by friction, the property of attracting feathers, filaments of silk or indeed any light body towards them. This property is called Electricity, and bodies which possess it are said to be electrified. (Linnaeus Cumming.) What electricity is it is impossible to say, but for the present it is convenient to look upon it as a kind of invisible something which pervades all bodies. (W. Perren Maycock.) What is electricity? No one knows. It seems to be one manifestation of the energy which fills the universe and which appears in a variety of other forms, such as heat, light, magnetism, chemical affinity, mechanical motion, etc. (Park Benjamin.) 208 STANDARD ELECTRICAL DICTIONARY. The theory of electricity adopted throughout these lessons is, that electricity, whatever its true nature, is one, not two; that this Electricity, whatever it may prove to be, is not matter, and is not energy; that it resembles both matter and energy in one respect, however, in that it can neither be created nor destroyed. (Sylvanus P. Thomson.) In Physics a name denoting the cause of an important class of phenomena of attraction and repulsion, chemical decomposition, etc., or, collectively, these phenomena themselves. (Century Dictionary.) A power in nature, often styled the electric fluid, exhibiting itself, when in disturbed equilibrium or in activity, by a circuit movement, the fact of direction in which involves polarity, or opposition of properties in opposite directions; also, by attraction for many substances, by a law involving attraction between substances of unlike polarity, and repulsion between those of like; by exhibiting accumulated polar tension when the circuit is broken; and by producing heat, light, concussion, and often chemical changes when the circuit passes between the poles, or through any imperfectly conducting substance or space. It is evolved in any disturbance of molecular equilibrium, whether from a chemical, physical, or mechanical cause. (Webster's Dictionary.) In point of fact electricity is not a fluid at all, and only in a few of its attributes is it at all comparable to a fluid. Let us rather consider electricity to be a condition into which material substances are thrown. . .(Slingo & Brooker.) [Transcriber's note: 2008 Dictionary: Phenomena arising from the behavior of electrons and protons caused by the attraction of particles with opposite charges and the repulsion of particles with the same charge.] Electricity, Cal. The electricity produced in the secondary of a transformer by changes of temperature in the core. This is in addition to the regularly induced current. Synonym--Acheson Effect. Electrics. Substances developing electrification by rubbing or friction; as Gilbert, the originator of the term, applied it, it would indicate dielectrics. He did not know that, if insulated, any substance was one of his "electrics." A piece of copper held by a glass handle becomes electrified by friction. Electrification. The receiving or imparting an electric charge to a surface; a term usually applied to electrostatic phenomena. Electrization. A term in electro-therapeutics; the subjection of the human system to electric treatment for curative, tonic or diagnostic purposes. Electro-biology. The science of electricity in its relation to the living organism, whether as electricity is developed by the organism, or as it affects the same when applied from an external source. 209 STANDARD ELECTRICAL DICTIONARY. Electro-capillarity. The relations between surface tension, the potential difference and the electrostatic capacity of fluids in contact. Although nominally in contact such surfaces are separated by about one-twenty-millionth of a centimeter (1/50000000 inch) ; thus a globule of mercury and water in which it is immersed constitute an electrostatic accumulator of definite electrostatic capacity. Again the mercury and water being in electric connection differ in potential by contact (see Contact Theory). A definite surface tension is also established. Any change in one of these factors changes the other also. A current passed through the contact surfaces will change the surface tension and hence the shape of the mercury globule. Shaking the globule will change its shape and capacity and produce a current. Heating will do the same. (See Electrometer, Capillary; and Telephone, Capillary.) Mercury and water are named as liquids in which the phenomena are most conveniently observed. They are observable in other parallel cases. Electro-chemical Equivalent. The quantity of an element or compound liberated from or brought into combination, electrolytically, by one coulomb of electricity. The electro-chemical equivalent of hydrogen is found by experiment to be .0000105 gram. That of any other substance is found by multiplying this weight by its chemical equivalent referred to hydrogen, which is its atomic or molecular weight divided by its valency. Thus the atomic weight of oxygen is 16, its valency is 2, its equivalent is 16/2 = 8; its electro-chemical equivalent is equal to .0000105 X 8 = .000840 gram. Electro-chemical Series. An arrangement of the elements in the order of their relative electrical affinities so that each element is electro-negative to all the elements following it, and electro-positive to the elements preceding it. The usual series begins with oxygen as the most electro-negative and ends with potassium as the most electro-positive element. There is, of course, no reason why other series of compound radicals, such as sulphion (SO4), etc., should not also be constructed. For each liquid acting on substances a separate series of the substances acted on may be constructed. Thus for dilute sulphuric acid the series beginning with the negatively charged or most attacked one is zinc, amalgamated or pure, cadmium, iron, tin, lead, aluminum, nickel, antimony, bismuth, copper, silver, platinum. In other liquids the series is altogether different. Electro--chemistry. The branch of electricity or of chemistry treating of the relations between electric and chemical force in different compounds and reactions. (See Electrolysis--Electrochemical series--Electro-chemical Equivalent .) 210 STANDARD ELECTRICAL DICTIONARY. Electro-culture. The application of electricity to the cultivation of plants. In one system wires are stretched or carried across the bed under the surface, and some are connected to one pole and others to the other pole of a galvanic battery of two or more elements. In some experiments improved results have thus been obtained. Another branch refers to the action of the electric arc light on vegetation. This has an effect on vegetation varying in results. Electrode. (a) The terminal of an open electric circuit. (b) The terminals of the metallic or solid conductors of an electric circuit, immersed in an electrolytic solution. (c) The terminals between which a voltaic arc is formed, always in practice made of carbon, are termed electrodes. (d) In electro-therapeutics many different electrodes are used whose names are generally descriptive of their shape, character, or uses to which they are to be applied. Such are aural electrodes for the ears, and many others. (e) The plates of a voltaic battery. Electrode, Indifferent. A term in electro-therapeutics. An electrode to which no therapeutic action is attributed but which merely provides a second contact with the body to complete the circuit through the same. The other electrode is termed the therapeutic electrode. Electrodes, Erb's Standards of. Proposed standard sizes for medical electrodes as follows: Name. Diameter. Fine Electrode, 1/2 centimeter .2 inch Small " 2 " .8 " Medium " 7.5 " 3.0 " Large " 6X2 " 2.4 X .8 " Very large " 16x8 " 6.4 x 3.2 " Electrodes, Non-polarizable. In electro-therapeutics electrodes whose contact surface is virtually porous clay saturated with zinc chloride solution. The series terminate in amalgamated zinc ends, enclosed each in a glass tube, and closed with clay. Contact of metal with the tissues is thus avoided. Electrode, Therapeutic. A term in electro-therapeutics. An electrode applied to the body for the purpose of inducing therapeutic action, or for giving the basis for an electric diagnosis of the case. The other electrode is applied to complete the circuit only; it is termed the indifferent electrode. Electro-diagnosis. The study of the condition of a patient by the reactions which occur at the terminals or kathode and anode of an electric circuit applied to the person. The reactions are divided into kathodic and anodic reactions. 211 STANDARD ELECTRICAL DICTIONARY. Electro-dynamic. adj. The opposite of electrostatic; a qualification of phenomena due to current electricity. Synonym--Electro-kinetic. Electro-dynamic Attraction and Repulsion. The mutual attraction and repulsion exercised by currents of electricity upon each other. The theory of the cause is based upon stress of the luminiferous ether and upon the reaction of lines of force upon each other. For a resumé of the theory see Induction, Electro-magnetic. Electro-dynamics. The laws of electricity in a state of motion; the inter-reaction of electric currents. It is distinguished from electro-magnetic induction as the latter refers to the production of currents by induction. The general laws of electro-dynamics are stated under Induction, Electro-magnetic, q. v. Synonym--Electro-kinetics. Fig. 143. DIAGRAM OF CONNECTIONS OF SIEMENS' ELECTRO-DYNAMOMETER. 