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 iscarried by insulating stem g1. The charging electrode is supported by aninsulating stem g2, and without contact with the box passes out of itscover through a guard tube E, with cover, sometimes called umbrella, V.The umbrella is to protect the apparatus from air currents. At m is thesighting lens. H is a lead box packed with pumice stone, moistened withoil of vitriol or concentrated sulphuric acid, to preserve theatmosphere dry. Before use the acid is boiled with some ammoniumsulphate to expel any corrosive nitrogen oxides, which might corrode thebrass.In use the upper disc is charged by its insulated electrode within thetube E; the movable disc is charged if desired directly through the caseof the instrument. The upper disc is screwed up or down by themicrometer head M, until the sighted position is reached. The readingsof 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 containsmercury; its end drawn out to a fine aperture dips into a vessel B whichcontains dilute sulphuric acid with mercury under it, as shown. Wiresrunning from the binding-posts a and b connect one with the mercury inA, the other with that in B. The upper end of the tube A connects with athick rubber mercury reservoir T, and manometer H. The surface tensionof the mercury-acid film at the lower end of the tube A keeps all inequilibrium. If now a potential difference is established between a andb, as by connecting a battery thereto, the surface tension is increasedand the mercury rises in the tube B. By screwing down the compressingclamp E, the mercury is brought back to its original position. Themicroscope M is used to determine this position with accuracy. Thechange in reading of the manometer gives the relation of change ofsurface tension and therefore of potential. Each electrometer needsspecial graduation or calibration, but is exceedingly sensitive andaccurate. It cannot be used for greater potential differences than .6volt, but can measure .0006 volt. Its electrostatic capacity is so smallthat it can indicate rapid changes. Another form indicates potentialdifference by the movement of a drop of sulphuric acid in a horizontalglass tube, otherwise filled with mercury, and whose ends lead into twomercury cups or reservoirs. The pair of electrodes to be tested areconnected to the mercury vessels. The drop moves towards the negativepole, and its movement for small potential differences (less than onevolt) is proportional to the electro-motive force or potentialdifference.226 STANDARD ELECTRICAL DICTIONARY.Electrometer Gauge.An absolute electrometer (see Electrometer, Absolute) forming anattachment to a Thomson quadrant electrometer. It is used to test thepotential of the flat needle connected with the inner surface of theLeyden jar condenser of the apparatus. This it does by measuring theattraction between itself and an attracting disc, the latter connectedby a conductor with the interior of the jar.Electrometer, Lane's.A Leyden jar with mounted discharger, so that when charged to a certainpoint it discharges itself. It is connected with one coating of any jarwhose charge is to be measured, which jar is then charged by the othercoating. As the jar under trial becomes charged to a certain point theelectrometer jar discharges itself, and the number of discharges is themeasure 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 shownin 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 eachother, but the opposite ones connect with each other by wires. Theapparatus is adjusted so that, when the quadrants are in an unexcitedcondition the needle is at rest over one of the diametrical divisionsbetween quadrants. The needle by its suspension wire is in communicationwith the interior of a Leyden jar which is charged. The whole is coveredwith a glass shade, and the air within is kept dry by a dish ofconcentrated sulphuric acid so that the jar retains its charge for along time and keeps the needle at approximately a constant potential. Ifnow two pairs of quadrants are excited with opposite electricities, aswhen connected with the opposite poles of an insulated galvanic cell,the needle is repelled by one pair and attracted by the other, andtherefore rotates through an arc of greater or less extent. A smallconcave mirror is attached above the needle and its image is reflectedon 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 ofan electric machine, for roughly indicating the relative potentialthereof. It consists of a wooden standard attached perpendicularly tothe conductor. Near one end is attached a semi-circular or quadrant arcof a circle graduated into degrees or angular divisions. An index,consisting of a straw with a pith-bell attached to its end hangs fromthe center of curvature of the arc. When the prime conductor is chargedthe index moves up over the scale and its extent of motion indicates thepotential relatively.When