248 STANDARD ELECTRICAL DICTIONARY.F.Abbreviation for Fahrenheit, as 10º F., meaning 10º Fahrenheit. (SeeFahrenheit Scale.)Fahrenheit Scale.A thermometer scale in use in the United States and England. On thisscale the temperature of melting ice is 32°; that of condensing steam is212°; the degrees are all of equal length. Its use is indicated by theletter F., as 180° F. To convert its readings into centigrade, subtract32 and multiply by 5/9. (b) To convert centigrade into F. multiply by9/5 and add 32. Thus 180° F. = ((180-32) * 5/9)° C. = 82.2° C. Again180° 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 whenthe degrees are minus or below zero the rules for conversion might beput thus: To convert degrees F. below zero into centigrade to the numberof degrees F. add 32, multiply by 5/9 and place a minus sign (-) beforeit. (b) To convert degrees centigrade below zero into Fahrenheit,multiply the number of degrees by 9/5, subtract from 32 if smaller; ifgreater 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 conductorwhich can retain one coulomb of electricity at a potential of one volt.The quantity of electricity charged upon a conducting surface raises itspotential; therefore a conductor of one farad capacity can hold twocoulombs at two volts potential, and three coulombs at three volts, andso on. The electric capacity of a conductor, therefore, is relativecompared to others as regards its charge, for the latter may be as greatas compatible with absence of sparking and disruptive discharge. Inother words, a one farad or two farad conductor may hold a great manycoulombs. Charging a conductor with electricity is comparable to pumpingair into a receiver. Such a vessel may hold one cubic foot of air atatmospheric pressure and two at two atmospheres, and yet be of one cubicfoot capacity however much air is pumped into it.The farad is equal to one fundamental electrostatic unit of capacitymultiplied 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 themicro-farad is used in its place. The capacity of a sphere the size ofthe earth is only .000636 of a farad.[Transcriber's note: Contemporary calculations give about .000720farad.]Faraday, Effect.The effect of rotation of its plane produced upon a polarized beam oflight by passage through a magnetic field. (See Magnetic RotaryPolarization.)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 hecharged to a high potential, but within it he could detect no excitementwhatever. The reason was because the electricity induced in the bodieswithin the room was exactly equal to the charge of the room-surface, andwas 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, producedin an incompletely exhausted tube through which a static discharge, asfrom an induction coil, is produced. It is perceptible in a rarefactionof 6 millimeters (.24 inch) and upwards. If the exhaustion is very higha 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 amagnetic field of force, with its axis parallel to the general directionof the lines of force. A spring bears against its periphery and anotherspring against its axle. When rotated, if the springs are connected by aconductor, a current is established through the circuit including thedisc and conductor. The radius of the disc between the spring contactsrepresents a conductor cutting lines of force and generating a potentialdifference, producing a current. If a current is sent through themotionless wheel from centre to periphery it rotates, illustrating thedoctrine of reversibility. As a motor it is called Barlow's orSturgeon's Wheel. If the disc without connections is rapidly rotated itproduces Foucault currents, q. v., within its mass, which resist itsrotation 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 thesurface. It consists of a net, conical in shape and rather deep, towhose apex two threads, one on each side, are attached. Its mouth isfastened to a vertical ring and the whole is mounted on an insulatingsupport.It is pulled out to its full extent and is electrified. No charge can bedetected inside it. By pulling one of the threads it is turned with theother side out. Now all the charge is found on the outside just asbefore, except that it is of course on the former inside surface of thebag. The interior shows no charge.Faraday's Transformer.The first transformer. It was made by Michael Faraday. It was a ring ofsoft iron 7/8 inch thick, and 6 inches in external diameter. It waswound with bare wire, calico being used to prevent contact of the wirewith the ring and of the layers of wire with each other, while twine waswound between the convolutions to prevent the wires from touching.Seventy-two feet of copper wire, 1/20 inch diameter, were wound in threesuperimposed coils, covering about one-half of the ring. On the otherhalf sixty feet of copper wire were wound in two superimposed coils.Faraday connected his coils in different ways and used a galvanometer tomeasure the current produced by making and breaking one of the circuitsused as a primary.The coil is of historic interest.Faraday's Voltameter.A voltameter, in which the coulombs of current are measured by thevolume of the gas evolved from acidulated water. (See Voltameter, Gas.)Faradic. adj.Referring to induced currents, produced from induction coils. As Faradaywas the original investigator of the phenomena of electro-magneticinduction, the secondary or induced electro-magnetic currents and theirphenomena and apparatus are often qualified by the adjective Faradic,especially in electro-therapeutics. A series of alternatingelectrostatic discharges, as from an influence machine (Holtz), aresometimes called Franklinic currents. They are virtually Faradic, exceptas regards their production.251 STANDARD ELECTRICAL DICTIONARY.Faradic Brush.A brush for application of electricity to the person. It is connected asone of the electrodes of an induction