Chapter C: G. S (6)

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 animal system by an alternating or intermitting high potential discharge from an induction coil.

247 STANDARD ELECTRICAL DICTIONARY.

Excitability, Galvanic. The same as Faradic excitability, except that it refers to the effects of the current from a galvanic battery.

Excitability of Animal System, Electric. The susceptibility of a nerve or muscle to electric current shown by the effect produced by its application.

Exciter. A generator used for exciting the field magnet of a dynamo. In alternating current dynamos, e. g., of the Westinghouse type, a special dynamo is used simply to excite the field magnet. In central station distribution 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) of superficial expansion, (3) of cubic expansion or expansion of volume. The first and third are the only ones much used. They vary for different substances, and for the same substance at different temperatures. They are usually expressed as decimals indicating the mixed number referred to the length or volume of the body at the freezing point as unity.

Expansion, Electric. (a) The increase in volume of a condenser, when charged electrostatically. A Leyden jar expands when charged, and contracts when discharged.

(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 the wire in an electric fuse of the Abel type (see Fuse, Electric), and thereby determining an explosion.

(b) The term may also be applied to a small frictional or influence machine for producing a spark for exploding a spark fuse.

Explorer. A coil, similar to a magnetizing coil (see Coil, Magnetizing), used for investigating the electro-magnetic circuit and for similar purposes. If placed around an electro-magnet and connected with a galvanometer, it will produce a deflection, owing to a momentary induced current, upon any change in the magnet, such as removing or replacing the armature. It is useful in determining the leakage of lines of force and for general investigations of that nature. It is often called an exploring coil. Hughes' Induction Balance (see Induction Balance, Hughes') is sometimes called a Magnetic Explorer. The exploring coil may be put in circuit with a galvanometer for quantitative measurements or with a telephone for qualitative ones.

248 STANDARD ELECTRICAL DICTIONARY.

Extension Bell Call. A system of relay connection, q. v., by which a bell is made to continue ringing after the current has ceased coming over the main line. It is designed to prolong the alarm given by a magneto call bell, q. v., which latter only rings as long as the magneto handle is turned. A vibrating electric bell (see Bell, Electric,) is connected in circuit with a local battery and a switch normally open, but so constructed as to close the circuit when a current is passed and continue to do so indefinitely. The distant circuit is connected to this switch. When the magneto is worked it acts upon the switch, closes the local battery circuit and leaves it closed, while the bell goes on ringing until the battery is exhausted or the 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, bent into an almost complete circle 70 millimeters (.28 inch) in diameter, with terminals separated by an air gap. This is moved about in the region under examination, and by the production of a spark indicates the locality of the loops or venters in systems of stationary waves.

F. Abbreviation for Fahrenheit, as 10º F., meaning 10º Fahrenheit. (See Fahrenheit Scale.)

Fahrenheit Scale. A thermometer scale in use in the United States and England. On this scale the temperature of melting ice is 32°; that of condensing steam is 212°; the degrees are all of equal length. Its use is indicated by the letter F., as 180° F. To convert its readings into centigrade, subtract 32 and multiply by 5/9. (b) To convert centigrade into F. multiply by 9/5 and add 32. Thus 180° F. = ((180-32) * 5/9)° C. = 82.2° C. Again 180° C. = (180 * 9/5) + 32 = 324° F.

[Transcribers note: 180° C. = (180 * 9/5) + 32 = 356° F. ]

The additions and subtractions must be algebraic in all cases. Thus when the degrees are minus or below zero the rules for conversion might be put thus: To convert degrees F. below zero into centigrade to the number of degrees F. add 32, multiply by 5/9 and place a minus sign (-) before it. (b) To convert degrees centigrade below zero into Fahrenheit, multiply the number of degrees by 9/5, subtract from 32 if smaller; if greater than 32 subtract 32 therefrom, and prefix a minus sign, thus: -10° C. = 32 - (10 * 9/5) = 14°. Again, -30°C. = (30 * 9/5) - 32 = 22 = -22° F.

249 STANDARD ELECTRICAL DICTIONARY.

Farad. The practical unit of electric capacity; the capacity of a conductor which can retain one coulomb of electricity at a potential of one volt.