212 STANDARD ELECTRICAL DICTIONARY. Electro-dynamometer, Siemens'. An apparatus for measuring currents by the reaction between two coils, one fixed and one movable, through which the current to be measured passes. It is one of the oldest commercial ammeters or current measurers. It comprises a fixed coil of a number of convolutions and a movable coil often of only one convolution surrounding the other. The movable coil is suspended by a filament or thread from a spiral spring. The spring is the controlling factor. Connection is established through mercury cups so as to bring the two coils in series. In use the spring and filament are adjusted by turning a milled head to which they are connected until the coils are at right angles. Then the current is turned on and deflects the movable coil. The milled head is turned until the deflection is overcome. The angle through which the head is turned is proportional to the square of the current. The movable coil must in its position at right angles to the fixed one lie at right angles to the magnetic meridian. Thus in the diagram, Fig. 143 A B C D is the fixed coil; E F G H is the movable coil; S is the spiral spring attached at K to the movable coil. The arrows show the course of the current as it goes through the coils. Electrolier. A fixture for supporting electric lamps; the analogue in electric lighting of the gasolier or gas chandelier. Often both are combined, the same fixture being piped and carrying gas burners, as well as being wired and carrying electric lamps. Electrolysis. The separation of a chemical compound into its constituent parts or elements by the action of the electric current. The compound may be decomposed into its elements, as water into hydrogen and oxygen, or into constituent radicals, as sodium sulphate into sodium and sulphion, which by secondary reactions at once give sodium hydrate and sulphuric acid. The decomposition proceeds subject to the laws of electrolysis. (See Electrolysis, Laws of.) For decomposition to be produced there is for each compound a minimum electro-motive force or potential difference required. The current passes through the electrolyte or substance undergoing decomposition entirely by Electrolytic Conduction, q. v. in accordance with Grothüss' Hypothesis, q. v. The electrolyte therefore must be susceptible of diffusion and must be a fluid. The general theory holds that under the influence of a potential difference between electrodes immersed in an electrolyte, the molecules touching the electrodes are polarized, in the opposite sense for each electrode. If the potential difference is sufficient the molecules will give up one of their binary constituents to the electrode, and the other constituent will decompose the adjoining molecule, and that one being separated into the same two constituents will decompose its neighbor, and so on through the mass until the other electrode is reached. This one separates definitely the second binary constituent from the molecules touching it. 213 STANDARD ELECTRICAL DICTIONARY. Thus there is an exact balance preserved. Just as many molecules are decomposed at one electrode as at the other, and the exact chain of decomposition runs through the mass. Each compound electrolyzed develops a binary or two-fold composition, and gives up one constituent to one electrode and the other to the other. Fig. 144. ACTION OF MOLECULES IN A SOLUTION BEFORE AND DURING ELECTROLYSIS. The cut shows the assumed polarization of an electrolyte. The upper row shows the molecules in irregular order before any potential difference has been produced, in other words, before the circuit is closed. The next row shows the first effects of closing the circuit, and also indicates the polarization of the mass, when the potential difference is insufficient for decomposition. The third row indicates the decomposition of a chain of molecules, one constituent separating at each pole. 214 STANDARD ELECTRICAL DICTIONARY. Electrolysis, Laws of. The following are the principal laws, originally discovered by Faraday, and sometimes called Faraday's Laws of Electrolysis: 1. Electrolysis cannot take place unless the electrolyte is a conductor. Conductor here means an electrolytic conductor, one that conducts by its own molecules traveling, and being decomposed. (See Grothüss' Hypothesis.) II. The energy of the electrolytic action of the current is the same wherever exercised in different parts of the circuit. III. The same quantity of electricity--that is the same current for the same period----- decomposes chemically equivalent quantities of the bodies it decomposes, or the weights of elements separated in electrolytes by the same quantity of electricity (in coulombs or some equivalent unit) are to each other as their chemical equivalent. IV. The quantity of a body decomposed in a given time is proportional to the strength of the current. To these may be added the following: V. A definite and fixed electro-motive force is required for the decomposition of each compound, greater for some and less for others. Without sufficient electro-motive force expended on the molecule no decomposition will take place. (See Current, Convective.) Electrolyte. A body susceptible of decomposition by the electric current, and capable of electrolytic conduction. It must be a fluid body and therefore capable of diffusion, and composite in composition. An elemental body cannot be an electrolyte. Electrolytic Analysis. Chemical analysis by electrolysis. The quantitative separation of a number of metals can be very effectively executed. Thus, suppose that a solution of copper sulphate was to be analyzed. A measured portion of the solution would be introduced into a weighed platinum vessel. The vessel would be connected to the zinc plate terminal of a battery. From the other terminal of the battery a wire would be brought and would terminate in a plate of platinum. This would be immersed in the solution in the vessel. As the current would pass the copper sulphate would be decomposed and eventually all the copper would be deposited in a firm coating on the platinum. The next operations would be to wash the metal with distilled water, and eventually with alcohol, to dry and to weigh the dish with the adherent copper. On subtracting the weight of the dish alone from the weight of the dish and copper, the weight of the metallic copper in the solution would be obtained. In similar ways many other determinations are effected. The processes of analysis include solution of the ores or other substances to be analyzed and their conversion into proper form for electrolysis. Copper as just described can be precipitated from the solution of its sulphate. For iron and many other metals solutions of their double alkaline oxalates are especially available forms for analysis. The entire subject has been worked out in considerable detail by Classen, to whose works reference should be made for details of processes. Electrolytic Convection. It is sometimes observed that a single cell of Daniell battery, for instance, or other source of electric current establishing too low a potential difference for the decomposition of water seems to produce a feeble but continuous decomposition. This is very unsatisfactorily accounted for by the hydrogen as liberated combining with dissolved oxygen. (Ganot.) The whole matter is obscure. (See Current, Convection.) 215 STANDARD ELECTRICAL DICTIONARY. Electrolytic Conduction. Conduction by the travel of atoms or radicals from molecule to molecule of a substance with eventual setting free at the electrodes of the atoms or radicals as elementary molecules or constituent radicals. A substance to be capable of acting as an electrolytic conductor must be capable of diffusion, and must also have electrolytic conductivity. Such a body is called an electrolyte. (See Grothüss' Hypothesis--Electrolysis-- Electrolysis, Laws of--Electro-chemical Equivalent.) Electro-magnet. A mass, in practice always of iron, around which an electric circuit is carried, insulated from the iron. When a current is passed through the circuit the iron presents the characteristics of a magnet. (See Magnetism, Ampére's Theory of--Solenoid--Lines of Force.) In general terms the action of a circular current is to establish lines of force that run through the axis of the circuit approximately parallel thereto, and curving out of and over the circuit, return into themselves outside of the circuit. If a mass of iron is inserted in the axis or elsewhere near such current, it multiplies within itself the lines of force, q. v. (See also Magnetic Permeability--Permeance--Magnetic Induction, Coefficient of Magnetic Susceptibility--Magnetization, Coefficient of Induced.) These lines of force make it a magnet. On their direction, which again depends on the direction of the magnetizing current, depends the polarity of the iron. The strength of an electro-magnet, below saturation of the core (see Magnetic Saturation), is proportional nearly to the ampere-turns, q. v. More turns for the same current or more current for the same turns increase its strength. In the cut is shown the general relation of current, coils, core and line of force. Assume that the magnet is looked at endwise, the observer facing one of the poles; then if the current goes around the core in the direction opposite to that of the hands of a clock, such pole will be the north pole. If the current is in the direction of the hands of a clock the pole facing the observer will be the south pole. The whole relation is exactly that of the theoretical Ampérian currents, already explained. The direction and course of the lines of force created are shown in the cut. The shapes of electro-magnets vary greatly. The cuts show several forms of electro-magnets. A more usual form is the horseshoe or double limb magnet, consisting generally of two straight cores, wound with wire and connected and held parallel to each other by a bar across one end, which bar is called the yoke. In winding such a magnet the wire coils must conform, as regards direction of the current in them to the rule for polarity already cited. If both poles are north or both are south poles, then the magnet cannot be termed a horseshoe magnet, but is merely an anomalous magnet. In the field magnets of dynamos the most varied types of electro-magnets have been used. Consequent poles are often produced in them by the direction of the windings and connections. To obtain the most powerful magnet the iron core should be as short and thick as possible in order to diminish the reluctance of the magnetic circuit. To obtain a greater range of action a long thin shape is better, although it involves waste of energy in its excitation. 216 STANDARD ELECTRICAL DICTIONARY. Fig. 145 DIAGRAM OF AN ELECTRO-MAGNET SHOWING RELATION OF CURRENT AND WINDING TO ITS POLARITY AND LINES OF FORCE. Fig. 146. ANNULAR ELECTRO-MAGNET Electro-magnet, Annular. An electro-magnet consisting of a cylinder with a circular groove cut in its face, in which groove a coil of insulated wire is placed. On the passage of a current the iron becomes polarized and attracts an armature towards or against its grooved face. The cut shows the construction of an experimental one. It is in practice applied to brakes and clutches. In the cut of the electro-magnetic brake (see Brake, Electro-magnetic), C is the annular magnet receiving its current through the brushes, and pressed when braking action is required against the face of the moving wheel. The same arrangement, it can be seen, may apply to a clutch. 