coil or magneto generator. Forbristles wire of nickel plated copper is generally employed.Faradization.In medical electricity the analogue of galvanization; the effects due tosecondary or induced currents; galvanization referring to currents froma galvanic battery; also the process of application of such currents.Faults.Sources of loss of current or of increased resistance or other troublesin electric circuits.Feeder.A lead in an electric central station distribution system, which leadruns 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 pointwhere current is required, thus "feeding" the district directly. In thetwo wire system a feeder may be positive or negative; in the three wiresystem there is also a neutral feeder. Often the term feeder includesthe group of two or of three parallel lines.Feeder Equalizer.An adjustable resistance connected in circuit with a feeder at thecentral station. The object of the feeder being to maintain a definitepotential difference at its termination, the resistance has to be variedaccording 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 determinedby the pressure at the end of the feeder.Feeder, Negative.The lead or wire in a set of feeders, which is connected to the negativeterminal of the generator.Feeder, Neutral.In the three wire system the neutral wire in a set of feeders. It isoften 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 thepositive terminal of the generator.Ferranti Effect.An effect as yet not definitely explained, observed in the mains of theDeptford, Eng., alternating current plant. It is observed that thepotential difference between the members of a pair of mains rises orincreases with the distance the place of trial is from the station.[Transcriber's note: This effect is due to the voltage drop across theline inductance (due to charging current) being in phase with thesending end voltages. Both capacitance and inductance are responsiblefor producing this phenomenon. The effect is more pronounced inunderground 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 verticallystretched fibre attached at both its ends, but with a springintercalated between the needle and one section of the fibre.Fibre Suspension.Suspension, as of a galvanometer needle, by a vertical or hanging fibreof silk or cocoon fibre, or a quartz fibre. (See Quartz.)This suspension, while the most delicate and reliable known, is verysubject to disturbance and exacts accurate levelling of the instrument.Fibre suspension is always characterized by a restitutive force. Pivotsuspension, 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 afield comprised within a volume of air.Field, Alternating.Polarity or direction being attributed to lines of force, if suchpolarity is rapidly reversed, an alternating field results. Such fieldmay be of any kind, electro-magnetic or electrostatic. In one instancethe latter is of interest. It is supposed to be produced by highfrequency discharges of the secondary of an induction coil, existing inthe vicinity of the discharging terminals.Field Density.Field density or density of field is expressed in lines of force perunit 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 magnetof a dynamo are normally symmetrical with respect to some axis and oftenwith respect to several. They go across from pole to pole, sometimesbent out of their course by the armature core, but still symmetrical.The presence of a mass of iron in the space between the pole piecesconcentrates the lines of force, but does not destroy the symmetry ofthe 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 newdirections of the lines of force are a resultant of the lines of forceof the armature proper and of the field magnet. For when the dynamo isstarted the armature itself becomes a magnet, and plays its part informing the field. Owing to the lead of the brushes the polarity of thearmature is not symmetrical with that of the field magnets. Hence thecompound field shows distortion. In the cut is shown diagrammaticallythe distortion of field in a dynamo with a ring armature. The arrowdenotes the direction of rotation, and n n * * * and s s * * * indicatepoints of north and south polarity respectively.253 STANDARD ELECTRICAL DICTIONARY.The distorted lines must be regarded as resultants of the two inducedpolarities of the armature, one polarity due to the induction of thefield, the other to the induction from its own windings. The positionsof the brushes have much to do with determining the amount and degree ofdistortion. In the case of the ring armature it will be seen that someof the lines of force within the armature persist in their polarity anddirection, almost as induced by the armature windings alone, and leakacross without contributing their quota to the field. Two such lines areshown in dotted lines.In motors there is a similar but a reversed distortion.Fig. 169. DISTORTION OF FIELD IN ARING ARMATURE OF AN ACTIVE DYNAMO.Fig. 170. DISTORTION OF FIELD IN ARING 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 generatedin it, the field due to that current blends with the other field andwith its lines of force, distorting the field, thereby producing a dragupon its own motion, because lines of force always tend to straightenthemselves, and the straightening would represent cessation of motion inthe conductor. This tendency to straightening therefore resists themotion of the conductor and acts a drag upon it.Field of Force.The space in the neighborhood of an attracting or repelling mass orsystem. Of electric fields of force there are two kinds, theElectrostatic and the Magnetic Fields of Force, both of which may bereferred to. A field of force may be laid out as a collection ofelements termed Lines of Force, and this nomenclature is universallyadopted in electricity. The system of lines may be so constructed that(a) the work done in passing from