The quantity of electricity charged upon a conducting surface raises its potential; therefore a conductor of one farad capacity can hold two coulombs at two volts potential, and three coulombs at three volts, and so on. The electric capacity of a conductor, therefore, is relative compared to others as regards its charge, for the latter may be as great as compatible with absence of sparking and disruptive discharge. In other words, a one farad or two farad conductor may hold a great many coulombs. Charging a conductor with electricity is comparable to pumping air into a receiver. Such a vessel may hold one cubic foot of air at atmospheric pressure and two at two atmospheres, and yet be of one cubic foot capacity however much air is pumped into it.

The farad is equal to one fundamental electrostatic unit of capacity multiplied by 9E11 and to one electro-magnetic unit multiplied by 1E-9.

The farad although one of the practical units is far too large, so the micro-farad is used in its place. The capacity of a sphere the size of the earth is only .000636 of a farad.

[Transcriber's note: Contemporary calculations give about .000720 farad.]

Faraday, Effect. The effect of rotation of its plane produced upon a polarized beam of light by passage through a magnetic field. (See Magnetic Rotary Polarization.)

Faraday's Cube. To determine the surface action of a charge, Faraday constructed a room, twelve feet cube, insulated, and lined with tinfoil. This room he charged to a high potential, but within it he could detect no excitement whatever. The reason was because the electricity induced in the bodies within the room was exactly equal to the charge of the room-surface, and was bound exactly by it. The room is termed Faraday's cube.

Faraday's Dark Space. A non-luminous space between the negative and positive glows, produced in an incompletely exhausted tube through which a static discharge, as from an induction coil, is produced. It is perceptible in a rarefaction of 6 millimeters (.24 inch) and upwards. If the exhaustion is very high a dark space appears between the negative electrode and its discharge. This is known as Crookes' dark space.

Faraday's Disc. A disc of any metal, mounted so as to be susceptible of rotation in a magnetic field of force, with its axis parallel to the general direction of the lines of force. A spring bears against its periphery and another spring against its axle. When rotated, if the springs are connected by a conductor, a current is established through the circuit including the disc and conductor. The radius of the disc between the spring contacts represents a conductor cutting lines of force and generating a potential difference, producing a current. If a current is sent through the motionless wheel from centre to periphery it rotates, illustrating the doctrine of reversibility. As a motor it is called Barlow's or Sturgeon's Wheel. If the disc without connections is rapidly rotated it produces Foucault currents, q. v., within its mass, which resist its rotation and heat the disc.

250 STANDARD ELECTRICAL DICTIONARY.

Fig. 168. "FARADAY'S NET."

Faraday's Net. An apparatus for showing that the electric charge resides on the surface. It consists of a net, conical in shape and rather deep, to whose apex two threads, one on each side, are attached. Its mouth is fastened to a vertical ring and the whole is mounted on an insulating support.

It is pulled out to its full extent and is electrified. No charge can be detected inside it. By pulling one of the threads it is turned with the other side out. Now all the charge is found on the outside just as before, except that it is of course on the former inside surface of the bag. The interior shows no charge.

Faraday's Transformer. The first transformer. It was made by Michael Faraday. It was a ring of soft iron 7/8 inch thick, and 6 inches in external diameter. It was wound with bare wire, calico being used to prevent contact of the wire with the ring and of the layers of wire with each other, while twine was wound between the convolutions to prevent the wires from touching. Seventy-two feet of copper wire, 1/20 inch diameter, were wound in three superimposed coils, covering about one-half of the ring. On the other half sixty feet of copper wire were wound in two superimposed coils. Faraday connected his coils in different ways and used a galvanometer to measure the current produced by making and breaking one of the circuits used as a primary.

The coil is of historic interest.

Faraday's Voltameter. A voltameter, in which the coulombs of current are measured by the volume of the gas evolved from acidulated water. (See Voltameter, Gas.)

Faradic. adj. Referring to induced currents, produced from induction coils. As Faraday was the original investigator of the phenomena of electro-magnetic induction, the secondary or induced electro-magnetic currents and their phenomena and apparatus are often qualified by the adjective Faradic, especially in electro-therapeutics. A series of alternating electrostatic discharges, as from an influence machine (Holtz), are sometimes called Franklinic currents. They are virtually Faradic, except as regards their production.

251 STANDARD ELECTRICAL DICTIONARY.

Faradic Brush. A brush for application of electricity to the person. It is connected as one of the electrodes of an induction coil or magneto generator. For bristles wire of nickel plated copper is generally employed.

Faradization. In medical electricity the analogue of galvanization; the effects due to secondary or induced currents; galvanization referring to currents from a galvanic battery; also the process of application of such currents.