the "quadrant electrometer" is spoken of it may always be assumedthat Sir William Thomson's instrument is alluded to. Henley's instrumentis properly termed a quadrant electroscope. (See Electroscope.)Electro-motive Force.The cause which produces currents of electricity. In general it can beexpressed in difference of potentials, although the term electro-motiveforce should be restricted to potential difference causing a current. Itis often a sustained charging of the generator terminals whence thecurrent 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 isoften 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 casesvirtually identical, and distinctions drawn between them vary withdifferent authors. If we consider a closed electric circuit carrying acurrent, a definite electro-motive force determined by Ohm's law fromthe resistance and current obtains in it. But if we attempt to definepotential difference as proper to the circuit we may quite fail.Potential difference in a circuit is the difference in potential betweendefined points of such circuit. But no points in a closed circuit can befound which differ in potential by an amount equal to the entireelectro-motive force of the circuit. Potential difference is properlythe measure of electro-motive force expended on the portion of a circuitbetween any given points. Electro-motive force of an entire circuit, asit is measured, as it were, between two consecutive points but aroundthe long portion of the circuit, is not conceivable as merely potentialdifference. Taking the circle divided in to degrees as an analogy, theelectro-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 differencebetween the same two points would be only 1º, for it would be measuredby the nearest path.[Transcriber's notes: If 360º is the "long" way, 0º is the "short". Aformal restatement of the above definition of EMF: "If a charge Q passesthrough a device and gains energy U, the net EMF for that device is theenergy gained per unit charge, or U/Q. The unit of EMF is a volt, ornewton-meter per coulomb."]228 STANDARD ELECTRICAL DICTIONARY.Electro-motive Force, Counter.A current going through a circuit often has not only true or ohmicresistance to overcome, but meets an opposing E. M. F. This is termedcounter-electro-motive force. It is often treated in calculations asresistance, and is termed spurious resistance. It may be a part of theimpedance of a circuit.In a primary battery hydrogen accumulating on the negative platedevelops counter E. M. F. In the voltaic arc the differential heating ofthe two carbons does the same. The storage battery is changed by acurrent 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 movingthrough a magnetic field at such a rate as to cut one unit line of forceper second. It is that which must be maintained in a circuit of unitresistance to maintain a current of unit quantity therein. It is thatwhich must be maintained between the ends of a conductor in order thatunit current may do unit work in a second.Electro-motive Intensity.The force acting upon a unit charge of electricity. The mean force isequal to the difference of potential between two points within the fieldsituated one centimeter apart, such distance being measured along thelines of force. The term is due to J. Clerk Maxwell.Electro-motive Series.Arrangement of the metals and carbon in series with the mostelectro-positive at one end, and electronegative at the other end. Thefollowing are examples for different exciting liquids:Dilute Sulphuric Dilute Hydrochloric Caustic PotassiumAcid Acid. Potash. Sulphide.Zinc Zinc Zinc ZincCadmium Cadmium Tin CopperTin Tin Cadmium CadmiumLead Lead Antimony TinIron Iron Lead SilverNickel Copper Bismuth AntimonyBismuth Bismuth Iron LeadAntimony Nickel Copper BismuthCopper Silver Nickel NickelSilver Antimony Silver IronGoldPlatinumCarbonIn each series the upper metal is the positive, dissolved or attackedelement.229 STANDARD ELECTRICAL DICTIONARY.Electro-motograph.An invention of Thomas A. Edison. A cylinder of chalk, moistened withsolution of caustic soda, is mounted so as to be rotated by a handle. Adiaphragm has an arm connected to its center. This arm is pressedagainst the surface of the cylinder by a spring. When the cylinder isrotated, a constant tension is exerted on the diaphragm. If a current ispassed through the junction of arm and cylinder the electrolytic actionalters the friction so as to change the stress upon the diaphragm.If the current producing this effect is of the type produced by thehuman voice through a microphone the successive variations in strainupon the diaphragm will cause it to emit articulate sounds. These areproduced directly by the movement of the cylinder, the electrolyticaction being rather the regulating portion of the operation. Hence veryloud sounds can be produced by it. This has given it the name of theloud- speaking telephone.The same principle may be applied