one equipotential surface to the nextis always the same; or (b) the lines of force are so laid out anddistributed that at a place in which unit force is exercised there is asingle line of force passing through the corresponding equipotentialsurface in each unit of area of that surface. The latter is theuniversal method in describing electric fields. It secures the followingadvantages:--First: The potential at any point in the field of spacesurrounding the attracting or repelling mass or masses is found bydetermining on which imaginary equipotential surface that point lies.Second: If unit length of a line of force cross n equipotentialsurfaces, the mean force along that line along the course of that partof it is equal to n units; for the difference of potential of the twoends 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 fieldcorresponds to the extent to which the lines of force are crowdedtogether; and thence it may be determined by the number of lines offorce which pass through a unit of area of the correspondingequipotential surface, that area being so chosen as to comprise thepoint in question. (Daniell.)Field of Force, Electrostatic.The field established by the attracting, repelling and stressinginfluence of an electrostatically charged body. It is often termed anElectrostatic 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 offorce form circles with their centres on the axis of the current. Thecut, Fig. 172, shows the relation of lines of force to current.Fig. 171. EXPERIMENT SHOWING LINES OF FORCESURROUNDING AN ACTIVE CONDUCTOR.Fig. 172. DIAGRAM OF FIELD OF FORCESURROUNDING AN ACTIVE CONDUCTOR.Fig. 173. LINK OF FORCE INDUCED BY ACURRENT SHOWING THE MAGNETIC WHIRLS.The existence of the field is easily shown by passing a conductorvertically through a horizontal card. On causing a current to go throughthe 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. Theexperiment gives a version of the well-known magnetic figures, q. v. SeeFig. 171.The cut shows by the arrows the relation of directions of current to thedirection of the lines of force, both being assumptions, and merelyindicating certain fixed relations, corresponding exactly to therelations expressed by the directions of electro-magnetic or magneticlines of force256 STANDARD ELECTRICAL DICTIONARY.Field, Pulsatory.A field produced by pulsatory currents. By induction such field canproduce an alternating current.Field, Rotating.In a dynamo the field magnets are sometimes rotated instead of thearmature, the latter being stationary. In Mordey's alternator thearmature, nearly cylindrical, surrounds the field, and the latterrotates within it, the arrangement being nearly the exact reverse of theordinary one. This produces a rotating field.Field, Rotatory.A magnetic field whose virtual poles keep rotating around its centre offigure. If two alternating currents differing one quarter period inphase are carried around four magnetizing coils placed and connected insets of two on the same diameter and at right angles to each other, thepolarity of the system will be a resultant of the combination of theirpolarity, and the resultant poles will travel round and round in acircle. In such a field, owing to eddy currents, masses of metal,journaled like an armature, will rotate, with the speed of rotation ofthe 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 expressingthe 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. Itis the reciprocal of the current required to deflect the needle throughone degree. By using the reciprocal the smaller the current required thelarger is the figure of merit. The same term may be applied to otherinstruments.It is often defined as the resistance of a circuit through which oneDaniell's element will produce a deflection of one degree on the scaleof the instrument. The circuit includes a Daniell's cell of resistancer, a rheostat R, galvanometer G and shunt S. Assume that with the shuntin parallel a deflection of a divisions is obtained. The resistance ofthe shunted galvanometer is (GS/G+S ; the multiplying power m of theshunt 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 toact almost like a thread, to be capable of standing considerableflexure. The distinction between filament and rod has been of muchimportance in some patent cases concerning incandescent lamps. As usedby electricians the term generally applies to the carbon filament ofincandescent lamps. This as now made has not necessarily any fibres, butis entitled to the name of filament, partly by convention, partly by itsrelative thinness and want of stiffness. (See IncandescentLamps--Magnetic Filament.)Fire Alarm, Electric, Automatic.A system of telegraph circuits, at intervals supplied with thermostatsor other apparatus affected by a change of temperature, which on beingheated closes the circuit and causes a bell to ring. (See Thermostat.)Fire Alarm Telegraph System.A system of telegraphic lines for communicating the approximate locationof a fire to a central station and thence to the separate fire-enginehouses in a city or district. It includes alarm boxes, distributed atfrequent intervals, locked, with the place where the key is keptdesignated, or in some systems left unlocked. On opening the door of thebox and pulling the handle or otherwise operating the alarm, adesignated signal is sent to the central station. From this it istelegraphed by apparatus worked by the central station operator to theengine houses. The engines respond according to the discipline of theservice.