Faults. Sources of loss of current or of increased resistance or other troubles in electric circuits.

Feeder. A lead in an electric central station distribution system, which lead runs from the station to some point in the district to supply current. It is not used for any side connections, but runs direct to the point where current is required, thus "feeding" the district directly. In the two wire system a feeder may be positive or negative; in the three wire system there is also a neutral feeder. Often the term feeder includes the group of two or of three parallel lines.

Feeder Equalizer. An adjustable resistance connected in circuit with a feeder at the central station. The object of the feeder being to maintain a definite potential difference at its termination, the resistance has to be varied according to the current it is called on to carry.

Feeder, Main or Standard. The main feeder of a district. The standard regulation of pressure (potential difference between leads) in the district is often determined by the pressure at the end of the feeder.

Feeder, Negative. The lead or wire in a set of feeders, which is connected to the negative terminal of the generator.

Feeder, Neutral. In the three wire system the neutral wire in a set of feeders. It is often made of less diameter than the positive and negative leads.

Feeder, Positive. The lead or wire in a set of feeders, which wire is connected to the positive terminal of the generator.

Ferranti Effect. An effect as yet not definitely explained, observed in the mains of the Deptford, Eng., alternating current plant. It is observed that the potential difference between the members of a pair of mains rises or increases with the distance the place of trial is from the station.

[Transcriber's note: This effect is due to the voltage drop across the line inductance (due to charging current) being in phase with the sending end voltages. Both capacitance and inductance are responsible for producing this phenomenon. The effect is more pronounced in underground cables and with very light loads.]

252 STANDARD ELECTRICAL DICTIONARY.

Ferro-magnetic. adj. Paramagnetic; possessing the magnetic polarity of iron.

Fibre and Spring Suspension. A suspension of the galvanometer needle used in marine galvanometers. The needle is supported at its centre of gravity by a vertically stretched fibre attached at both its ends, but with a spring intercalated between the needle and one section of the fibre.

Fibre Suspension. Suspension, as of a galvanometer needle, by a vertical or hanging fibre of silk or cocoon fibre, or a quartz fibre. (See Quartz.)

This suspension, while the most delicate and reliable known, is very subject to disturbance and exacts accurate levelling of the instrument.

Fibre suspension is always characterized by a restitutive force. Pivot suspension, q. v., on the other hand, has no such force.

Field, Air. A field the lines of force of which pass through air; the position of a field comprised within a volume of air.

Field, Alternating. Polarity or direction being attributed to lines of force, if such polarity is rapidly reversed, an alternating field results. Such field may be of any kind, electro-magnetic or electrostatic. In one instance the latter is of interest. It is supposed to be produced by high frequency discharges of the secondary of an induction coil, existing in the vicinity of the discharging terminals.

Field Density. Field density or density of field is expressed in lines of force per unit area of cross-section perpendicular to the lines of force.

Field, Distortion of. The lines of force reaching from pole to pole of an excited field magnet of a dynamo are normally symmetrical with respect to some axis and often with respect to several. They go across from pole to pole, sometimes bent out of their course by the armature core, but still symmetrical. The presence of a mass of iron in the space between the pole pieces concentrates the lines of force, but does not destroy the symmetry of the field.

When the armature of the dynamo is rotated the field becomes distorted, and the lines of force are bent out of their natural shape. The new directions of the lines of force are a resultant of the lines of force of the armature proper and of the field magnet. For when the dynamo is started the armature itself becomes a magnet, and plays its part in forming the field. Owing to the lead of the brushes the polarity of the armature is not symmetrical with that of the field magnets. Hence the compound field shows distortion. In the cut is shown diagrammatically the distortion of field in a dynamo with a ring armature. The arrow denotes the direction of rotation, and n n * * * and s s * * * indicate points of north and south polarity respectively.

253 STANDARD ELECTRICAL DICTIONARY.

The distorted lines must be regarded as resultants of the two induced polarities of the armature, one polarity due to the induction of the field, the other to the induction from its own windings. The positions of the brushes have much to do with determining the amount and degree of distortion. In the case of the ring armature it will be seen that some of the lines of force within the armature persist in their polarity and direction, almost as induced by the armature windings alone, and leak across without contributing their quota to the field. Two such lines are shown in dotted lines.

In motors there is a similar but a reversed distortion.

Fig. 169. DISTORTION OF FIELD IN A RING ARMATURE OF AN ACTIVE DYNAMO.