in other ways. But the practicalapplication of the motograph is in the telephone described.Fig. 158. ELECTRO-MOTOGRAPH TELEPHONEElectro-motor.This term is sometimes applied to a current generator, such as a voltaicbattery.Electro-muscular Excitation.A term in medical electricity indicating the excitation of muscle as theeffect of electric currents of any kind.Electro-negative. adj.Appertaining to negative electrification; thus of the elements oxygen isthe most electro-negative, because if separated by electrolytic actionfrom 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 lightand electricity. Both are supposed to be phenomena of or due to theluminiferous 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 whichit is exposed (see Selenium);(d) The relation of the index of refraction of a dielectric to thedielectric constant (see Electro-magnetic Theory of Light);(e) The identity (approximate) of the velocity of light in centimetersand the relative values of the electrostatic and electro-magnet unitsof intensity, the latter being 30,000,000,000 times greater than theformer, while the velocity of light is 30,000,000,000 centimeters persecond.Electrophoric Action.The action of an electrophorous; utilized in influence machines. (SeeElectrophorous.)Fig. 159. ELECTROPHOROUS.Electrophorous.An apparatus for the production of electric charges of high potential byelectrostatic induction, q. v. It consists of a disc of insulatingmaterial B, such as resin or gutta percha, which is held in a shallowmetal-lined box or form. The disc may be half an inch thick and a footor 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 beof glass, or simply silk suspension strings. To use it the disc B isexcited by friction with a cat-skin or other suitable substance. Themetallic 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 toroughness there is little real electric contact between the metal anddielectric. On touching the metal disc a quantity of negativeelectricity escapes to the earth. On raising it from the cake it comesoff excited positively, and gives a spark and is discharged. It can bereplaced, touched, removed and another spark can be taken from it, andso on as long as the cake stays charged.The successive discharges represent electrical energy expended. This isderived from the muscular energy expended by the operator in separatingthe two discs when oppositely excited. As generally used it is thereforean apparatus for converting muscular or mechanical energy into electricenergy.231 STANDARD ELECTRICAL DICTIONARY.Electro-physiology.The science of the electric phenomena of the animal system. It may alsobe extended to include plants. The great discovery of Galvani with thefrog'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 conductingsurface. The simplest system makes the object to be plated the negativeelectrode or plate in a galvanic couple. Thus a spoon or other objectmay be connected by a wire to a plate of zinc. A porous cup is placedinside a battery jar. The spoon is placed in the porous cup and the zincoutside 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 onthe spoon.A less primitive way is to use a separate battery as the source ofcurrent; to connect to the positive plate by a wire the object to beplated, and a plate of copper, silver, nickel or other metal to theother pole of the battery. On immersing both object and plate (anode) ina bath of proper solution the object will become plated.In general the anode is of the same material as the metal to bedeposited, and dissolving keeps up the strength of the bath. There are agreat many points of technicality involved which cannot be given here.The surface of the immersed object must be conductive. If not a finewire network stretched over it will gradually fill up in the bath andgive a matrix. More generally the surface is made conductive by beingbrushed over with plumbago. This may be followed by a dusting of irondust, followed by immersion in solution ot copper sulphate. This has theeffect of depositing metallic copper over the surface as a starter forthe final coat.Attention must be paid to the perfect cleanliness of the objects, to thecondition of the bath, purity of anodes and current density.Voltaic batteries are largely used for the current as well as speciallow resistance dynamos. Thermo-electric batteries are also used to someextent but not generally.Electro-pneumatic Signals.Signals, such as railroad signals or semaphores, moved by compressedair, which is controlled by valves operated by electricity. The Housetelegraph, which was worked by air controlled by electricity, might comeunder this term, but it is always understood as applied to railroadsignals, or their equivalent.232 STANDARD ELECTRICAL DICTIONARY.Electropoion Fluid.An acid depolarizing solution for use in zinc-carbon couples, such asthe 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 havebeen gradually added. The better way is to use powdered potassiumbichromate, add it to the water first, and then gradually add thesulphuric acid with constant stirring.