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 onwater which, escaping through the building, is supposed to reach andextinguish a fire.Flashing in a Dynamo or Magneto-electric Generator.Bad adjustment of the brushes at the commutator, or other fault ofconstruction causes the production of voltaic arcs at the commutator ofa generator, to which the term flashing is applied.Flashing of Incandescent Lamp Carbons.A process of treatment for the filaments of incandescent lamps. Thechamber 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 thenpassed through the filament heating it to redness. The more attenuatedparts or those of highest resistance are heated the highest, anddecompose most rapidly the hydro-carbon vapor, graphitic carbon beingdeposited upon these parts, while hydrogen is set free. This goes onuntil the filament is of uniform resistance throughout. It gives also away of making the resistance of the filament equal to any desired numberof ohms, provided it is originally of high enough resistance. Theprocess 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 alterationof the resistance of the circuit a long blue spark will be drawn outaround the surface of the commutator from brush to brush. The spark issomewhat of the nature of an arc, and may seriously injure commutatorswhose sections are only separated by mica, or other thin insulation. Inthe case of commutators whose sections are separated by air spaces it isnot so injurious.Flats.In a commutator of a dynamo, the burning or wearing away of a commutatorsegment to a lower level than the rest. Sometimes two adjacent bars willbe thus affected, causing a flat place on the commutator. It is notalways easy to account for the formation of flats. They may have theirorigin in periodic vibrations due to bad mounting, or to sparking at theparticular point.Floor Push.A press or push button constructed to be set into the floor to beoperated 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 goesto the negative plate. This it does by oxidizing it. Chromic acid,nitric acid, and chloric acids are among the constituents of liquiddepolarizers. (See Electropoion Fluid.)Fluid, Electric.The electric current and charge have sometimes been attributed to afluid. The theory, which never was much more than hypothetical, survivesto some extent in the single and double fluid theory. (See Single FluidTheory-Double Fluid Theory.)Fluorescence.The property of converting ether waves of one length, sometimes ofinvisible length, into waves of another length (visible). AEsculin,quinine salts, uranium glass and other substances exhibit thisphenomenon. The phenomenon is utilized in the production of Geisslertubes.Flush Boxes.A heavy iron box covered with a heavy hand plate and laid flush (whencethe name), or even with the surface of a roadway. Into it conductors ofan underground system lead, and it is used to make connections therewithand for examining the leakage of the conductors and for similarpurposes. 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. Itcarries several tangentially directed points, all pointing in the samesense. When connected with a source of electricity of high potential itrevolves by reaction. The tension of its charge is highest at thepoints, the air there is highly electrified and repelled, the reactionpushing the wheel around like a Barker's mill or Hero's steam engine.Sometimes the flyer is mounted with its axis horizontal and across therails on a railroad along which it travels.Synonym--Reaction Wheel.Foci Magnetic.The two points on the earth's surface where the magnetic intensity isgreatest. They nearly coincide in position with the magnetic poles.Fog, Electric.Fogs occurring when the atmosphere is at unusually high potential andaccompanied by frequent change of such polarity.Following Horns.In dynamo-electric machines the projecting ends of the pole piecestowards which the outer uncovered perimeter of the armature turns in itsregular operations. The leading horns are those away from which thearmature rotates. In considering rotation the exposed portion of thesuperficies of the armature is considered. The definition would have tobe 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 ata distance of one foot. The ordinary units of illuminating power areentirely relative; this is definite. It is due to Carl Herring.Foot-pound.A practical unit of work or energy. The quantity of work required toraise 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 anelevation under these conditions.Foot-step.In a dynamo with armature at the lower end of its field magnets, theplate generally of zinc, interposed between it and the iron base plateto prevent the leakage of lines of force outside of the circuit. Anydiamagnetic 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 tomotion or rest.(b) A measurable action upon a body under which the state of rest ofthat body, or its state of uniform motion in a straight line, sufferschange.(c) It may be defined by its measurement as the rate of change ofmomentum, 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 impartto a body of unit mass in a unit of time, or, callingforce, F,mass, macceleration per second awe have F = m a.The dimensions of force aremass (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 theelectro-magnetic unit of quantity. Its intensity varies with the squareof the distance. It may also be defined as electric force in theelectro-magnetic system.Its dimensions are equal tomechanical 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 orrepel each other. It is also termed electric force (not good) andelectro-motive intensity. It is the mechanical force acting upon a unitquantity of electricity. Its intensity varies with the square of thedistance.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)) / TThese dimensions are also those of potential difference.