Fig. 170. DISTORTION OF FIELD IN A RING ARMATURE OF AN ACTIVE MOTOR.

254 STANDARD ELECTRICAL DICTIONARY.

Field, Drag of. When a conductor is moved through a field so that a current is generated in it, the field due to that current blends with the other field and with its lines of force, distorting the field, thereby producing a drag upon its own motion, because lines of force always tend to straighten themselves, and the straightening would represent cessation of motion in the conductor. This tendency to straightening therefore resists the motion of the conductor and acts a drag upon it.

Field of Force. The space in the neighborhood of an attracting or repelling mass or system. Of electric fields of force there are two kinds, the Electrostatic and the Magnetic Fields of Force, both of which may be referred to. A field of force may be laid out as a collection of elements termed Lines of Force, and this nomenclature is universally adopted in electricity. The system of lines may be so constructed that (a) the work done in passing from one equipotential surface to the next is always the same; or (b) the lines of force are so laid out and distributed that at a place in which unit force is exercised there is a single line of force passing through the corresponding equipotential surface in each unit of area of that surface. The latter is the universal method in describing electric fields. It secures the following advantages:--First: The potential at any point in the field of space surrounding the attracting or repelling mass or masses is found by determining on which imaginary equipotential surface that point lies. Second: If unit length of a line of force cross n equipotential surfaces, the mean force along that line along the course of that part of it is equal to n units; for the difference of potential of the two ends of that part of the line of force = n; it is also equal to F s (F = force), because it represents numerically a certain amount of work; but s = I, whence n = F. Third: The force at any part of the field corresponds to the extent to which the lines of force are crowded together; and thence it may be determined by the number of lines of force which pass through a unit of area of the corresponding equipotential surface, that area being so chosen as to comprise the point in question. (Daniell.)

Field of Force, Electrostatic. The field established by the attracting, repelling and stressing influence of an electrostatically charged body. It is often termed an Electrostatic Field. (See Field of Force.)

255 STANDARD ELECTRICAL DICTIONARY.

Field of Force of a Current. A current establishes a field of force around itself, whose lines of force form circles with their centres on the axis of the current. The cut, Fig. 172, shows the relation of lines of force to current.

Fig. 171. EXPERIMENT SHOWING LINES OF FORCE SURROUNDING AN ACTIVE CONDUCTOR.

Fig. 172. DIAGRAM OF FIELD OF FORCE SURROUNDING AN ACTIVE CONDUCTOR.

Fig. 173. LINK OF FORCE INDUCED BY A CURRENT SHOWING THE MAGNETIC WHIRLS.

The existence of the field is easily shown by passing a conductor vertically through a horizontal card. On causing a current to go through the wire the field is formed, and iron filings dropped upon the card, tend, when the latter is gently tapped, to take the form of circles. The experiment gives a version of the well-known magnetic figures, q. v. See Fig. 171.

The cut shows by the arrows the relation of directions of current to the direction of the lines of force, both being assumptions, and merely indicating certain fixed relations, corresponding exactly to the relations expressed by the directions of electro-magnetic or magnetic lines of force

256 STANDARD ELECTRICAL DICTIONARY.

Field, Pulsatory. A field produced by pulsatory currents. By induction such field can produce an alternating current.

Field, Rotating. In a dynamo the field magnets are sometimes rotated instead of the armature, the latter being stationary. In Mordey's alternator the armature, nearly cylindrical, surrounds the field, and the latter rotates within it, the arrangement being nearly the exact reverse of the ordinary one. This produces a rotating field.

Field, Rotatory. A magnetic field whose virtual poles keep rotating around its centre of figure. If two alternating currents differing one quarter period in phase are carried around four magnetizing coils placed and connected in sets of two on the same diameter and at right angles to each other, the polarity of the system will be a resultant of the combination of their polarity, and the resultant poles will travel round and round in a circle. In such a field, owing to eddy currents, masses of metal, journaled like an armature, will rotate, with the speed of rotation of the field.

Field, Stray. The portion of a field of force outside of the regular circuit; especially applied to the magnetic field of force of dynamos expressing the portion which contributes nothing to the current generation.

Synonym--Waste Field.

Field, Uniform. A field of force of uniform density. (See Field Density.)

Figure of Merit. In the case of a galvanometer, a coefficient expressing its delicacy. It is the reciprocal of the current required to deflect the needle through one degree. By using the reciprocal the smaller the current required the larger is the figure of merit. The same term may be applied to other instruments.