(b) To three pints of water add five fluid ounces of concentratedsulphuric acid; add six ounces pulverized potassium bichromate.(c) Mix one gallon concentrated sulphuric acid and three gallons ofwater. In a separate vessel dissolve six pounds potassium bichromate intwo gallons of boiling water. Mix the two.The last is the best formula. Always use electropoion fluid cold. (SeeTrouvé'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 mostelectro-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 theanode of a galvanic battery. The kathode is a metal one, covered with awet sponge and applied on the surface near the place of puncture. It isused for treatment of aneurisms or diseased growths, and also forremoval 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 absorbelectric energy. A motor is an example of an electro-receptivemechanism.Electroscope.An apparatus for indicating the presence of an electric charge, and alsofor determining the sign, or whether the charge is positive or negative.The simplest form consists of a thread doubled at its centre and hungtherefrom. On being charged, or on being connected to a charged body thethreads 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 leafelectroscope). To use an electroscope to determine the sign of thecharge it is first slightly charged. The body to be tested is thenapplied to the point of suspension, or other charging point. If at oncefurther repelled the charge of the body is of the same sign as theslight charge first imparted to the electroscope leaves; the leaves asthey become more excited will at once diverge more. If of different signthey will at first approach as their charge is neutralized and willafterwards diverge.The gold-leaf electroscope is generally enclosed in a glass bell jar orflask. Sometimes a pair of posts rise, one on each side, to supplypoints of induction from the earth to intensify the action. (SeeElectrometer, Quadrant--Electroscope, Gold leaf, and others.)233 STANDARD ELECTRICAL DICTIONARY.Electroscope, Bennett's.A gold-leaf electroscope, the suspended leaves of which are contained ina glass shade or vessel of dry air. On the inside of the glass shade aretwo strips of gold leaf, which rise from the lower edge a shortdistance, being pasted to the glass, and connected to the ground. Theseact by induction to increase the sensitiveness of the instruments.Electroscope, Bohenberger's.A condensing electroscope (see Electroscope, Condensing) with a singlestrip of gold leaf suspended within the glass bell. This is at an equaldistance from the opposite poles of two dry piles (see Zamboni's DryPile) standing on end, one on each side of it. As soon as the leaf isexcited it moves toward one and away from the other pile, and the signof its electrification is shown by the direction of its motion.Electroscope, Condensing.A gold leaf electroscope, the glass bell of which is surmounted by anelectrophorous or static condenser, to the lower plate of which theleaves of gold are suspended or connected.In use the object to be tested is touched to the lower plate, and theupper plate at the same time is touched by the finger. The plates arenow separated. This reduces the capacity of the lower plate greatly andits charge acquires sufficient potential to affect the leaves, althoughthe simple touching may not have affected them at all.Electroscope, Gold Leaf.An electroscope consisting of two leaves of gold leaf hung in contactwith 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 inthe 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 foreach other, shown when charged with electricity. If charged withelectricity of the same sign they repel each other. If with oppositethey attract each other. The classic attraction and subsequent repulsionof bits of straw and chaff by the excited piece of amber is a case ofelectrostatic attraction and repulsion. (See Electricity,Static--Electrostatics--Coulomb's Laws of Electrostatic Attraction andRepulsion.)Electrostatic Induction, Coefficient of.The coefficient expressing the ratio of the charge or change of chargedeveloped 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, andto constitute the same. In general they correspond in action andattributes with elcctro-magnetic lines of force. They involve in almostall cases either a continuous circuit, or a termination at both ends inoppositely charged surfaces.Fig. 161. ELECTROSTATIC LINES OF FORCEBETWEEN NEAR SURFACES.Fig. 162. ELECTROSTATIC LINKS OF FORCEBETWEEN DISTANT SURFACES.235 STANDARD ELECTRICAL DICTIONARY.The cut, Fig. 161, shows the general course taken by lines of forcebetween two excited surfaces when near together. Here most of them arestraight lines reaching straight across from surface to surface, while afew of them arch across from near the