[Transcriber's Note: The image of the preceding paragraph is includedfor "clarity".]The objection to the term electric force is that it may be applied alsoto 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 ofa parallelogram of forces represent component forces and the diagonalrepresents the resultant. See Component--Resultant--Forces, Compositionof--Forces, Resolution of.Forces, Composition of.When several forces act in a different direction upon a point they maybe drawn or graphically represented as arrows or lines emanating fromthe point in the proper direction and of lengths proportional to theforce they exercise. Any two can be treated as contiguous sides of aparallelogram and the parallelogram can be completed. Then its diagonal,called the resultant, will represent the combined action of the twoforces, both as regards direction and intensity. This is the compositionof two forces.If more than two forces act upon the given point the resultant can becomposed with any of the others and a new force developed. The newresultant can be combined with another force, and the process kept up,eliminating the components one by one until a final resultant of all isobtained. This will give the exact direction and intensity of theforces, however many or varied.261 STANDARD ELECTRICAL DICTIONARY.Forces, Resolution of.The developing from a single force treated as a resultant, two otherforces in any desired direction. The reverse of composition of forces.(See Forces, Composition of--Forces, Parallelogramof--Components--Resultant.)Force, Tubes of.Aggregations of lines of force, either electrostatic or magnetic. Theygenerally have a truncated, conical or pyramidal shape and are nothollow. Every cross-section contains the same number of lines. The nameit 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 producean acceleration of one foot per second in a mass of one pound). It isequal to about 10/322 pound. A force cannot be expressed accurately inweight units, because weight varies with the latitude.Forming.The process of producing secondary battery plates from lead plates byalternately passing a charging current through the cell and thenallowing it to discharge itself and repeating the operation. (SeeBattery, Secondary, Planté's.)Foundation Ring.In a dynamo armature the ring-shaped core on which Gramme ring armaturesand 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 somewhatindependently making plasma electrically conductive. It respondsstrongly 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 akite in a thunder storm. The kite was of silk so as to endure thewetting. When the string became wet sparks could be taken from a keyattached to its end. The main string was of hemp; at the lower end was alength of silk to insulate it. The key was attached near the end of andto the hemp string.Franklin's Plate.A simple form of condenser. It consists of a plate of glass coated oneach 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 platecharged like a Leyden jar. Or one side may be connected with oneterminal, and the other with the other terminal of an influence machineand 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 analternating current.Synonym--Periodicity.Frictional Electricity.Electricity produced by friction of dissimilar substances. (SeeElectrostatic Series.) The contact theory holds that friction plays onlya secondary rôle in this process; that it increases the thoroughness ofcontact, and tends to dry the rubbing surfaces, but that the chargesinduced are due to contact of dissimilar substances, not to friction ofone against the other.Frictional Heating.The heating of a conductor by the passage of a current; the Jouleeffect, 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 currentor dynamic electricity. If a pair of legs of a recently killed frog areprepared with the lumbar nerves exposed near the base of the spinalcolumn, and if a metallic conductor, one half-length zinc and the otherhalf-length copper, is held, one end between the lumbar nerves and thespine, and the other end against one of the muscles of the thigh orlower legs, the moment contact occurs and the circuit is completedthrough the animal substance the muscles contract and the leg isviolently drawn upwards. Galvani, in 1786, first performed, by accident,this famous experiment, it is said, with a scalpel with which he wasdissecting the animal. He gave his attention to the nerves and muscles.Volta, more happily, gave his attention to the metals and invented thevoltaic battery, described by him in a letter to Sir Joseph Banks, dated1800.Frog, Rheoscopic.If the nerve or living muscle of a frog is suddenly dropped upon anotherliving muscle so as to come in contact with its longitudinal andtransverse sections, the first muscle will contract on account of thestimulation of its nerve due to the passage of a current derived fromthe 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 tooclose approach of the carbons to each other. It has been suggested thatit may be due to volatilization of the carbon. (Elihu Thomson.)Fulgurite.An irregular and tubular mass of vitrified quartz, believed to be formedby melting under the lightning stroke.Fig. 175. CRUCIBLE, ELECTRIC.Furnace, Electric.A furnace in which the heat is produced by the electric current. It hashitherto been practically used only in the extraction of aluminum andsilicium from their ores. The general principle involves the formationof an arc between carbon electrodes. The substances to be treated areexposed to the heat thus produced. Sometimes the substances in the arcform 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 isexcellent material for the tablet, as it is incombustible, and is easilydrilled and worked.Fuse Box.A box containing a safety fuse. Porcelain is an excellent material forits 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 runningfrom terminal to terminal, to whose centre a leaden ball is secured bybeing cast into position. The connection with the terminals is made byrings at the ends of the wire through which the terminal screws arepassed and screwed home. When the tin softens under too heavy a currentthe 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. Inone a thin wire