It is often defined as the resistance of a circuit through which one Daniell's element will produce a deflection of one degree on the scale of the instrument. The circuit includes a Daniell's cell of resistance r, a rheostat R, galvanometer G and shunt S. Assume that with the shunt in parallel a deflection of a divisions is obtained. The resistance of the shunted galvanometer is (GS/G+S ; the multiplying power m of the shunt is S+G/S; the formula or figure of merit is m d (r+R +G S/G+S).

The figure of merit is larger as the instrument is more sensitive. Synonym--Formula of Merit.

257 STANDARD ELECTRICAL DICTIONARY.

Filament. A thin long piece of a solid substance. In general it is so thin as to act almost like a thread, to be capable of standing considerable flexure. The distinction between filament and rod has been of much importance in some patent cases concerning incandescent lamps. As used by electricians the term generally applies to the carbon filament of incandescent lamps. This as now made has not necessarily any fibres, but is entitled to the name of filament, partly by convention, partly by its relative thinness and want of stiffness. (See Incandescent Lamps--Magnetic Filament.)

Fire Alarm, Electric, Automatic. A system of telegraph circuits, at intervals supplied with thermostats or other apparatus affected by a change of temperature, which on being heated closes the circuit and causes a bell to ring. (See Thermostat.)

Fire Alarm Telegraph System. A system of telegraphic lines for communicating the approximate location of a fire to a central station and thence to the separate fire-engine houses in a city or district. It includes alarm boxes, distributed at frequent intervals, locked, with the place where the key is kept designated, or in some systems left unlocked. On opening the door of the box and pulling the handle or otherwise operating the alarm, a designated signal is sent to the central station. From this it is telegraphed by apparatus worked by the central station operator to the engine houses. The engines respond according to the discipline of the service.

Fire Cleansing. Freeing the surface of an article to be plated from grease by heating.

Fire Extinguisher, Electric, Automatic. A modification of the electric fire alarm (see Fire Alarm, Electric, Automatic), in which the thermostats completing the circuits turn on water which, escaping through the building, is supposed to reach and extinguish a fire.

Flashing in a Dynamo or Magneto-electric Generator. Bad adjustment of the brushes at the commutator, or other fault of construction causes the production of voltaic arcs at the commutator of a generator, to which the term flashing is applied.

Flashing of Incandescent Lamp Carbons. A process of treatment for the filaments of incandescent lamps. The chamber before sealing up is filled with a hydro-carbon vapor or gas, such as the vapor of a very light naphtha (rhigolene). A current is then passed through the filament heating it to redness. The more attenuated parts or those of highest resistance are heated the highest, and decompose most rapidly the hydro-carbon vapor, graphitic carbon being deposited upon these parts, while hydrogen is set free. This goes on until the filament is of uniform resistance throughout. It gives also a way of making the resistance of the filament equal to any desired number of ohms, provided it is originally of high enough resistance. The process increases the conductivity of the filament.

After flashing the chambers are pumped out and sealed up.

258 STANDARD ELECTRICAL DICTIONARY.

Flashing Over. A phenomenon observed in high potential dynamos. On a sudden alteration of the resistance of the circuit a long blue spark will be drawn out around the surface of the commutator from brush to brush. The spark is somewhat of the nature of an arc, and may seriously injure commutators whose sections are only separated by mica, or other thin insulation. In the case of commutators whose sections are separated by air spaces it is not so injurious.

Flats. In a commutator of a dynamo, the burning or wearing away of a commutator segment to a lower level than the rest. Sometimes two adjacent bars will be thus affected, causing a flat place on the commutator. It is not always easy to account for the formation of flats. They may have their origin in periodic vibrations due to bad mounting, or to sparking at the particular point.

Floor Push. A press or push button constructed to be set into the floor to be operated by pressing with the foot. It is used to ring an alarm bell, sound a buzzer or for similar service.

Fluid, Depolarizing. A fluid used in voltaic batteries to dispose of the hydrogen, which goes to the negative plate. This it does by oxidizing it. Chromic acid, nitric acid, and chloric acids are among the constituents of liquid depolarizers. (See Electropoion Fluid.)

Fluid, Electric. The electric current and charge have sometimes been attributed to a fluid. The theory, which never was much more than hypothetical, survives to some extent in the single and double fluid theory. (See Single Fluid Theory-Double Fluid Theory.)