edges, tending to spread. If thebodies are drawn apart the spreading tendency increases and thecondition of things shown in the next cut, Fig. 162, obtains. There isan axial line whose prolongations may be supposed to extendindefinitely, as occupying a position of unstable equilibrium. Here theexistence of a straight and unterminated line of force may be assumed.A direction is predicated to lines of force corresponding with thedirection of an electric current. They are assumed to start from apositively charged and to go towards a negatively charged surface. Apositively charged body placed in an electrostatic field of force willbe repelled from the region of positive into or towards the region ofnegative potential following the direction of the lines of force, notmoving transversely to them, and having no transverse component in itsmotion.[Transcriber's note: More precisely, "A positively charged body placedin an electrostatic field of force will be repelled from the region ofpositive into or towards the region of negative potential ACCELERATINGin the direction of the lines of force, not ACCELERATING transversely tothem, and having no transverse component in its ACCELERATION."Previously acquired momentum can produce a transverse component ofVELOCITY.]Electrostatics.The division of electric science treating of the phenomena of electriccharge, or of electricity in repose, as contrasted with electro-dynamicsor electricity in motion or in current form. Charges of like sign repel,and of unlike sign attract each other. The general inductive action isexplained by the use of the electrostatic field of force andelectrostatic lines of force, q. v. The force of attraction andrepulsion of small bodies or virtual points, which are near enough toeach other, vary as the square of the distance nearly, and with theproduct of the quantities of the charges of the two bodies.Electrostatic Refraction.Dr. Kerr found that certain dielectrics exposed to electric strain bybeing placed between two oppositely excited poles of a Holtz machine orother source of very high tension possess double refracting powers, inother words can rotate a beam of polarized light, or can develop twocomplimentary beams from common light. Bisulphide of carbon shows thephenomenon well, acting as glass would if the glass were stretched inthe direction of the electrostatic lines of force. To try it with glass,holes are drilled in a plate and wires from an influence machine areinserted therein. The discharge being maintained through the glass itpolarizes light.Synonym--Kerr Effect.Electrostatic Series.A table of substances arranged in the order in which they areelectrostatically charged by contact, generally by rubbing against eachother. The following series is due to Faraday. The first members becomepositively excited when rubbed with any of the following members, andvice versa. The first elements correspond to the carbon plate in agalvanic battery, the succeeding elements to the zinc plate.Cat, and Bear-skin--Flannel--Ivory--Feathers--Rock Crystal--FlintGlass--Cotton--Linen--Canvas--White Silk--the Hand--Wood--Shellac--theMetals (Iron-Copper-Brass-Tin-Silver-Platinum)--Sulphur. There are someirregularities. A feather lightly drawn over canvas is negativelyelectrified; if drawn through folds pressed against it it is positivelyexcited. Many other exceptions exist, so that the table is of littlevalue.236 STANDARD ELECTRICAL DICTIONARY.Electrostatic Stress.The stress produced upon a transparent medium in an electrostatic fieldof force by which it acquires double refracting or polarizing propertiesas regards the action of such medium upon light. (See ElectrostaticRefraction.)Electro-therapeutics or Therapy.The science treating of the effects of electricity upon the animalsystem in the treatment and diagnosis of disease.Electrotonus.An altered condition of functional activity occurring in a nervesubjected to the passage of an electric current. If the activity isdecreased, which occurs near the anode, the state is one ofanelectrotonus, if the activity is increased which occurs near thekathode the condition is one of kathelectrotonus.Electrotype.The reproduction of a form of type or of an engraving or of the like byelectroplating, for printing purposes. The form of type is pressed upona surface of wax contained in a shallow box. The wax is mixed withplumbago, and if necessary some more is dusted and brushed over itssurface and some iron dust is sprinkled over it also. A matrix orimpression of the type is thus obtained, on which copper is deposited byelectroplating, q. v.Element, Chemical.The original forms of matter that cannot be separated into constituentsby any known process. They are about seventy in number. Some of therarer ones are being added to or cancelled with the progress of chemicaldiscovery. For their electric relations see Electro-chemicalEquivalents--Electro-chemical Series.The elements in entering into