217 STANDARD ELECTRICAL DICTIONARY. Fig. 147. BAR ELECTRO-MAGNET. Electro-magnet, Bar. A straight bar of iron surrounded with a magnetizing coil of wire. Bar electromagnets are not much used, the horseshoe type being by far the more usual. Electro-magnet, Club-foot. An electro-magnet, one of whose legs only is wound with wire, the other being bare. Fig. 148. CLUB-FOOT ELECTRO-MAGNETS WITH HINGED ARMATURES. Electro-magnet, Hinged. An electro-magnet whose limbs are hinged at the yoke. On excitation by a current the poles tend to approach each other. Fig. 149. ELECTRO-MAGNET, HINGED Electro-magnetic Attraction and Repulsion. The attraction and repulsion due to electromagnetic lines of force, which lines always tend to take as short a course as possible and also seek the medium of the highest permeance. This causes them to concentrate in iron and steel or other paramagnetic substance and to draw them towards a magnet by shortening the lines of force connecting the two. It is exactly the same attraction as that of the permanent magnet for its armature, Ampére's theory bringing the latter under the same title. In the case of two magnets like poles repel and unlike attract. In the case of simple currents, those in the same direction attract and those in opposite directions repel each other. This refers to constant current reactions. Thus the attraction of unlike poles of two magnets is, by the Ampérian theory, the attraction of two sets of currents of similar direction, as is evident from the diagram. The repulsion of like poles is the repulsion of unlike currents and the same applies to solenoids, q. v. (See Magnetism and do. Ampére's Theory of--Induction, Electro-dynamic--Electro-magnetic Induction.) 218 STANDARD ELECTRICAL DICTIONARY. Electro-magnetic Control. Control of a magnet, iron armature, or magnetic needle in a galvanometer, ammeter, voltmeter or similar instrument by an electro-magnetic field, the restitutive force being derived from an electro-magnet. The restitutive force is the force tending to bring the index to zero. Electro-magnetic Field of Force. A field of electro-magnetic lines of force, q. v., established through the agency of an electric current. A wire carrying a current is surrounded by circular concentric lines of force which have the axis of the wire as the locus of their centres. Electro-magnets produce lines of force identical with those produced by permanent magnets. (See Field of Force--Magnetic Field of Force--Controlling Field--Deflecting Field.) Electro-magnetic Induction. When two currents of unlike direction are brought towards each other, against their natural repulsive tendency work is done, and the consequent energy takes the form of a temporary increase in both currents. When withdrawn, in compliance with the natural tendency of repulsion, the currents are diminished in intensity, because energy is not expended on the withdrawal, but the withdrawal is at the expense of the energy of the system. The variations thus temporarily produced in the currents are examples of electro-magnetic induction. The currents have only the duration in each case of the motion of the circuits. One circuit is considered as carrying the inducer current and is termed the primary circuit and its current the primary current, the others are termed the secondary circuit and current respectively. We may assume a secondary circuit in which there is no current. It is probable that there is always an infinitely small current at least, in every closed circuit. Then an approach of the circuits will induce in the secondary an instantaneous current in the reverse direction. On separating the two circuits a temporary current in the same direction is produced in the secondary. 219 STANDARD ELECTRICAL DICTIONARY. A current is surrounded by lines of force. The approach of two circuits, one active, involves a change in the lines of force about the secondary circuit. Lines of force and current are so intimately connected that a change in one compels a change in the other. Therefore the induced current in the secondary may be attributed to the change in the field of force in which it lies, a field maintained by the primary circuit and current. Any change in a field of force induces a current or change of current in any closed circuit in such field, lasting as long as the change is taking place. The new current will be of such direction as to oppose the change. (See Lenz's Law.) The action as referred to lines of force may be figured as the cutting of such lines by the secondary circuit, and such cutting may be brought about by moving the secondary in the field. (See Lines of Force--Field of Force.) The cutting of 1E8 lines of force per second by a closed circuit induces an electro-motive force of one volt. (See Induction, Mutual, Coefficient of.) Electro-magnet, Iron Clad. A magnet whose coil and core are encased in a iron jacket, generally connected to one end of the core. This gives at one end two poles, one tubular, the other solid, and concentric with each other. It is sometimes called a tubular magnet. Electro-magnet, One Coil. An electro-magnet excited by one coil. In some dynamos the field magnets are of this construction, a single coil, situated about midway between the poles, producing the excitation. Electro-magnetic Leakage. The leakage of lines of force in an electro-magnet; the same as magnetic leakage. (See Magnetic Leakage.) Electro-magnetic Lines of Force. The lines of force produced in an electro-magnetic field. They are identical with Magnetic Lines of Force, q. v. (See also Field of Force-Line of Force.) Electro-magnetic Stress. The stress in an electro-magnetic field of force, showing itself in the polarization of light passing through a transparent medium in such a field. (See Magnetic Rotary Polarization.) Electro-magnetic Theory of Light. This theory is due to J. Clark Maxwell, and the recent Hertz experiments have gone far to prove it. It holds that the phenomena of light are due to ether waves, identical in general factors with those produced by electro-magnetic induction of alternating currents acting on the ether. In a non-conductor any disturbance sets an ether wave in motion owing to its restitutive force; electricity does not travel through such a medium, but can create ether waves in it. Therefore a non-conductor of electricity is permeable to waves of ether or should transmit light, or should be transparent. A conductor on the other hand transmits electrical disturbances because it has no restitutive force and cannot support an ether wave. Hence a conductor should not transmit light, or should be opaque. With few exceptions dielectrics or non-conductors are transparent, and conductors are opaque. 220 STANDARD ELECTRICAL DICTIONARY. Again, the relation between the electrostatic and electro-magnet units of quantity is expressed by 1 : 30,000,000,000; the latter figure in centimeters gives approximately the velocity of light. The electro-magnetic unit depending on electricity in motion should have this precise relation if an electro-magnetic disturbance was propagated with the velocity of light. If an electrically charged body were whirled around a magnetic needle with the velocity of light, it should act in the same way as a current circulating around it. This effect to some extent has been shown experimentally by Rowland. A consequence of these conclusions is (Maxwell) that the specific inductive capacity of a non-conductor or dielectric should be equal to the square of its index of refraction for waves of infinite length. This is true for some substances--sulphur, turpentine, petroleum and benzole. In others the specific inductive capacity is too high, e. g., vegetable and animal oils, glass, Iceland spar, fluor spar, and quartz. Electro-magnetic Unit of Energy. A rate of transference of energy equal to ten meg-ergs per second. Electro-magnetism. The branch of electrical science treating of the magnetic relations of a field of force produced by a current, of the reactions of electro-magnetic lines of force, of the electromagnetic field of force, of the susceptibility, permeability, and reluctance of diamagnetic and paramagnetic substances, and of electro-magnets in general. Electro-magnet, Long Range. An electro-magnet so constructed with extended pole pieces or otherwise, as to attract its armature with reasonably constant force over a considerable distance. The coil and plunger, q. v., mechanisms illustrate one method of getting an extended range of action. When a true electro-magnet is used, one with an iron core, only a very limited range is attainable at the best. (See Electro-magnet, Stopped Coil--do. Plunger.) Electro-magnet, Plunger. An electro-magnet with hollow coils, into which the armature enters as a plunger. To make it a true electro-magnet it must have either a yoke, incomplete core, or some polarized mass of iron. Electro-magnet, Polarized. An electro-magnet consisting of a polarized or permanently magnetized core wound with magnetizing coils, or with such coils on soft iron cores mounted on its ends. The coils may be wound and connected so as to cooperate with or work against the permanent magnet on which it is mounted. In Hughes' magnet shown in the cut it is mounted in opposition, so that an exceedingly feeble current will act to displace the armature, a, which is pulled away from the magnet by a spring, s. 221 STANDARD ELECTRICAL DICTIONARY. Fig. 150 HUGHES' POLARIZED ELECTRO-MAGNET Electro-magnets, Interlocking. Electro-magnets so arranged that their armatures interlock. Thus two magnets, A A and B B, may be placed with their armatures, M and N, at right angles and both normally pulled away from the poles. When the armature M is attracted a catch on its end is retained by a hole in the end of the other armature N, and when the latter armature N is attracted by its magnet the armature M is released. In the mechanism shown in the cut the movements of the wheel R are controlled. Normally it is held motionless by the catch upon the bottom of the armature M, coming against the tooth projecting from its periphery. A momentary current through the coils of the magnet A A releases it, by attracting M, which is caught and retained by N, and leaves it free to rotate. A momentary current through the coils of the magnet B B again releases M, which drops down and engages the tooth upon R and arrests its motion. Fig. 151. INTERLOCKING ELECTRO-MAGNETS. 