Fluorescence. The property of converting ether waves of one length, sometimes of invisible length, into waves of another length (visible). AEsculin, quinine salts, uranium glass and other substances exhibit this phenomenon. The phenomenon is utilized in the production of Geissler tubes.

Flush Boxes. A heavy iron box covered with a heavy hand plate and laid flush (whence the name), or even with the surface of a roadway. Into it conductors of an underground system lead, and it is used to make connections therewith and for examining the leakage of the conductors and for similar purposes. It is a "man-hole" (q. v.) in miniature.

Fluviograph. An electric registering tide gauge or water level gauge.

259 STANDARD ELECTRICAL DICTIONARY.

Fly or Flyer, Electric. A little wheel, ordinarily poised on a point, like a compass needle. It carries several tangentially directed points, all pointing in the same sense. When connected with a source of electricity of high potential it revolves by reaction. The tension of its charge is highest at the points, the air there is highly electrified and repelled, the reaction pushing the wheel around like a Barker's mill or Hero's steam engine. Sometimes the flyer is mounted with its axis horizontal and across the rails on a railroad along which it travels.

Synonym--Reaction Wheel.

Foci Magnetic. The two points on the earth's surface where the magnetic intensity is greatest. They nearly coincide in position with the magnetic poles.

Fog, Electric. Fogs occurring when the atmosphere is at unusually high potential and accompanied by frequent change of such polarity.

Following Horns. In dynamo-electric machines the projecting ends of the pole pieces towards which the outer uncovered perimeter of the armature turns in its regular operations. The leading horns are those away from which the armature rotates. In considering rotation the exposed portion of the superficies of the armature is considered. The definition would have to be reversed if the part facing the pole pieces were considered.

Synonym--Trailing Horns.

Foot-candle. A unit of illuminating power; the light given by one standard candle at a distance of one foot. The ordinary units of illuminating power are entirely relative; this is definite. It is due to Carl Herring.

Foot-pound. A practical unit of work or energy. The quantity of work required to raise a pound one foot, or one hundred pounds one-hundredth of a foot, and so on; or the potential energy represented by a weight at an elevation under these conditions.

Foot-step. In a dynamo with armature at the lower end of its field magnets, the plate generally of zinc, interposed between it and the iron base plate to prevent the leakage of lines of force outside of the circuit. Any diamagnetic material which is mechanically suitable may be used.

Force. Force may be variously defined. (a) Any cause of change of the condition of matter with respect to motion or rest.

(b) A measurable action upon a body under which the state of rest of that body, or its state of uniform motion in a straight line, suffers change.

(c) It may be defined by its measurement as the rate of change of momentum, or

(d) as the rate at which work is done per unit of space traversed.

Force is measured by the acceleration or change of motion it can impart to a body of unit mass in a unit of time, or, calling force, F, mass, m acceleration per second a we have F = m a.

The dimensions of force are mass (M) * acceleration (L/(T^2)) = (M*L)/(T^2).

260 STANDARD ELECTRICAL DICTIONARY.

Force de Cheval. Horse power (French).
It is the French or metric horse power.
It is equal to:
542.496 Foot lbs. per second.
.9864 English Horse Power.
75.0 Kilogram-meters per second.

Force, Electro-magnetic. The mechanical force of attraction or repulsion acting on the electro-magnetic unit of quantity. Its intensity varies with the square of the distance. It may also be defined as electric force in the electro-magnetic system.

Its dimensions are equal to mechanical force ((M*L)/(T^2)) divided by quantity ((M^.5)*(L^.5)) = ((M^.5)*(L^.5))/(T^2).

Force, Electrostatic. The force by which electric matter or electrified surfaces attract or repel each other. It is also termed electric force (not good) and electro-motive intensity. It is the mechanical force acting upon a unit quantity of electricity. Its intensity varies with the square of the distance.

Its dimensions are therefore equal to (quantity * unity / (square of distance) Q. * 1 / (L^2) = ((M^.5) * (L^1.5) )/ T*1 / (L^2) = ((M^.5) * (L^.5)) / T These dimensions are also those of potential difference.

[Transcriber's Note: The image of the preceding paragraph is included for "clarity".]

The objection to the term electric force is that it may be applied also to electro-magnetic force, and hence be a source of confusion.

Forces, Parallelogram of. The usual method of composing forces or resolving a force. The sides of a parallelogram of forces represent component forces and the diagonal represents the resultant. See Component--Resultant--Forces, Composition of--Forces, Resolution of.