unites the ends of the two conducting wires as theyenter the case of the fuse. The larger wires are secured to the case, sothat no strain comes on the fine wire. On passing a current ofsufficient strength the small wire is heated. In use the fuse is beddedin powder, which again may be surrounded by fulminating powder, allcontained in a copper or other metallic case. Such a detonator is usedfor exploding guncotton and other high explosives.The other kind of fuse is similar, but has no thin connecting wire. Theends of the conductors are brought nearer together without touching. Inuse a static discharge is produced across from end to end of theconductors, igniting a proper explosive placed there as in the othercase.The first kind of fuse is generally operated by a battery or smallmechanical generator--the latter by a spark coil, frictional orinfluence machine or by a Leyden jar.
264 STANDARD ELECTRICAL DICTIONARY.Galvanic. adj.Voltaic; relating to current electricity or the electrolytic andelectro-chemical relations of metals. (For titles in general under thishead see Voltaic--or the main title.)Galvanic Element.A galvanic couple with exciting fluid and adjuncts; a galvanic cell. Theword element is sometimes applied to the electrodes of a cell, as thecarbon 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 byelectrolysis.(b) In medical electricity the effects produced on any part of thesystem by the current of voltaic battery. Various descriptivequalifications are prefixed, such as "general" galvanization, indicatingits application as applied to the whole body, "local" for the reversecase, and so on.Galvanization, Labile.Application of the galvanic current in electro-therapeutics where onesponge electrode is employed which is rubbed or moved over the body, theother being in constant contact with the body.Galvanized Iron.Iron coated with zinc by cleaning and immersion in melted zinc. The ironis prevented from rusting by galvanic action. It forms the negativeelement in a couple of which the zinc is the positive element. From thiselectric protective action the name is derived.Galvano-cautery, Chemical.Electro-therapeutic treatment with sharp electrodes, one of which isinserted in the tissue and a current passed by completing the circuitthrough the tissue so as to electrolyze or decompose the fluids of thetissue. It is applied in the removal of hair or extirpation of thefollicle. The process is not one of heating, and is improperly namedcautery.Galvano-faradization.In medical electricity the application of the voltaic and induced orsecondary current simultaneously to any part of the system.Galvanometer.An instrument for measuring current strength and sometimes for measuringinferentially potential difference, depending on the action of amagnetic field established by the current, such action being exerted ona magnetic needle or its equivalent.A current passing through a conductor establishes circular lines offorce. A magnetic needle placed in their field is acted on and tends toplace itself parallel with the lines, in accordance with the principlesof current induction. (See Induction, Electro-magnetic.) A commoncompass held near a conductor through which a current is passing tendsto place itself at right angles to such conductor. For a maximum effectthe conductor or the part nearest the needle should lie in the magneticmeridian. If at right angles thereto its action will only strengthen thedirective force of the earth's induction or magnetic field, as theneedle naturally points north and south. Such combination is virtually agalvanometer.266 STANDARD ELECTRICAL DICTIONARY.A typical galvanometer comprises a flat coil of wire placed horizontallywithin which a magnetic needle is delicately poised, so as to be free torotate with the least possible friction. The needle may be supported ona sharp point like a compass needle, or may be suspended by a long finefilament. It should be covered by a glass plate and box, or by a glassshade. Finally a graduated disc may be arranged to show the amount ofdeflection of the needle.In use the apparatus is turned about until the needle, as acted on bythe earth's magnetic field, lies parallel to the direction of the coilsof wire. On passing a current through the coil the needle is deflected,more or less, according to its strength.By using exceedingly fine wire, long enough to give high resistance, theinstrument can be used for very high potentials, or is in condition foruse in determining voltage. By using a coil of large wire and lowresistance it can be employed in determining amperage. In either casethe deflection is produced by the current.The needle is often placed above or below the coil so as only to receivea portion of its effect, enough for all practical purposes in thecommoner class of instruments.The galvanometer was invented by Schweigger a short time after Oersted'sdiscovery, q. v.Galvanometer, Absolute.A galvanometer giving absolute readings; properly one whose law ofcalibration can be deduced from its construction. Thus the diameter ofthe coil, and the constants and position of a magnetic needle suspendedin its field being known, the current intensity required to deflect theneedle a given number of degrees could be calculated.Galvanometer, Aperiodic.A galvanometer whose needle is damped (see Damping) as, for instance, bythe proximity of a plate of metal, by an air vane or otherwise, so thatit reaches its reading with hardly any oscillation. A very light needleand a strong magnetic field also conduce to vibrations of short perioddying out very quickly. Such galvanometers are termed "dead-beat." Noinstrument is absolutely dead-beat, only relatively so.267 STANDARD ELECTRICAL DICTIONARY.Fig. 178. ASTATIC GALVANOMETER.Galvanometer, Astatic.A galvanometer with a pair of magnetic needles connected astatically, orparallel with their poles in opposition. (See Astatic Needle.) Eachneedle has its own coil, the coils being wound in opposite directions soas to unite in producing deflections in the same sense. As there shouldbe some directive tendency this is obtained by one of the magnets beingslightly stronger than the other or by the proximity of a fixed andadjustable controlling magnet, placed nearer one needle than the other.For small deflections the currents producing them are proportional totheir extent.Galvanometer, Ballistic.A galvanometer whose deflected element has considerable moment ofinertia; the exact opposite of an aperiodic or dead beat galvanometer.