222 STANDARD ELECTRICAL DICTIONARY. Electro-magnet, Stopped Coil. An electro-magnet consisting of a tubular coil, in which a short fixed core is contained, stopping up the aperture to a certain distance, while the armature is a plunger entering the aperture. This gives a longer range of action than usual. Electro-magnet, Surgical. An electro-magnet, generally of straight or bar form, fitted with different shaped pole pieces, used for the extraction of fragments of iron or steel from the eyes. Some very curious cases of successful operations on the eyes of workmen, into whose eyes fragments of steel or iron had penetrated, are on record. Electro-medical Baths. A bath for the person provided with connections and electrodes for causing a current of electricity of any desired type to pass through the body of the bather. Like all electro-therapeutical treatment, it should be administered under the direction of a physician only. Electro-metallurgy. (a) In the reduction of ores the electric current has been proposed but never extensively used, except in the reduction of aluminum and its alloys. (See Reduction of Ores, Electric.) (b) Electro-plating and deposition of metal from solutions is another branch. (See Electroplating and Electrotyping.) (c) The concentration of iron ores by magnetic attraction may come under this head. (See Magnetic Concentration of Ores.) Electrometer. An instrument for use in the measurement of potential difference, by the attraction or repulsion of statically charged bodies. They are distinguished from galvanometers as the latter are really current measurers, even if wound for use as voltmeters, depending for their action upon the action of the current circulating in their coils. Electrometer, Absolute. An electrometer designed to give directly the value of a charge in absolute units. In one form a plate, a b, of conducting surface is supported or poised horizontally below a second larger plate C, also of conducting surface. The poised plate is surrounded by a detached guard ring--an annular or perforated plate, r g r' g'--exactly level and even with it as regards the upper surface. The inner plate is carried by a delicate balance. In use it is connected to one of the conductors and the lower plate to earth or to the other. The attraction between them is determined by weighing. By calculation the results can be made absolute, as they depend on actual size of the plates and their distance, outside of the potential difference of which of course nothing can be said. If S is the area of the disc, d the distance of the plates, V-V1 the difference of their potential, which is to be measured, and F the force required to balance their attraction, we have: F = ( ( V - V1 )^2 * S ) / ( 8 * PI * d^2 ) 223 STANDARD ELECTRICAL DICTIONARY. If V = 0 this reduces to F = ( V^2 * S ) / ( 8 * PI * d^2 ) (2) or V = d * SquareRoot( (8 * PI * F ) / S ) (3) As F is expressed as a weight, and S and a as measures of area and length, this gives a means of directly obtaining potential values in absolute measure. (See Idiostatic Method--Heterostatic Method.) Synonyms--Attracted Disc Electrometer--Weight Electrometer. Fig. 152. SECTION OF BASE OF PORTABLE ELECTROMETER. In some forms the movable disc is above the other, and supported at the end of a balance beam. In others a spring support, arranged so as to enable the attraction to be determined in weight units, is adopted. The cuts, Figs. 152 and 154, show one of the latter type, the portable electrometer. The disc portion is contained within a cylindrical vessel. Fig. 153. DIAGRAM ILLUSTRATING THEORY OF ABSOLUTE ELECTROMETER. Referring to Fig. 152 g is the stationary disc, charged through the wire connection r; f is the movable disc, carried by a balance beam poised at i on a horizontal and transverse stretched platinum wire, acting as a torsional spring. The position of the end k of the balance beam shows when the disc f is in the plane of the guard ring h h. The end k is forked horizontally and a horizontal sighting wire or hair is fastened across the opening of the fork. When the hair is midway between two dots on a vertical scale the lever is in the sighted position, as it is called, and the disc is in the plane of the guard ring. 224 STANDARD ELECTRICAL DICTIONARY. Fig. 154. PORTABLE ELECTROMETER. The general construction is seen in Fig. 154. There the fixed disc D is carried by insulating stem g1. The charging electrode is supported by an insulating stem g2, and without contact with the box passes out of its cover through a guard tube E, with cover, sometimes called umbrella, V. The umbrella is to protect the apparatus from air currents. At m is the sighting lens. H is a lead box packed with pumice stone, moistened with oil of vitriol or concentrated sulphuric acid, to preserve the atmosphere dry. Before use the acid is boiled with some ammonium sulphate to expel any corrosive nitrogen oxides, which might corrode the brass. In use the upper disc is charged by its insulated electrode within the tube E; the movable disc is charged if desired directly through the case of the instrument. The upper disc is screwed up or down by the micrometer head M, until the sighted position is reached. The readings of the micrometer on the top of the case give the data for calculation. 225 STANDARD ELECTRICAL DICTIONARY. Fig. 155. LIPPMAN'S CAPILLARY ELECTROMETER. Electrometer, Capillary. An electrometer for measuring potential difference by capillary action, which latter is affected by electrostatic excitement. A tube A contains mercury; its end drawn out to a fine aperture dips into a vessel B which contains dilute sulphuric acid with mercury under it, as shown. Wires running from the binding-posts a and b connect one with the mercury in A, the other with that in B. The upper end of the tube A connects with a thick rubber mercury reservoir T, and manometer H. The surface tension of the mercury-acid film at the lower end of the tube A keeps all in equilibrium. If now a potential difference is established between a and b, as by connecting a battery thereto, the surface tension is increased and the mercury rises in the tube B. By screwing down the compressing clamp E, the mercury is brought back to its original position. The microscope M is used to determine this position with accuracy. The change in reading of the manometer gives the relation of change of surface tension and therefore of potential. Each electrometer needs special graduation or calibration, but is exceedingly sensitive and accurate. It cannot be used for greater potential differences than .6 volt, but can measure .0006 volt. Its electrostatic capacity is so small that it can indicate rapid changes. Another form indicates potential difference by the movement of a drop of sulphuric acid in a horizontal glass tube, otherwise filled with mercury, and whose ends lead into two mercury cups or reservoirs. The pair of electrodes to be tested are connected to the mercury vessels. The drop moves towards the negative pole, and its movement for small potential differences (less than one volt) is proportional to the electro-motive force or potential difference. 226 STANDARD ELECTRICAL DICTIONARY. Electrometer Gauge. An absolute electrometer (see Electrometer, Absolute) forming an attachment to a Thomson quadrant electrometer. It is used to test the potential of the flat needle connected with the inner surface of the Leyden jar condenser of the apparatus. This it does by measuring the attraction between itself and an attracting disc, the latter connected by a conductor with the interior of the jar. Electrometer, Lane's. A Leyden jar with mounted discharger, so that when charged to a certain point it discharges itself. It is connected with one coating of any jar whose charge is to be measured, which jar is then charged by the other coating. As the jar under trial becomes charged to a certain point the electrometer jar discharges itself, and the number of discharges is the measure of the charge of the other jar. It is really a unit jar, q. v. Fig. 156. THOMSON'S QUADRANT ELECTROMETER. Fig. 157. HENLEY'S QUADRANT ELECTROSCOPE. 227 STANDARD ELECTRICAL DICTIONARY. Electrometer, Quadrant. (a) Sir William Thomson's electrometer, a simple form of which is shown in the cut, consists of four quadrants of metal placed horizontally; above these a broad flat aluminum needle hangs by a very fine wire, acting as torsional suspension. The quadrants are insulated from each other, but the opposite ones connect with each other by wires. The apparatus is adjusted so that, when the quadrants are in an unexcited condition the needle is at rest over one of the diametrical divisions between quadrants. The needle by its suspension wire is in communication with the interior of a Leyden jar which is charged. The whole is covered with a glass shade, and the air within is kept dry by a dish of concentrated sulphuric acid so that the jar retains its charge for a long time and keeps the needle at approximately a constant potential. If now two pairs of quadrants are excited with opposite electricities, as when connected with the opposite poles of an insulated galvanic cell, the needle is repelled by one pair and attracted by the other, and therefore rotates through an arc of greater or less extent. A small concave mirror is attached above the needle and its image is reflected on a graduated screen. This makes the smallest movement visible. Sometimes the quadrants are double, forming almost a complete box, within which the needle moves. (b) Henley's quadrant electrometer is for use on the prime conductor of an electric machine, for roughly indicating the relative potential thereof. It consists of a wooden standard attached perpendicularly to the conductor. Near one end is attached a semi-circular or quadrant arc of a circle graduated into degrees or angular divisions. An index, consisting of a straw with a pith-bell attached to its end hangs from the center of curvature of the arc. When the prime conductor is charged the index moves up over the scale and its extent of motion indicates the potential relatively. When the "quadrant electrometer" is spoken of it may always be assumed that Sir William Thomson's instrument is alluded to. Henley's instrument is properly termed a quadrant electroscope. (See Electroscope.) Electro-motive Force. The cause which produces currents of electricity. In general it can be expressed in difference of potentials, although the term electro-motive force should be restricted to potential difference causing a current. It is often a sustained charging of the generator terminals whence the current is taken. Its dimensions are (work done/the quantity of electricity involved), or ( M * (L^2) /(T^2 ) ) / ((M^.5) * (L^.5)) = ( (M^.5) * (L^1.5) ) /(T^2) The practical unit of electro-motive force is the volt, q. v. It is often expressed in abbreviated form, as E. M. D. P., or simply as D. P., i. e., potential difference. Electro-motive force and potential difference are in many cases virtually identical, and distinctions drawn between them vary with different authors. If we consider a closed electric circuit carrying a current, a definite electro-motive force determined by Ohm's law from the resistance and current obtains in it. But if we attempt to define potential difference as proper to the circuit we may quite fail. Potential difference in a circuit is the difference in potential between defined points of such circuit. But no points in a closed circuit can be found which differ in potential by an amount equal to the entire electro-motive force of the circuit. Potential difference is properly the measure of electro-motive force expended on the portion of a circuit between any given points. Electro-motive force of an entire circuit, as it is measured, as it were, between two consecutive points but around the long portion of the circuit, is not conceivable as merely potential difference. Taking the circle divided in to degrees as an analogy, the electro-motive force of the entire circuit might be expressed as 360º, which are the degrees intervening between two consecutive points, measured the long way around the circle. But the potential difference between the same two points would be only 1º, for it would be measured by the nearest path. [Transcriber's notes: If 360º is the "long" way, 0º is the "short". A formal restatement of the above definition of EMF: "If a charge Q passes through a device and gains energy U, the net EMF for that device is the energy gained per unit charge, or U/Q. The unit of EMF is a volt, or newton-meter per coulomb."] 