Forces, Composition of. When several forces act in a different direction upon a point they may be drawn or graphically represented as arrows or lines emanating from the point in the proper direction and of lengths proportional to the force they exercise. Any two can be treated as contiguous sides of a parallelogram and the parallelogram can be completed. Then its diagonal, called the resultant, will represent the combined action of the two forces, both as regards direction and intensity. This is the composition of two forces.

If more than two forces act upon the given point the resultant can be composed with any of the others and a new force developed. The new resultant can be combined with another force, and the process kept up, eliminating the components one by one until a final resultant of all is obtained. This will give the exact direction and intensity of the forces, however many or varied.

261 STANDARD ELECTRICAL DICTIONARY.

Forces, Resolution of. The developing from a single force treated as a resultant, two other forces in any desired direction. The reverse of composition of forces. (See Forces, Composition of--Forces, Parallelogram of--Components--Resultant.)

Force, Tubes of. Aggregations of lines of force, either electrostatic or magnetic. They generally have a truncated, conical or pyramidal shape and are not hollow. Every cross-section contains the same number of lines. The name it will seem is not very expressive.

Force, Unit of. The fundamental or C. G. S. unit or force is the dyne, q. v.

The British unit of force is the poundal (the force which will produce an acceleration of one foot per second in a mass of one pound). It is equal to about 10/322 pound. A force cannot be expressed accurately in weight units, because weight varies with the latitude.

Forming. The process of producing secondary battery plates from lead plates by alternately passing a charging current through the cell and then allowing it to discharge itself and repeating the operation. (See Battery, Secondary, Planté's.)

Foundation Ring. In a dynamo armature the ring-shaped core on which Gramme ring armatures and other ring armatures are wound.

Fourth State of Matter. Gas so rarefied that its molecules do not collide, or rarely do so; radiant matter, q. v.

[Transcriber's note: This term now refers to plasma, an ionized gas, which contains free electrons. The ions and electrons move somewhat independently making plasma electrically conductive. It responds strongly to electromagnetic fields.]

Frame. In a dynamo the bed-piece is sometimes called the frame.

Franklin's Experiment. Franklin proved the identity of lightning and electricity by flying a kite in a thunder storm. The kite was of silk so as to endure the wetting. When the string became wet sparks could be taken from a key attached to its end. The main string was of hemp; at the lower end was a length of silk to insulate it. The key was attached near the end of and to the hemp string.

Franklin's Plate. A simple form of condenser. It consists of a plate of glass coated on each side with tinfoil with a margin of about an inch of clear glass. One coating may be grounded as indicated in the cut, and the plate charged like a Leyden jar. Or one side may be connected with one terminal, and the other with the other terminal of an influence machine and the pane will be thus charged.

Synonym--Fulminating Pane.

262 STANDARD ELECTRICAL DICTIONARY.

Fig. 174. FRANKLIN'S PLATE.

Franklin's Theory. The single fluid theory, q. v., of electricity.

Frequency. The number of double reversals or complete alternations per second in an alternating current.

Synonym--Periodicity.

Frictional Electricity. Electricity produced by friction of dissimilar substances. (See Electrostatic Series.) The contact theory holds that friction plays only a secondary rôle in this process; that it increases the thoroughness of contact, and tends to dry the rubbing surfaces, but that the charges induced are due to contact of dissimilar substances, not to friction of one against the other.

Frictional Heating. The heating of a conductor by the passage of a current; the Joule effect, q. v.

Fringe. The outlying edge of a magnetic field.

Frog, Galvani's Experiment With. A classic experiment in electricity, leading to the discovery of current or dynamic electricity. If a pair of legs of a recently killed frog are prepared with the lumbar nerves exposed near the base of the spinal column, and if a metallic conductor, one half-length zinc and the other half-length copper, is held, one end between the lumbar nerves and the spine, and the other end against one of the muscles of the thigh or lower legs, the moment contact occurs and the circuit is completed through the animal substance the muscles contract and the leg is violently drawn upwards. Galvani, in 1786, first performed, by accident, this famous experiment, it is said, with a scalpel with which he was dissecting the animal. He gave his attention to the nerves and muscles. Volta, more happily, gave his attention to the metals and invented the voltaic battery, described by him in a letter to Sir Joseph Banks, dated 1800.