(See Galvanometer, Aperiodic.) All damping by air vanes or otherwisemust be carefully done away with.Fig. 179. SIEMENS & HALSKE'S GALVANOMETER.Siemens & Halske's galvanometer is of the reflecting or mirror type (seeGalvanometer, Reflecting) with suspended, bell-shaped magnet, in placeof the ordinary magnetic needle, or astatic combination of the lightestpossible weight in the regular instrument. A copper ball drilled out toadmit the magnet is used as damper in the ordinary use of theinstrument. To convert it into a ballistic galvanometer the copper ballis removed. The heavy suspended magnet then by its inertia introducesthe desired element into the instrument.268 STANDARD ELECTRICAL DICTIONARY.Referring to the cut, Fig. 179, M is the suspended magnet, with northand south poles n and s; S is the reflecting mirror; r is the tubecontaining the suspending thread; R is the damper removed for ballisticwork.The ballistic galvanometer is used to measure quantities of electricityin an instantaneous discharge, which discharge should be completedbefore the heavy needle begins to move. The extreme elongation or throwof the needle is observed, and depends (1) on the number of coulombs (K)that pass during the discharge; (2) on the moment of inertia of theneedle and attached parts; (3) on the moment of the controlling forces,i. e., the forces tending to pull the needle back to zero; (4) on themoment of the damping forces; (5) on the moment of the deflecting forcesdue to a given constant current. The formula is thus expressed:K = (P / PI ) * A * sin( kº / 2 ) / tan( aº )in which K = coulombs discharged; P = periodic time of vibration ofneedle; A = amperes producing a steady deflection equal to aº ; kº =first angular deflection of needle. For accuracy kº and aº should bothbe small and the damping so slight as to be negligible. Otherwise acorrection for the latter must be applied. For approximate work for kºand aº the deflections read on the scale may be used with the followingformula:K = (P / PI ) * ( A / 2 ) * ( kº / aº )Galvanometer Constant.Assume a galvanometer with a very short needle and so placed withrespect to its coils that the magnetic field produced by a currentcirculating in them is sensibly uniform in the neighborhood of theneedle, with its lines of force at right angles thereto. The field isproportional to the current i, so that it may be denoted by G i. Then Gis the galvanometer constant. If now the angle of deflection of theneedle is ? against the earth's field H, M being the magnetic moment ofthe needle we have G i M cos ? = H M sin ? or i = (H/G)* tan ?. H/G isthe reduction factor; variable as H varies for different places.For a tangent galvanometer the constant G is equal to 2*PI*(n/a), inwhich n denotes the number of turns of wire, and a denotes the radius ofthe circle.Galvanometer, Differential.A galvanometer in which the needle is acted on by two coils wound inopposition, each of equal deflecting action and of equal resistance. Ifa current is divided between two branches or parallel conductors, eachincluding one of the coils, when the needle points to zero theresistances of the two branches will bc equal. In the cut, C C'represent the coils, and A and B the two leads into which the circuit, PQ, is divided.269 STANDARD ELECTRICAL DICTIONARY.Fig. 180. THEORY OF DIFFERENTIAL GALVANOMETER.Fig. 181. DIFFERENTIAL GALVANOMETER.Galvanometer, Direct Reading.A calibrated galvanometer, whose scale is graduated by volts or amperes,instead of degrees.Galvanometer, Marine. (Sir William Thomson's.)A galvanometer of the reflecting type, for use on shipboard. A fibresuspension is adopted for the needle. The fibre is attached to a fixedsupport at one end and to a spring at the other, and the needle issuspended by its centre of gravity. This secures it to a considerableextent from disturbance due to the rolling of the ship. A thick iron boxencloses the needle, etc., to cut off any magnetic action from the ship.(See Galvanometer, Reflecting.)Galvanometer, Potential.A galvanometer wound with fine German silver wire to secure highresistance used for determination of potential difference.Galvanometer, Proportional.A galvanometer so constructed that the deflections of its index areproportional to the current passing. It is made by causing thedeflecting force to increase as the needle is deflected, more and more,or by causing the restitutive force to diminish under like conditions,or by both. The condition is obtained in some cases by the shape andposition of the deflecting coils.Galvanometer, Quantity.A galvanometer for determining quantities of electricity, by thedeflections produced by discharging the quantities through their coils.It is a ballistic galvanometer with very little or no damping.270 STANDARD ELECTRICAL DICTIONARY.Fig. 182. PRINCIPLE OF REFLECTING GALVANOMETER.Fig. 183. REFLECTING GALVANOMETER.Galvanometer, Reflecting.A galvanometer the deflections of whose needle are read by an imageprojected by light reflected from a mirror attached to the needle or toa vertical wire carrying the needle. A lamp is placed in front of theinstrument facing the mirror. The light of the lamp is reflected by themirror upon a horizontal scale above the lamp. An image of a slit or ofa wire may be caused thus to