228 STANDARD ELECTRICAL DICTIONARY. Electro-motive Force, Counter. A current going through a circuit often has not only true or ohmic resistance to overcome, but meets an opposing E. M. F. This is termed counter-electro-motive force. It is often treated in calculations as resistance, and is termed spurious resistance. It may be a part of the impedance of a circuit. In a primary battery hydrogen accumulating on the negative plate develops counter E. M. F. In the voltaic arc the differential heating of the two carbons does the same. The storage battery is changed by a current passing in the opposite direction to its own natural current; the polarity of such a battery is counter E. M. F. Electro-motive Force, Unit. Unit electro-motive force is that which is created in a conductor moving through a magnetic field at such a rate as to cut one unit line of force per second. It is that which must be maintained in a circuit of unit resistance to maintain a current of unit quantity therein. It is that which must be maintained between the ends of a conductor in order that unit current may do unit work in a second. Electro-motive Intensity. The force acting upon a unit charge of electricity. The mean force is equal to the difference of potential between two points within the field situated one centimeter apart, such distance being measured along the lines of force. The term is due to J. Clerk Maxwell. Electro-motive Series. Arrangement of the metals and carbon in series with the most electro-positive at one end, and electronegative at the other end. The following are examples for different exciting liquids: Dilute Sulphuric Dilute Hydrochloric Caustic Potassium Acid Acid. Potash. Sulphide. Zinc Zinc Zinc Zinc Cadmium Cadmium Tin Copper Tin Tin Cadmium Cadmium Lead Lead Antimony Tin Iron Iron Lead Silver Nickel Copper Bismuth Antimony Bismuth Bismuth Iron Lead Antimony Nickel Copper Bismuth Copper Silver Nickel Nickel Silver Antimony Silver Iron Gold Platinum Carbon In each series the upper metal is the positive, dissolved or attacked element. 229 STANDARD ELECTRICAL DICTIONARY. Electro-motograph. An invention of Thomas A. Edison. A cylinder of chalk, moistened with solution of caustic soda, is mounted so as to be rotated by a handle. A diaphragm has an arm connected to its center. This arm is pressed against the surface of the cylinder by a spring. When the cylinder is rotated, a constant tension is exerted on the diaphragm. If a current is passed through the junction of arm and cylinder the electrolytic action alters the friction so as to change the stress upon the diaphragm. If the current producing this effect is of the type produced by the human voice through a microphone the successive variations in strain upon the diaphragm will cause it to emit articulate sounds. These are produced directly by the movement of the cylinder, the electrolytic action being rather the regulating portion of the operation. Hence very loud sounds can be produced by it. This has given it the name of the loud- speaking telephone. The same principle may be applied in other ways. But the practical application of the motograph is in the telephone described. Fig. 158. ELECTRO-MOTOGRAPH TELEPHONE Electro-motor. This term is sometimes applied to a current generator, such as a voltaic battery. Electro-muscular Excitation. A term in medical electricity indicating the excitation of muscle as the effect of electric currents of any kind. Electro-negative. adj. Appertaining to negative electrification; thus of the elements oxygen is the most electro-negative, because if separated by electrolytic action from any combination, it will be charged with negative electricity. 230 STANDARD ELECTRICAL DICTIONARY. Electro-optics. The branch of natural science treating of the relations between light and electricity. Both are supposed to be phenomena of or due to the luminiferous ether. To it may be referred the following: (a) Electro-magnetic Stress and Magnetic Rotary Polarization; (b) Dielectric Strain; all of which may be referred to in this book; (c) Change in the resistance of a conductor by changes in light to which it is exposed (see Selenium); (d) The relation of the index of refraction of a dielectric to the dielectric constant (see Electro-magnetic Theory of Light); (e) The identity (approximate) of the velocity of light in centimeters and the relative values of the electrostatic and electro-magnet units of intensity, the latter being 30,000,000,000 times greater than the former, while the velocity of light is 30,000,000,000 centimeters per second. Electrophoric Action. The action of an electrophorous; utilized in influence machines. (See Electrophorous.) Fig. 159. ELECTROPHOROUS. Electrophorous. An apparatus for the production of electric charges of high potential by electrostatic induction, q. v. It consists of a disc of insulating material B, such as resin or gutta percha, which is held in a shallow metal-lined box or form. The disc may be half an inch thick and a foot or more in diameter, or may be much smaller and thinner. A metal disc A, smaller in diameter is provided with an insulating handle which may be of glass, or simply silk suspension strings. To use it the disc B is excited by friction with a cat-skin or other suitable substance. The metallic disc is then placed on the cake of resin exactly in its centre, so that the latter disc or cake projects on all sides. Owing to roughness there is little real electric contact between the metal and dielectric. On touching the metal disc a quantity of negative electricity escapes to the earth. On raising it from the cake it comes off excited positively, and gives a spark and is discharged. It can be replaced, touched, removed and another spark can be taken from it, and so on as long as the cake stays charged. The successive discharges represent electrical energy expended. This is derived from the muscular energy expended by the operator in separating the two discs when oppositely excited. As generally used it is therefore an apparatus for converting muscular or mechanical energy into electric energy. 231 STANDARD ELECTRICAL DICTIONARY. Electro-physiology. The science of the electric phenomena of the animal system. It may also be extended to include plants. The great discovery of Galvani with the frog's body fell into this branch of science. The electric fishes, gymnotus, etc., present intense phenomena in the same. Electroplating. The deposition by electrolysis of a coating of metal upon a conducting surface. The simplest system makes the object to be plated the negative electrode or plate in a galvanic couple. Thus a spoon or other object may be connected by a wire to a plate of zinc. A porous cup is placed inside a battery jar. The spoon is placed in the porous cup and the zinc outside it. A solution of copper sulphate is placed in the porous cup, and water with a little sodium or zinc sulphate dissolved in it, outside. A current starts through the couple, and copper is deposited on the spoon. A less primitive way is to use a separate battery as the source of current; to connect to the positive plate by a wire the object to be plated, and a plate of copper, silver, nickel or other metal to the other pole of the battery. On immersing both object and plate (anode) in a bath of proper solution the object will become plated. In general the anode is of the same material as the metal to be deposited, and dissolving keeps up the strength of the bath. There are a great many points of technicality involved which cannot be given here. The surface of the immersed object must be conductive. If not a fine wire network stretched over it will gradually fill up in the bath and give a matrix. More generally the surface is made conductive by being brushed over with plumbago. This may be followed by a dusting of iron dust, followed by immersion in solution ot copper sulphate. This has the effect of depositing metallic copper over the surface as a starter for the final coat. Attention must be paid to the perfect cleanliness of the objects, to the condition of the bath, purity of anodes and current density. Voltaic batteries are largely used for the current as well as special low resistance dynamos. Thermo-electric batteries are also used to some extent but not generally. Electro-pneumatic Signals. Signals, such as railroad signals or semaphores, moved by compressed air, which is controlled by valves operated by electricity. The House telegraph, which was worked by air controlled by electricity, might come under this term, but it is always understood as applied to railroad signals, or their equivalent. 232 STANDARD ELECTRICAL DICTIONARY. Electropoion Fluid. An acid depolarizing solution for use in zinc-carbon couples, such as the Grenet battery. The following are formulae for its preparation: (a) Dissolve one pound of potassium bichromate in ten pounds of water, to which two and one-half pounds of concentrated sulphuric acid have been gradually added. The better way is to use powdered potassium bichromate, add it to the water first, and then gradually add the sulphuric acid with constant stirring. (b) To three pints of water add five fluid ounces of concentrated sulphuric acid; add six ounces pulverized potassium bichromate. (c) Mix one gallon concentrated sulphuric acid and three gallons of water. In a separate vessel dissolve six pounds potassium bichromate in two gallons of boiling water. Mix the two. The last is the best formula. Always use electropoion fluid cold. (See Trouvé's Solution--Poggendorff's Solution--Kakogey's Solution-- Tissandrier's Solution--Chutaux's Solution.) Electro-positive. adj. Appertaining to positive electrification; thus potassium is the most electro-positive of the elements. (See Electro-negative.) Electro-puncture. The introduction into the system of a platinum point or needle, insulated with vulcanite, except near its point, and connected as the anode of a galvanic battery. The kathode is a metal one, covered with a wet sponge and applied on the surface near the place of puncture. It is used for treatment of aneurisms or diseased growths, and also for removal of hair by electrolysis. (See Hair, Removal of by Electrolysis.) Synonym--Galvano-puncture. Electro-receptive. adj. A term applied to any device or apparatus designed to receive and absorb electric energy. A motor is an example of an electro-receptive mechanism. Electroscope. An apparatus for indicating the presence of an electric charge, and also for determining the sign, or whether the charge is positive or negative. The simplest form consists of a thread doubled at its centre and hung therefrom. On being charged, or on being connected to a charged body the threads diverge. A pair of pith balls may be suspended in a similar way, or a couple of strips of gold leaf within a flask (the gold leaf electroscope). To use an electroscope to determine the sign of the charge it is first slightly charged. The body to be tested is then applied to the point of suspension, or other charging point. If at once further repelled the charge of the body is of the same sign as the slight charge first imparted to the electroscope leaves; the leaves as they become more excited will at once diverge more. If of different sign they will at first approach as their charge is neutralized and will afterwards diverge. The gold-leaf electroscope is generally enclosed in a glass bell jar or flask. Sometimes a pair of posts rise, one on each side, to supply points of induction from the earth to intensify the action. (See Electrometer, Quadrant--Electroscope, Gold leaf, and others.) 