Frog, Rheoscopic. If the nerve or living muscle of a frog is suddenly dropped upon another living muscle so as to come in contact with its longitudinal and transverse sections, the first muscle will contract on account of the stimulation of its nerve due to the passage of a current derived from the second muscle (Ganot). The experiment goes under the above title.

263 STANDARD ELECTRICAL DICTIONARY.

Frying. A term applied to a noise sometimes produced in a voltaic arc due to too close approach of the carbons to each other. It has been suggested that it may be due to volatilization of the carbon. (Elihu Thomson.)

Fulgurite. An irregular and tubular mass of vitrified quartz, believed to be formed by melting under the lightning stroke.

Fig. 175. CRUCIBLE, ELECTRIC.

Furnace, Electric. A furnace in which the heat is produced by the electric current. It has hitherto been practically used only in the extraction of aluminum and silicium from their ores. The general principle involves the formation of an arc between carbon electrodes. The substances to be treated are exposed to the heat thus produced. Sometimes the substances in the arc form imperfect conductors, and incandescence takes a part in the action. Sometimes the substances are merely dropped through the arc.

[Transcriber's note: Silicium is silicon.]

Fuse Board. A tablet on which a number of safety fuses are mounted. Slate is excellent material for the tablet, as it is incombustible, and is easily drilled and worked.

Fuse Box. A box containing a safety fuse. Porcelain is an excellent material for its base. No combustible material should enter into its composition.

Fuse, Cockburn. A safety fuse or cut off which consists of a wire of pure tin running from terminal to terminal, to whose centre a leaden ball is secured by being cast into position. The connection with the terminals is made by rings at the ends of the wire through which the terminal screws are passed and screwed home. When the tin softens under too heavy a current the weight of the shot pulls it apart.

Fig. 176 COCKBURN SAFETY FUSE.

264 STANDARD ELECTRICAL DICTIONARY.

Fig. 177. ELECTRIC FUSE.

Fuse, Electric. A fuse for igniting an explosive by electricity. There are two kinds. In one a thin wire unites the ends of the two conducting wires as they enter the case of the fuse. The larger wires are secured to the case, so that no strain comes on the fine wire. On passing a current of sufficient strength the small wire is heated. In use the fuse is bedded in powder, which again may be surrounded by fulminating powder, all contained in a copper or other metallic case. Such a detonator is used for exploding guncotton and other high explosives.

The other kind of fuse is similar, but has no thin connecting wire. The ends of the conductors are brought nearer together without touching. In use a static discharge is produced across from end to end of the conductors, igniting a proper explosive placed there as in the other case.

The first kind of fuse is generally operated by a battery or small mechanical generator--the latter by a spark coil, frictional or influence machine or by a Leyden jar.

Galvanic. adj. Voltaic; relating to current electricity or the electrolytic and electro-chemical relations of metals. (For titles in general under this head see Voltaic--or the main title.)

Galvanic Element. A galvanic couple with exciting fluid and adjuncts; a galvanic cell. The word element is sometimes applied to the electrodes of a cell, as the carbon element or zinc element.

265 STANDARD ELECTRICAL DICTIONARY.

Galvanic Polarization. The polarization of a voltaic couple. (See Polarization.)

Galvanism. The science of voltaic or current electricity.

Galvanization. (a) Electroplating or depositing a metal over the surface of another by electrolysis.

(b) In medical electricity the effects produced on any part of the system by the current of voltaic battery. Various descriptive qualifications are prefixed, such as "general" galvanization, indicating its application as applied to the whole body, "local" for the reverse case, and so on.

Galvanization, Labile. Application of the galvanic current in electro-therapeutics where one sponge electrode is employed which is rubbed or moved over the body, the other being in constant contact with the body.

Galvanized Iron. Iron coated with zinc by cleaning and immersion in melted zinc. The iron is prevented from rusting by galvanic action. It forms the negative element in a couple of which the zinc is the positive element. From this electric protective action the name is derived.

Galvano-cautery, Chemical. Electro-therapeutic treatment with sharp electrodes, one of which is inserted in the tissue and a current passed by completing the circuit through the tissue so as to electrolyze or decompose the fluids of the tissue. It is applied in the removal of hair or extirpation of the follicle. The process is not one of heating, and is improperly named cautery.

Galvano-faradization. In medical electricity the application of the voltaic and induced or secondary current simultaneously to any part of the system.

Galvanometer. An instrument for measuring current strength and sometimes for measuring inferentially potential difference, depending on the action of a magnetic field established by the current, such action being exerted on a magnetic needle or its equivalent.