Hydrogen .0105 Mercury (mercurous) 2.10Gold .6877 Iron (ferric) .1964Silver 1.134 Iron (ferrous) .294Copper (cupric) .3307 Nickel .3098Mercury (mercuric) 1.05 Zinc .3413Lead 1.0868 Chlorine .3728Oxygen .89245 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 oneunit of potential. The unit of electric energy taken is the watt-secondor volt-coulomb. One volt-coulomb is equal toErgs 1E7 [10000000]Foot Pound .737337Gram-degree C. .24068Horse Power Second .0013406Pound-degree F. .000955One 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 withunit difference of potential at its ends; the heat equivalent of avolt-coulomb or watt-second. It is equal toGram-degree C. .24068Pound-degree F. .000955Equivalent, Thermo-chemical.The calories evolved by the combination of one gram of any substancewith its equivalent of another substance being determined, the productobtained by multiplying this number by the equivalent (atomic ormolecular weight / valency) of the first element or substance is thethermo-chemical equivalent. If expressed in kilogram calories, theproduct of the thermo-chemical equivalent by 0.43 gives the voltagerequired to effect such decomposition.The following are thermo-chemical equivalents of a few combinations:Water 34.5Zinc oxide 43.2Iron protoxide 34.5Iron Sesquioxide 31.9 X 3Copper oxide 19.2Equivolt."The mechanical energy of one volt electro-motive force exerted underunit conditions through one equivalent of chemical action in grains."(J. T. Sprague.) This unit is not in general use as the unit of electricenergy, the volt-coulomb and (for rate of electric energy) thevolt-ampere being always used.Erg.The absolute or fundamental C. G. S. unit of work or energy. The workdone or energy expended in moving a body through one centimeter againsta 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 ina bath and is connected to the positive terminal from a generator, whosenegative is immersed in the same bath, so that the metal is dissolved byelectrolytic action. By attaching to the other terminal and using aplating bath, a rough relief plate may be secured, by deposition in thelines of metal by electroplating.Synonym--Electric Engraving.246 STANDARD ELECTRICAL DICTIONARY.Ether.The ether is a hypothetical thing that was invented to explain thephenomena of light. Light is theoretically due to transverse vibrationsof the ether. Since the days of Young the conception of the ether hasextended, and now light, "radiant heat," and electricity are all treatedas phenomena of the ether. Electrical attraction and repulsion areexplained by considering them due to local stresses in the ether;magnetic phenomena as due to local whirlpools therein. The ether wasoriginally called the luminiferous ether, but the adjective should nowbe dropped. Its density is put at 936E-21 that of water, or equal tothat of the atmosphere at 210 miles above the earth's surface. Itsrigidity is about 1E-9 that of steel (see Ten, Powers of); as a whole itis 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 yearsbefore this book) cast serious doubt on the ether. In 1905 Einsteinexplained electromagnetic phenomenon with photons. In 1963 Edward M.Purcell used special relativity to derive the existence of magnetism andradiation.]Eudiometer.A graduated glass tube for measuring the volumes of gases. In itssimplest form it is simply a cylindrical tube, with a scale etched orengraved upon it, closed at one end and open at the other. The gas to bemeasured is collected in it over a liquid, generally water, dilutesulphuric acid in the gas voltameter, or mercury. Many different shapeshave been given them by Hoffmann, Ure, Bunsen and others.Evaporation, Electric.The superficial sublimation or evaporation of a substance under theinfluence of negative electricity. It is one of the effects investigatedby Crookes in his experiments with high vacua. He found that when ametal, even so infusible as platinum, was exposed to negativeelectrification in one of his high vacuum tubes, that it was volatilizedperceptibly. A cadmium electrode heated and electrified negatively wasfound to give a strong coating of metal on the walls of the tube. Evenin the open air the evaporation of water was found to be accelerated bynegative 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 differenttelephones are interconnected by the office attendants, so that anycustomers who desire it may be put into communication with each other.The exchange is often termed the Central Office, although it may be onlya branch office.Excitability, Faradic.The action produced in nerve or muscle of the animal system by analternating or intermitting high potential discharge from an inductioncoil.247 STANDARD ELECTRICAL DICTIONARY.Excitability, Galvanic.The same as Faradic excitability, except that it refers to the effectsof the current from a galvanic battery.Excitability of Animal System, Electric.The susceptibility of a nerve or muscle to electric current shown by theeffect produced by its application.Exciter.A generator used for exciting the field magnet of a dynamo. Inalternating current dynamos, e. g., of the Westinghouse type, a specialdynamo is used simply to excite the field magnet. In central stationdistribution the same is often done for direct current dynamos.Exosmose, Electric.The outflowing current of electric osmose. (See Osmose, Electric.)Expansion, Coefficient of.The number expressing the proportional increase in size, either length,area or volume, of a substance under the influence generally of heat.There are three sets of coefficients, (1) of linear expansion, (2) ofsuperficial expansion, (3) of cubic expansion or expansion of volume.The first and third are the only ones much used. They vary for differentsubstances, and for the same substance at different temperatures. Theyare usually expressed as decimals indicating the mixed number referredto the length or volume of the body at the freezing point as unity.Expansion, Electric.(a) The increase in volume of a condenser, when chargedelectrostatically. A Leyden jar expands when charged, and contracts whendischarged.(b) The increase in length of a bar of iron when magnetized.This is more properly called magnetic expansion or magnetic elongation.Exploder.(a) A small magneto-generator for producing a current for heating thewire in an electric fuse of the Abel type (see Fuse, Electric), andthereby determining an explosion.(b) The term may also be applied to a small frictional or influencemachine for producing a spark for exploding a spark fuse.Explorer.A coil, similar to a magnetizing coil (see Coil, Magnetizing), used forinvestigating the electro-magnetic circuit and for similar purposes. Ifplaced around an electro-magnet and connected with a galvanometer, itwill produce a deflection, owing to a momentary induced current, uponany change in the magnet, such as removing or replacing the armature. Itis useful in determining the leakage of lines of force and for generalinvestigations of that nature. It is often called an exploring coil.Hughes' Induction Balance (see Induction Balance, Hughes') is sometimescalled a Magnetic Explorer. The exploring coil may be put in circuitwith a galvanometer for quantitative measurements or with a telephonefor qualitative ones.248 STANDARD ELECTRICAL DICTIONARY.Extension Bell Call.A system of relay connection, q. v., by which a bell is made to continueringing after the current has ceased coming over the main line. It isdesigned to prolong the alarm given by a magneto call bell, q. v., whichlatter only rings as long as the magneto handle is turned. A vibratingelectric bell (see Bell, Electric,) is connected in circuit with a localbattery and a switch normally open, but so constructed as to close thecircuit when a current is passed and continue to do so indefinitely. Thedistant circuit is connected to this switch. When the magneto is workedit acts upon the switch, closes the local battery circuit and leaves itclosed, while the bell goes on ringing until the battery is exhausted orthe switch is opened by hand.Eye, Electro-magnetic.An apparatus used in exploring a field of electro-magnetic radiations.It is a piece of copper wire 2 millimeters (.08 inch) in diameter, bentinto an almost complete circle 70 millimeters (.28 inch) in diameter,with terminals separated by an air gap. This is moved about in theregion under examination, and by the production of a spark indicates thelocality of the loops or venters in systems of stationary waves.