233 STANDARD ELECTRICAL DICTIONARY. Electroscope, Bennett's. A gold-leaf electroscope, the suspended leaves of which are contained in a glass shade or vessel of dry air. On the inside of the glass shade are two strips of gold leaf, which rise from the lower edge a short distance, being pasted to the glass, and connected to the ground. These act by induction to increase the sensitiveness of the instruments. Electroscope, Bohenberger's. A condensing electroscope (see Electroscope, Condensing) with a single strip of gold leaf suspended within the glass bell. This is at an equal distance from the opposite poles of two dry piles (see Zamboni's Dry Pile) standing on end, one on each side of it. As soon as the leaf is excited it moves toward one and away from the other pile, and the sign of its electrification is shown by the direction of its motion. Electroscope, Condensing. A gold leaf electroscope, the glass bell of which is surmounted by an electrophorous or static condenser, to the lower plate of which the leaves of gold are suspended or connected. In use the object to be tested is touched to the lower plate, and the upper plate at the same time is touched by the finger. The plates are now separated. This reduces the capacity of the lower plate greatly and its charge acquires sufficient potential to affect the leaves, although the simple touching may not have affected them at all. Electroscope, Gold Leaf. An electroscope consisting of two leaves of gold leaf hung in contact with each other from the end of a conductor. When excited they diverge. The leaves are enclosed in a glass vessel. Fig. 160. GOLD LEAF ELECTROSCOPE. 234 STANDARD ELECTRICAL DICTIONARY. Electroscope, Pith Ball. Two pith balls suspended at opposite ends of a silk thread doubled in the middle. When charged with like electricity they repel each other. The extent of their repulsion indicates the potential of their charge. Electrostatic Attraction and Repulsion. The attraction and repulsion of electrostatically charged bodies for each other, shown when charged with electricity. If charged with electricity of the same sign they repel each other. If with opposite they attract each other. The classic attraction and subsequent repulsion of bits of straw and chaff by the excited piece of amber is a case of electrostatic attraction and repulsion. (See Electricity, Static--Electrostatics--Coulomb's Laws of Electrostatic Attraction and Repulsion.) Electrostatic Induction, Coefficient of. The coefficient expressing the ratio of the charge or change of charge developed in one body to the potential of the inducing body. Electrostatic Lines of Force. Lines of force assumed to exist in an electrostatic field of force, and to constitute the same. In general they correspond in action and attributes with elcctro-magnetic lines of force. They involve in almost all cases either a continuous circuit, or a termination at both ends in oppositely charged surfaces. Fig. 161. ELECTROSTATIC LINES OF FORCE BETWEEN NEAR SURFACES. Fig. 162. ELECTROSTATIC LINKS OF FORCE BETWEEN DISTANT SURFACES. 235 STANDARD ELECTRICAL DICTIONARY. The cut, Fig. 161, shows the general course taken by lines of force between two excited surfaces when near together. Here most of them are straight lines reaching straight across from surface to surface, while a few of them arch across from near the edges, tending to spread. If the bodies are drawn apart the spreading tendency increases and the condition of things shown in the next cut, Fig. 162, obtains. There is an axial line whose prolongations may be supposed to extend indefinitely, as occupying a position of unstable equilibrium. Here the existence of a straight and unterminated line of force may be assumed. A direction is predicated to lines of force corresponding with the direction of an electric current. They are assumed to start from a positively charged and to go towards a negatively charged surface. A positively charged body placed in an electrostatic field of force will be repelled from the region of positive into or towards the region of negative potential following the direction of the lines of force, not moving transversely to them, and having no transverse component in its motion. [Transcriber's note: More precisely, "A positively charged body placed in an electrostatic field of force will be repelled from the region of positive into or towards the region of negative potential ACCELERATING in the direction of the lines of force, not ACCELERATING transversely to them, and having no transverse component in its ACCELERATION." Previously acquired momentum can produce a transverse component of VELOCITY.] Electrostatics. The division of electric science treating of the phenomena of electric charge, or of electricity in repose, as contrasted with electro-dynamics or electricity in motion or in current form. Charges of like sign repel, and of unlike sign attract each other. The general inductive action is explained by the use of the electrostatic field of force and electrostatic lines of force, q. v. The force of attraction and repulsion of small bodies or virtual points, which are near enough to each other, vary as the square of the distance nearly, and with the product of the quantities of the charges of the two bodies. Electrostatic Refraction. Dr. Kerr found that certain dielectrics exposed to electric strain by being placed between two oppositely excited poles of a Holtz machine or other source of very high tension possess double refracting powers, in other words can rotate a beam of polarized light, or can develop two complimentary beams from common light. Bisulphide of carbon shows the phenomenon well, acting as glass would if the glass were stretched in the direction of the electrostatic lines of force. To try it with glass, holes are drilled in a plate and wires from an influence machine are inserted therein. The discharge being maintained through the glass it polarizes light. Synonym--Kerr Effect. Electrostatic Series. A table of substances arranged in the order in which they are electrostatically charged by contact, generally by rubbing against each other. The following series is due to Faraday. The first members become positively excited when rubbed with any of the following members, and vice versa. The first elements correspond to the carbon plate in a galvanic battery, the succeeding elements to the zinc plate. Cat, and Bear-skin--Flannel--Ivory--Feathers--Rock Crystal--Flint Glass--Cotton--Linen--Canvas--White Silk--the Hand--Wood--Shellac--the Metals (Iron-Copper-Brass-Tin-Silver-Platinum)--Sulphur. There are some irregularities. A feather lightly drawn over canvas is negatively electrified; if drawn through folds pressed against it it is positively excited. Many other exceptions exist, so that the table is of little value. 236 STANDARD ELECTRICAL DICTIONARY. Electrostatic Stress. The stress produced upon a transparent medium in an electrostatic field of force by which it acquires double refracting or polarizing properties as regards the action of such medium upon light. (See Electrostatic Refraction.) Electro-therapeutics or Therapy. The science treating of the effects of electricity upon the animal system in the treatment and diagnosis of disease. Electrotonus. An altered condition of functional activity occurring in a nerve subjected to the passage of an electric current. If the activity is decreased, which occurs near the anode, the state is one of anelectrotonus, if the activity is increased which occurs near the kathode the condition is one of kathelectrotonus. Electrotype. The reproduction of a form of type or of an engraving or of the like by electroplating, for printing purposes. The form of type is pressed upon a surface of wax contained in a shallow box. The wax is mixed with plumbago, and if necessary some more is dusted and brushed over its surface and some iron dust is sprinkled over it also. A matrix or impression of the type is thus obtained, on which copper is deposited by electroplating, q. v. Element, Chemical. The original forms of matter that cannot be separated into constituents by any known process. They are about seventy in number. Some of the rarer ones are being added to or cancelled with the progress of chemical discovery. For their electric relations see Electro-chemical Equivalents--Electro-chemical Series. The elements in entering into combination satisfy chemical affinity and liberate energy, which may take the form of electric energy as in the galvanic battery, or of heat energy, as in the combustion of carbon or magnesium. Therefore an uncombined element is the seat of potential energy. (See Energy, Potential.) In combining the elements always combine in definite proportions. A series of numbers, one being proper to each element which denote the smallest common multipliers of these proportions, are called equivalents. Taking the theory of valency into consideration the product of the equivalents by the valencies gives the atomic weights. 