combination satisfy chemical affinity andliberate energy, which may take the form of electric energy as in thegalvanic battery, or of heat energy, as in the combustion of carbon ormagnesium. Therefore an uncombined element is the seat of potentialenergy. (See Energy, Potential.) In combining the elements alwayscombine in definite proportions. A series of numbers, one being properto each element which denote the smallest common multipliers of theseproportions, are called equivalents. Taking the theory of valency intoconsideration the product of the equivalents by the valencies gives theatomic weights.237 STANDARD ELECTRICAL DICTIONARY.Element, Mathematical.A very small part of anything, corresponding in a general way to adifferential, as the element of a current.Element of a Battery Cell.The plates in a galvanic couple are termed elements, as the carbon andzinc plates in a Bunsen cell. The plate unattacked by the solution, asthe carbon plate in the above battery, is termed the negative plate orelement; the one attacked, as the zinc plate, is termed the positiveplate or element.Synonym--Voltaic Element.Elements, Electrical Classification of.This may refer to Electro-chemical Series, Electrostatic Series, orThermo-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 acurrent, if on closed circuit. The elements of a couple are respectivelypositive and negative, and most conductors can be arranged in a seriesaccording 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. Itgenerally refers to an apparatus of the old Morse receiver type, oneusing a dry point stylus, which pressing the paper into a groove in theroller 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 forelectro-motive force producing a current as distinguished from mereinert 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 magnetunder examination, N S, is placed at right angles to the magneticmeridian, M O R, and pointing directly at or "end on" to the centre of acompass needle, n s. From the deflection a of the latter the moment iscalculated.Endosmose, Electric.The inflowing current of electric osmose. (See Osmose, Electric.)End Play.The power to move horizontally in its bearings sometimes given toarmature shafts. This secures a more even wearing of the commutatorfaces. End play is not permissible in disc armatures, as the attractionof the field upon the face of the armature core would displace itendwise. For such armatures thrust-bearings preventing end play have tobe provided.Energy.The capacity for doing work. It is measured by work units which involvethe 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 exercisedover one centimeter of space. (See Dyne.)The dimensions of energy areforce (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 otherdivisions 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 wellas to atomic changes. When atomic energy loses the potential form itimmediately manifests itself in some other form, such as heat orelectric energy. It may be considered as always being potential energy.(See Energy, Chemical.)[Transcriber's note: This item refers to chemical energy, that ismanifest in work done by electric forces during re-arrangement ofelectrons. Atomic energy now refers to re-arrangement of nucleons(protons and neutrons) and the resulting conversion of mass intoenergy.]Energy, Chemical.A form of potential energy (see Energy, Potential) possessed by elementsin virtue of their power of combining with liberation of energy, as inthe combination of carbon with oxygen in a furnace; or by compounds invirtue of their power of entering into other combinations moresatisfying to the affinities of their respective elements or to theirown molecular affinity. Thus in a galvanic couple water is decomposedwith absorption of energy, but its oxygen combines with zinc withevolution of greater amount of energy, so that in a voltaic couple thenet result is the setting free of chemical energy, which is at onceconverted into electrical energy in current form, if the battery is on aclosed circuit.Energy, Conservation of.A doctrine accepted as true that the sum of energy in the universe isfixed and invariable. This precludes the possibility of perpetualmotion. Energy may be unavailable to man, and in the universe theavailable energy is continually decreasing, but the total energy is thesame and never changes.