fall upon the scale, the mirror beingslightly convex, or a lens being used to produce the projection.271 STANDARD ELECTRICAL DICTIONARY.If the mirror swings through a horizontal arc, the reflected image willmove, in virtue of a simple geometrical principle, through an arc oftwice as many degrees. The scale can be placed far from the mirror, sothat the ray of light will represent a weightless index of very greatlength, and minute deflections of the needle will be shown distinctlyupon the scale.In the cut, Fig. 182, the ray of light from the lamp passes through theaperture, m m, and is made parallel by the lens, L. At s is the mirrorattached to the needle and moving with it. A scale placed at t receivesthe reflection from the mirror. The cut, Fig. 183, shows one form of theinstrument set up for use.Synonym--Mirror Galvanometer.Galvanometer Shunt.To prevent too much current passing through a galvanometer (for fear ofinjury to its insulation) a shunt is sometimes placed in parallel withit. The total current will be distributed between galvanometer and shuntin the inverse ratio of their respective resistances. (See MultiplyingPower of a Shunt.)272 STANDARD ELECTRICAL DICTIONARY.Fig. 184. SINE GALVANOMETER.Galvanometer, Sine.A galvanometer whose measurements depend upon the sine of the angle ofdeflection produced when the coil and needle lie in the same verticalplane.The needle, which may be a long one, is surrounded by a coil, which canbe rotated about a vertical axis passing through the point of suspensionof the needle. Starting with the needle at rest in the plane of thecoil, a current is passed through the coil deflecting the needle, thecoil is swung around deflecting the needle still more, until the needlelies in the plane of the coil; the intensity of the current will then bein proportion to the sine of the angle through which the coil and needlemove.In the galvanometer M is a circle carrying the coil, N is a scale overwhich the needles, m and n, move, the former being a magnetic needle,the latter an index at right angles and attached thereto; a and b arewires carrying the current to be measured. The circles, M and N, arecarried by a base, O, around which they rotate. H is a fixed horizontalgraduated circle. In use the circle, M, is placed in the magneticmeridian, the current is passed through the coil, M; the needle isdeflected; M is turned until its plane coincides with the direction ofthe needle, m. The current strength is proportional to the sine of theangle of deflection. This angle is measured by the vernier, C, on thecircle, H. The knob, A, is used to turn the circle, M.273 STANDARD ELECTRICAL DICTIONARY.Fig. 185. TANGENT GALVANOMETER.Galvanometer, Tangent.A galvanometer in which the tangents of the angles of deflection areproportional to the currents producing such deflections.For this law to apply the instrument in general must fulfill thefollowing conditions:(1) The needle must be controlled by a uniform magnetic field such asthat of the earth;(2) the diameter of the coil must be large compared to the length of theneedle;(3) the centre of suspension of the needle must be at the centre of thecoil;(4) the magnetic axis of the needle must lie in the plane of the coilwhen no current is passing.If a single current strength is to be measured the best results will beattained when the deflection is 45°; in comparing two currents the bestresults will be attained when the deflections as nearly as possible areat equal distances on both sides of 45°.The needle should not exceed in length one-tenth the diameter of thecoil.For very small deflections any galvanometer follows the law oftangential deflection.As for very small deflections the tangents are practically equal to thearcs subtended, for such deflections the currents are proportional tothe deflections they produce.The sensibility is directly proportional to the number of convolutionsof wire and inversely proportional to their diameter.The tangent law is most accurately fulfilled when the depth of the coilin the radial direction is to the breadth in the axial direction assquareRoot(3):squareRoot(2), or about as 11:9.Galvanometer, Torsion.A galvanometer whose needle is suspended by a long filament or by athread and spiral spring against whose force of torsion the movements ofthe needle are produced. The current strength is determined by bringingthe needle back to its position of rest by turning a hand-button orother arrangement. The angle through which this is turned gives theangle of torsion. From this the current strength is calculated on thegeneral basis that it is proportional to the angle of torsion.Fig. 186. TORSION GALVANOMETER.274 STANDARD ELECTRICAL DICTIONARY.Galvanometer, Vertical.A galvanometer whose needle is mounted on a horizontal axis and isdeflected in a vertical plane. One of the poles is weighted to keep itnormally vertical, representing the control. It is not used for accuratework.Synonym--Upright Galvanometer.Fig. 187. VERTICAL GALVANOMETER.Galvanometer, Volt- and Ampere-meter.A galvanometer of Sir William Thomson's invention embodying the tangentprinciple, and having its sensibility adjustable by moving the magneticneedle horizontally along a scale (the "meter") towards or away from thecoil. A curved magnet is used to adjust the control. The leads aretwisted to prevent induction.The instrument is made with a high resistance coil for voltagedeterminations, and with a low resistance coil for amperagedeterminations.At one end of a long base board a vertical coil with its plane at rightangles to the axis of the board is mounted. A scale (the "meter" of thename) runs down the centre of the board. A groove also runs down thecentre. The magnetic needle is contained in a quadrant-shapedglass-covered box which slides up and down the groove. A number of shortparallel needles mounted together, with an aluminum pointer are used.