237 STANDARD ELECTRICAL DICTIONARY. Element, Mathematical. A very small part of anything, corresponding in a general way to a differential, as the element of a current. Element of a Battery Cell. The plates in a galvanic couple are termed elements, as the carbon and zinc plates in a Bunsen cell. The plate unattacked by the solution, as the carbon plate in the above battery, is termed the negative plate or element; the one attacked, as the zinc plate, is termed the positive plate or element. Synonym--Voltaic Element. Elements, Electrical Classification of. This may refer to Electro-chemical Series, Electrostatic Series, or Thermo-electric Series, all of which may be referred to. Element, Thermo-electric. One of the metals or other conductors making a thermo-electric couple, the heating of whose junction produces electro-motive force and a current, if on closed circuit. The elements of a couple are respectively positive and negative, and most conductors can be arranged in a series according to their relative polarity. (See Thermo-electric Series.) Elongation. The throw of the magnetic needle. (See Throw.) Synonym--Throw. Embosser, Telegraph. A telegraphic receiver giving raised characters on a piece of paper. It generally refers to an apparatus of the old Morse receiver type, one using a dry point stylus, which pressing the paper into a groove in the roller above the paper, gave raised characters in dots and lines. Fig. 163. MORSE RECEIVER. 238 STANDARD ELECTRICAL DICTIONARY. E. M. D. P. Abbreviation for "electro-motive difference of potential" or for electro-motive force producing a current as distinguished from mere inert potential difference. E. M. F. Abbreviation for "electro-motive force." Fig. 164. END-ON METHOD. End-on Method. A method of determining the magnetic moment of a magnet. The magnet under examination, N S, is placed at right angles to the magnetic meridian, M O R, and pointing directly at or "end on" to the centre of a compass needle, n s. From the deflection a of the latter the moment is calculated. Endosmose, Electric. The inflowing current of electric osmose. (See Osmose, Electric.) End Play. The power to move horizontally in its bearings sometimes given to armature shafts. This secures a more even wearing of the commutator faces. End play is not permissible in disc armatures, as the attraction of the field upon the face of the armature core would displace it endwise. For such armatures thrust-bearings preventing end play have to be provided. Energy. The capacity for doing work. It is measured by work units which involve the exercise of force along a path of some length. A foot-pound, centimeter-gram, and centimeter-dyne are units of energy and work. The absolute unit of energy is the erg, a force of one dyne exercised over one centimeter of space. (See Dyne.) The dimensions of energy are force (M * L / T^2) * space (L) = M * (L^2 / T^2). Energy may be chemical (atomic or molecular), mechanical, electrical, thermal, physical, potential, kinetic, or actual, and other divisions could be formulated. 239 STANDARD ELECTRICAL DICTIONARY. Energy, Atomic. The potential energy due to atomic relations set free by atomic change; a form of chemical energy, because chemistry refers to molecular as well as to atomic changes. When atomic energy loses the potential form it immediately manifests itself in some other form, such as heat or electric energy. It may be considered as always being potential energy. (See Energy, Chemical.) [Transcriber's note: This item refers to chemical energy, that is manifest in work done by electric forces during re-arrangement of electrons. Atomic energy now refers to re-arrangement of nucleons (protons and neutrons) and the resulting conversion of mass into energy.] Energy, Chemical. A form of potential energy (see Energy, Potential) possessed by elements in virtue of their power of combining with liberation of energy, as in the combination of carbon with oxygen in a furnace; or by compounds in virtue of their power of entering into other combinations more satisfying to the affinities of their respective elements or to their own molecular affinity. Thus in a galvanic couple water is decomposed with absorption of energy, but its oxygen combines with zinc with evolution of greater amount of energy, so that in a voltaic couple the net result is the setting free of chemical energy, which is at once converted into electrical energy in current form, if the battery is on a closed circuit. Energy, Conservation of. A doctrine accepted as true that the sum of energy in the universe is fixed and invariable. This precludes the possibility of perpetual motion. Energy may be unavailable to man, and in the universe the available energy is continually decreasing, but the total energy is the same and never changes. [Transcriber's note: If mass is counted a energy (E=m*(c^2)) then energy is strictly conserved.] Energy, Degradation of. The reduction of energy to forms in which it cannot be utilized by man. It involves the reduction of potential energy to kinetic energy, and the reduction of kinetic energy of different degrees to energy of the same degree. Thus when the whole universe shall have attained the same temperature its energy will have become degraded or non-available. At present in the sun we have a source of kinetic energy of high degree, in coal a source of potential energy. The burning of all the coal will be an example of the reduction of potential to kinetic energy, and the cooling of the sun will illustrate the lowering in degree of kinetic energy. (See Energy, Conservation of--Energy, Potential--Energy, Kinetic.) Energy, Electric. The capacity for doing work possessed by electricity under proper conditions. Electric energy may be either kinetic or potential. As ordinary mechanical energy is a product of force and space, so electric energy is a product of potential difference and quantity. Thus a given number of coulombs of electricity in falling a given number of volts develop electric energy. The dimensions are found therefore by multiplying electric current intensity quantity ((M^.5) * (L^.5)), by electric potential ((M^.5)*(L^1.5) / (T^2)), giving (M * (L^2)/(T^2)), the dimensions of energy in general as it should be. The absolute unit of electric energy in electro-magnetic measure is (1E-7) volt coulombs. 240 STANDARD ELECTRICAL DICTIONARY. The practical unit is the volt-coulomb. As the volt is equal to 1E8 absolute units of potential and the coulomb to 0.1 absolute units of quantity, the volt-coulomb is equal to 1E7 absolute units of energy. The volt-coulomb is very seldom used, and the unit of Electric Activity or Power (see Power, Electric), the volt-ampere, is universally used. This unit is sometimes called the Watt, q. v., and it indicates the rate of expenditure or of production of electric energy. The storing up in a static accumulator or condenser of a given charge of electricity, available for use with a given change of potential represents potential electric energy. The passing of a given quantity through a conductor with a given fall of potential represents kinetic electric energy. In a secondary battery there is no storage of energy, but the charging current simply accumulates potential chemical energy in the battery, which chemical energy is converted into electric energy in the discharge or delivery of the battery. It is customary to discuss Ohm's law in this connection; it is properly treated under Electric Power, to which the reader is referred. (See Power, Electric.) [Transcriber's note: A volt-ampere or watt is a unit of power. A volt-coulomb second or watt-second is a unit of energy. Power multiplied by time yields energy.] Energy, Electric Transmission of. If an electric current passes through a conductor all its energy is expended in the full circuit. Part of the circuit may be an electrical generator that supplies energy as fast as expended. Part of the circuit may be a motor which absorbs part of the energy, the rest being expended in forcing a current through the connecting wires and through the generator. The electric energy in the generator and connecting wires is uselessly expended by conversion into heat. That in the motor in great part is utilized by conversion into mechanical energy which can do useful work. This represents the transmission of energy. Every electric current system represents this operation, but the term is usually restricted to the transmission of comparatively large quantities of energy. A typical installation might be represented thus. At a waterfall a turbine water wheel is established which drives a dynamo. From the dynamo wires are carried to a distant factory, where a motor or several motors are established, which receive current from the dynamo and drive the machinery. The same current, if there is enough energy, may be used for running lamps or electroplating. As electric energy (see Energy, Electric,) is measured by the product of potential difference by quantity, a very small wire will suffice for the transmission of a small current at a high potential, giving a comparatively large quantity of energy. It is calculated that the energy of Niagara Falls could be transmitted through a circuit of iron telegraph wire a distance of over 1,000 miles, but a potential difference of 135,000,000 volts would be required, something quite impossible to obtain or manage. [Transcriber's note: Contemporary long distance power transmission lines use 115,000 to 1,200,000 volts. At higher voltages corona discharges (arcing) create unacceptable losses.] 241 STANDARD ELECTRICAL DICTIONARY. Energy, Kinetic. Energy due to matter being actually in motion. It is sometimes called actual energy. The energy varies directly with the mass and with the square of the velocity. It is represented in formula by .5 *M * (v^2). Synonyms--Actual Energy--Energy of Motion--Dynamic Energy. Energy, Mechanical. The energy due to mechanical change or motion, virtually the same as molar energy. (See Energy, Molar.) Energy, Molar. The energy of masses of matter due to movements of or positions of matter in masses; such as the kinetic energy of a pound or of a ton in motion, or the potential energy of a pound at an elevation of one hundred feet. Energy, Molecular. The potential energy due to the relations of molecules and set free by their change in the way of combination. It is potential for the same reason that applies to atomic and chemical energy, of which latter it is often a form, although it is often physical energy. The potential energy stored up in vaporization is physical and molecular energy; the potential energy stored up in uncombined potassium oxide and water, or calcium oxide (quicklime) and water is molecular, and when either two substances are brought together kinetic, thermal or heat energy is set free, as in slaking lime for mortar. Energy of an Electrified Body. An electrified body implies the other two elements of a condenser. It is the seat of energy set free when discharged. (See Dielectric, Energy of.) The two oppositely charged bodies tend to approach. This tendency, together with the distances separating them, represents a potential energy. Energy of Stress. Potential energy due to stress, as the stretching of a spring. This is hardly a form of potential energy. A stressed spring is merely in a position to do work at the expense of its own thermal or kinetic energy because it is cooled in doing work. If it possessed true potential energy of stress it would not be so cooled. Energy of Position. Potential energy due to position, as the potential energy of a pound weight raised ten feet (ten foot lbs.). (See Energy, Potential.) Energy, Physical. The potential energy stored up in physical position or set free in physical change. Thus a vapor or gas absorbs energy in its vaporization, which is potential energy, and appears as heat energy when the vapor liquefies. 