[Transcriber's note: If mass is counted a energy (E=m*(c^2)) then energyis 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 thereduction of kinetic energy of different degrees to energy of the samedegree. Thus when the whole universe shall have attained the sametemperature its energy will have become degraded or non-available. Atpresent in the sun we have a source of kinetic energy of high degree, incoal a source of potential energy. The burning of all the coal will bean example of the reduction of potential to kinetic energy, and thecooling of the sun will illustrate the lowering in degree of kineticenergy. (See Energy, Conservation of--Energy, Potential--Energy,Kinetic.)Energy, Electric.The capacity for doing work possessed by electricityunder proper conditions. Electric energy may be either kinetic orpotential. As ordinary mechanical energy is a product of force andspace, so electric energy is a product of potential difference andquantity. Thus a given number of coulombs of electricity in falling agiven number of volts develop electric energy. The dimensions are foundtherefore 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 1E8absolute units of potential and the coulomb to 0.1 absolute units ofquantity, the volt-coulomb is equal to 1E7 absolute units of energy.The volt-coulomb is very seldom used, and the unit of Electric Activityor Power (see Power, Electric), the volt-ampere, is universally used.This unit is sometimes called the Watt, q. v., and it indicates the rateof expenditure or of production of electric energy.The storing up in a static accumulator or condenser of a given charge ofelectricity, available for use with a given change of potentialrepresents potential electric energy.The passing of a given quantity through a conductor with a given fall ofpotential represents kinetic electric energy.In a secondary battery there is no storage of energy, but the chargingcurrent simply accumulates potential chemical energy in the battery,which chemical energy is converted into electric energy in the dischargeor delivery of the battery.It is customary to discuss Ohm's law in this connection; it is properlytreated under Electric Power, to which the reader is referred. (SeePower, Electric.)[Transcriber's note: A volt-ampere or watt is a unit of power. Avolt-coulomb-second or watt-second is a unit of energy. Power multiplied bytime yields energy.]Energy, Electric Transmission of.If an electric current passes through a conductor all its energy isexpended in the full circuit. Part of the circuit may be an electricalgenerator that supplies energy as fast as expended. Part of the circuitmay be a motor which absorbs part of the energy, the rest being expendedin forcing a current through the connecting wires and through thegenerator. The electric energy in the generator and connecting wires isuselessly expended by conversion into heat. That in the motor in greatpart is utilized by conversion into mechanical energy which can douseful work. This represents the transmission of energy. Every electriccurrent system represents this operation, but the term is usuallyrestricted to the transmission of comparatively large quantities ofenergy.A typical installation might be represented thus. At a waterfall aturbine water wheel is established which drives a dynamo. From thedynamo wires are carried to a distant factory, where a motor or severalmotors are established, which receive current from the dynamo and drivethe machinery. The same current, if there is enough energy, may be usedfor running lamps or electroplating. As electric energy (see Energy,Electric,) is measured by the product of potential difference byquantity, a very small wire will suffice for the transmission of a smallcurrent at a high potential, giving a comparatively large quantity ofenergy. It is calculated that the energy of Niagara Falls could betransmitted through a circuit of iron telegraph wire a distance of over1,000 miles, but a potential difference of 135,000,000 volts would berequired, something quite impossible to obtain or manage.[Transcriber's note: Contemporary long distance power transmission linesuse 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 calledactual energy. The energy varies directly with the mass and with thesquare 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 asmolar energy. (See Energy, Molar.)Energy, Molar.The energy of masses of matter due to movements of or positions ofmatter in masses; such as the kinetic energy of a pound or of a ton inmotion, or the potential energy of a pound at an elevation of onehundred feet.Energy, Molecular.The potential energy due to the relations of molecules and set free bytheir change in the way of combination. It is potential for the samereason that applies to atomic and chemical energy, of which latter it isoften a form, although it is often physical energy. The potential energystored up in vaporization is physical and molecular energy; thepotential energy stored up in uncombined potassium oxide and water, orcalcium oxide (quicklime) and water is molecular, and when either twosubstances are brought together kinetic, thermal or heat energy is setfree, as in slaking lime for mortar.Energy of an Electrified Body.An electrified body implies the other two elements of a condenser. It isthe seat of energy set free when discharged. (See Dielectric, Energyof.) The two oppositely charged bodies tend to approach. This tendency,together with the distances separating them, represents a