242 STANDARD ELECTRICAL DICTIONARY. Energy, Potential, or Static Energy. The capacity for doing work in a system due to advantage of position or other cause, such as the stress of a spring. A pound weight supported ten feet above a plane has ten foot lbs. of potential energy of position referred to that plane. A given weight of an elementary substance represents potential chemical energy, which will be liberated as actual energy in its combination with some other element for which it has an affinity. Thus a ton of coal represents a quantity of potential chemical energy which appears in the kinetic form of thermal energy when the coal is burning in a furnace. A charged Leyden jar represents a source of potential electric energy, which becomes kinetic heat energy as the same is discharged. Energy, Thermal. A form of kinetic molecular energy due to the molecular motion of bodies caused by heat. Entropy. Non-available energy. As energy may in some way or other be generally reduced to heat, it will be found that the equalizing of temperature, actual and potential, in a system, while it leaves the total energy unchanged, makes it all unavailable, because all work represents a fall in degree of energy or a fall in temperature. But in a system such as described no such fall could occur, therefore no work could be done. The universe is obviously tending in that direction. On the earth the exhaustion of coal is in the direction of degradation of its high potential energy, so that the entropy of the universe tends to zero. (See Energy, Degradation of.) [Transcriber's note: Entropy (disorder) INCREASES, while AVAILABLE ENERGY tends to zero.] Entropy, Electric. Clerk Maxwell thought it possible to recognize in the Peltier effect, q. v., a change in entropy, a gain or loss according to whether the thermo-electric junction was heated or cooled. This is termed Electric Entropy. (See Energy, Degradation of.) 243 STANDARD ELECTRICAL DICTIONARY. Fig. 165. EPINUS' CONDENSER, Epinus' Condenser. Two circular brass plates, A and B, are mounted on insulating supports, and arranged to be moved towards or away from each other as desired. Between them is a plate of glass, C, or other dielectric. Pith balls may be suspended back of each brass plate as shown. The apparatus is charged by connecting one plate to an electric machine and the other to the earth. The capacity of the plate connected to the machine is increased by bringing near to it the grounded plate, by virtue of the principle of bound charges. This apparatus is used to illustrate the principles of the electric condenser. It was invented after the Leyden jar was invented. Fig. 166. EPINUS' CONDENSER. E. P. S. Initials of Electrical Power Storage; applied to a type of secondary battery made by a company bearing that title. Fig. 167. CAM EQUALIZER. 244 STANDARD ELECTRICAL DICTIONARY. Equalizer. In electro-magnetic mechanism an arrangement for converting the pull of the electro-magnet varying in intensity greatly over its range of action, into a pull of sensibly equal strength throughout. The use of a rocking lever acting as a cam, with leverage varying as the armature approaches or recedes from the magnet core is one method of effecting the result. Such is shown in the cut. E is an electro-magnet, with armature a. A and B are the equalizer cams. The pull on the short end of the cam B is sensibly equal for its whole length. Many other methods have been devised, involving different shapes of pole pieces, armatures or mechanical devices other than the one just shown. Equipotential. adj. Equal in potential; generally applied to surfaces. Thus every magnetic field is assumed to be made up of lines of force and intersecting those lines, surfaces, plane, or more or less curved in contour, can be determined, over all parts of each one of which the magnetic intensity will be identical. Each surface is the locus of equal intensity. The same type of surface can be constructed for any field of force, such as an electrostatic field, and is termed an equipotential surface. Equipotential Surface, Electrostatic. A surface in an electrostatic field of force, which is the locus of all points of a given potential in such field; a surface cutting all the lines of force at a point of identical potential. Lines of force are cut perpendicularly by an equipotential surface, or are normal thereto. Equipotential Surface, Magnetic and Electro-magnetic. A surface bearing the same relation to a magnetic or electro-magnetic field of force that an electrostatic equipotential surface (see Equipotential Surface, Electrostatic,) does to an electrostatic field of force. Equivalent, Chemical. The quotient obtained by dividing the atomic weight of an element by its valency. Equivalents, Electro-chemical. The weight of any substance set free by one coulomb of electricity. The following give some equivalents expressed in milligrams: Hydrogen .0105 Mercury (mercurous) 2.10 Gold .6877 Iron (ferric) .1964 Silver 1.134 Iron (ferrous) .294 Copper (cupric) .3307 Nickel .3098 Mercury (mercuric) 1.05 Zinc .3413 Lead 1.0868 Chlorine .3728 Oxygen .89 245 STANDARD ELECTRICAL DICTIONARY. Equivalent, Electro-mechanical. The work or energy equivalent to unit quantities of electric energy, q. v.; or equivalent to a unit current in a conductor whose ends differ one unit of potential. The unit of electric energy taken is the watt-second or volt-coulomb. One volt-coulomb is equal to Ergs 1E7 [10000000] Foot Pound .737337 Gram-degree C. .24068 Horse Power Second .0013406 Pound-degree F. .000955 One horse power is equal to 745.943 volt coulombs per second. Equivalent, Electro-thermal. The heat produced by a unit current passing through a conductor with unit difference of potential at its ends; the heat equivalent of a volt-coulomb or watt-second. It is equal to Gram-degree C. .24068 Pound-degree F. .000955 Equivalent, Thermo-chemical. The calories evolved by the combination of one gram of any substance with its equivalent of another substance being determined, the product obtained by multiplying this number by the equivalent (atomic or molecular weight / valency) of the first element or substance is the thermo-chemical equivalent. If expressed in kilogram calories, the product of the thermo-chemical equivalent by 0.43 gives the voltage required to effect such decomposition. The following are thermo-chemical equivalents of a few combinations: Water 34.5 Zinc oxide 43.2 Iron protoxide 34.5 Iron Sesquioxide 31.9 X 3 Copper oxide 19.2 Equivolt. "The mechanical energy of one volt electro-motive force exerted under unit conditions through one equivalent of chemical action in grains." (J. T. Sprague.) This unit is not in general use as the unit of electric energy, the volt-coulomb and (for rate of electric energy) the volt-ampere being always used. Erg. The absolute or fundamental C. G. S. unit of work or energy. The work done or energy expended in moving a body through one centimeter against a resistance of one dyne. Erg-ten. Ten millions of ergs, or ten meg-ergs. Escape. A term applied to leakage of current. Etching, Electric. A process of producing an etched plate. The plate is coated with wax, and the design traced through as in common etching. It is then placed in a bath and is connected to the positive terminal from a generator, whose negative is immersed in the same bath, so that the metal is dissolved by electrolytic action. By attaching to the other terminal and using a plating bath, a rough relief plate may be secured, by deposition in the lines of metal by electroplating. Synonym--Electric Engraving. 246 STANDARD ELECTRICAL DICTIONARY. Ether. The ether is a hypothetical thing that was invented to explain the phenomena of light. Light is theoretically due to transverse vibrations of the ether. Since the days of Young the conception of the ether has extended, and now light, "radiant heat," and electricity are all treated as phenomena of the ether. Electrical attraction and repulsion are explained by considering them due to local stresses in the ether; magnetic phenomena as due to local whirlpools therein. The ether was originally called the luminiferous ether, but the adjective should now be dropped. Its density is put at 936E-21 that of water, or equal to that of the atmosphere at 210 miles above the earth's surface. Its rigidity is about 1E-9 that of steel (see Ten, Powers of); as a whole it is comparable to an all-pervading jelly, with almost perfect elasticity. The most complete vacuum is filled with ether. All this is a hypothesis, for the ether has never been proved to exist. Whether gravitation will ever be explained by It remains to be seen. [Transcriber's note: The Michelson-Morley experiment in 1887 (five years before this book) cast serious doubt on the ether. In 1905 Einstein explained electromagnetic phenomenon with photons. In 1963 Edward M. Purcell used special relativity to derive the existence of magnetism and radiation.] Eudiometer. A graduated glass tube for measuring the volumes of gases. In its simplest form it is simply a cylindrical tube, with a scale etched or engraved upon it, closed at one end and open at the other. The gas to be measured is collected in it over a liquid, generally water, dilute sulphuric acid in the gas voltameter, or mercury. Many different shapes have been given them by Hoffmann, Ure, Bunsen and others. Evaporation, Electric. The superficial sublimation or evaporation of a substance under the influence of negative electricity. It is one of the effects investigated by Crookes in his experiments with high vacua. He found that when a metal, even so infusible as platinum, was exposed to negative electrification in one of his high vacuum tubes, that it was volatilized perceptibly. A cadmium electrode heated and electrified negatively was found to give a strong coating of metal on the walls of the tube. Even in the open air the evaporation of water was found to be accelerated by negative electrification. Exchange, Telephone. The office to which telephone wires lead in a general telephone system. In the office by a multiple switch board, or other means, the different telephones are interconnected by the office attendants, so that any customers who desire it may be put into communication with each other. The exchange is often termed the Central Office, although it may be only a branch office. Excitability, Faradic. The action produced in nerve or muscle of the a