potentialenergy.Energy of Stress.Potential energy due to stress, as the stretching of a spring. This ishardly a form of potential energy. A stressed spring is merely in aposition to do work at the expense of its own thermal or kinetic energybecause it is cooled in doing work. If it possessed true potentialenergy of stress it would not be so cooled.Energy of Position.Potential energy due to position, as the potential energy of a poundweight raised ten feet (ten foot lbs.). (See Energy, Potential.)Energy, Physical.The potential energy stored up in physical position or set free inphysical change. Thus a vapor or gas absorbs energy in its vaporization,which is potential energy, and appears as heat energy when the vaporliquefies.242 STANDARD ELECTRICAL DICTIONARY.Energy, Potential, or Static Energy.The capacity for doing work in a system due to advantage of position orother cause, such as the stress of a spring. A pound weight supportedten feet above a plane has ten foot lbs. of potential energy of positionreferred to that plane. A given weight of an elementary substancerepresents potential chemical energy, which will be liberated as actualenergy in its combination with some other element for which it has anaffinity. Thus a ton of coal represents a quantity of potential chemicalenergy which appears in the kinetic form of thermal energy when the coalis burning in a furnace. A charged Leyden jar represents a source ofpotential electric energy, which becomes kinetic heat energy as the sameis discharged.Energy, Thermal.A form of kinetic molecular energy due to the molecular motion of bodiescaused by heat.Entropy.Non-available energy. As energy may in some way or other be generallyreduced to heat, it will be found that the equalizing of temperature,actual and potential, in a system, while it leaves the total energyunchanged, makes it all unavailable, because all work represents a fallin degree of energy or a fall in temperature. But in a system such asdescribed no such fall could occur, therefore no work could be done. Theuniverse is obviously tending in that direction. On the earth theexhaustion of coal is in the direction of degradation of its highpotential energy, so that the entropy of the universe tends to zero.(See Energy, Degradation of.)[Transcriber's note: Entropy (disorder) INCREASES, while AVAILABLEENERGY 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 thethermo-electric junction was heated or cooled. This is termed ElectricEntropy. (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 maybe suspended back of each brass plate as shown. The apparatus is chargedby connecting one plate to an electric machine and the other to theearth. The capacity of the plate connected to the machine is increasedby bringing near to it the grounded plate, by virtue of the principle ofbound charges. This apparatus is used to illustrate the principles ofthe electric condenser. It was invented after the Leyden jar wasinvented.Fig. 166. EPINUS' CONDENSER.E. P. S.Initials of Electrical Power Storage; applied to a type of secondarybattery 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 ofthe electro-magnet varying in intensity greatly over its range ofaction, into a pull of sensibly equal strength throughout. The use of arocking lever acting as a cam, with leverage varying as the armatureapproaches or recedes from the magnet core is one method of effectingthe result. Such is shown in the cut. E is an electro-magnet, witharmature a. A and B are the equalizer cams. The pull on the short end ofthe cam B is sensibly equal for its whole length.Many other methods have been devised, involving different shapes of polepieces, armatures or mechanical devices other than the one just shown.Equipotential. adj.Equal in potential; generally applied to surfaces. Thus every magneticfield is assumed to be made up of lines of force and intersecting thoselines, surfaces, plane, or more or less curved in contour, can bedetermined, over all parts of each one of which the magnetic intensitywill be identical. Each surface is the locus of equal intensity. Thesame type of surface can be constructed for any field of force, such asan electrostatic field, and is termed an equipotential surface.Equipotential Surface, Electrostatic.A surface in an electrostatic field of force, which is the locus of allpoints of a given potential in such field; a surface cutting all thelines of force at a point of identical potential. Lines of force are cutperpendicularly 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-magneticfield of force that an electrostatic equipotential surface (seeEquipotential Surface, Electrostatic,) does to an electrostatic field offorce.Equivalent, Chemical.The quotient obtained by dividing the atomic weight of an element by itsvalency.Equivalents, Electro-chemical.The weight of any substance set free by one coulomb of electricity. Thefollowing give some equivalents expressed in milligrams: