413 STANDARD ELECTRICAL DICTIONARY.Fig. 260. DIAGRAM OF PRINCIPLEOF THE DISPERSION PHOTOMETER.The cut, Fig. 261, gives a perspective view of Ayrton's DispersionPhotometer. C is the standard candle, L the concave lens, R the rod forproducing the two shadows on the screen S.Fig. 261. AYRTON'S DISPERSION PHOTOMETER.The mirror M is fixed at an angle of 45° with the stem on which itrotates. The light of the arc lamp is received by the mirror and isreflected through the lens. The candle holder slides along a graduatedbar C, and at D is an index plate to show the angle at which the spindlecarrying the mirror is set.414 STANDARD ELECTRICAL DICTIONARY.Dr. J. Hopkinson in his dispersion photometer uses a double convex lens.This gives a focal image of the arc-lamp between the lens and screen,whence the rays diverge very rapidly, thus giving the desired dispersioneffect.It is principally for arc lamps that dispersion photometers are used.Photometer, Shadow.A photometer in which the relative intensity of the two lights isestimated by the intensity or strength of shadows of the same objectwhich they respectively cast.Fig. 262. RUMFORD'S SHADOW PHOTOMETER.Fig. 263. RUMFORD'S SHADOW PHOTOMETER ARRANGED FOR TESTINGINCANDESCENT LAMPS.415 STANDARD ELECTRICAL DICTIONARY.A rod is supported in a vertical position. Back of it is a screen ofwhite paper. The two lights to be compared are arranged in front of therod and at a little distance from each other. They are shifted aboutuntil the two shadows appear of equal darkness. The relative intensityof the lights varies inversely with the square of their distances fromthe shadows cast respectively by them on the screen.The cut, Fig. 262, shows the simplest type of the shadow photometer. Inthe cut, Fig. 263, a shadow photometer for testing incandescent lamps isshown. In it E is the lamp under trial supported by a clamp H. A is anampere meter in circuit with the lamp, and V is a voltmeter. A candle Ccan be moved along a graduated scale G G. R is the vertical rod, and Sis the screen on which the shadows fall.Photophore.An instrument for medical examination of the cavities of the body. Itincludes an incandescent lamp mounted in a tube with a concave mirrorand convex lens.Photo-voltaic Effect.The change in resistance of some substances effected by light. Selenium,of all substances, is most susceptible to this effect. (See Selenium.)Piano, Electric.A piano whose manual or key-board operates to close electric circuits,whereby electro-magnets are caused to operate to drive the hammersagainst the strings.Pickle.An acid solution for cleaning metal surfaces before electro-plating,galvanizing or other deposition of metal upon them.Picture, Electric.A picture produced by passing a strong discharge through a piece of goldleaf clamped or firmly pressed upon a sheet of paper. The gold leaf iscut out of the desired shape, or else a stencil of paper overlays it.The discharge dissipates the gold, and produces a purple coloredreproduction of the design upon the paper. The design is due to thedeposition of an exceedingly thin film of metallic gold.Synonym--Electric Portrait.Pile.A galvanic or voltaic battery. It is sometimes restricted to a number ofvoltaic couples connected. It should be only applied to batteries withsuperimposed plates and no containing vessel such as the Dry Pile, q.v., or Volta's Pile, q. v.Pilot Transformer.In alternating current distribution a small transformer placed at anypart of the system and connected to a voltmeter in the central station,to indicate the potential difference of the leads.Pilot Wires.Wires brought from distant parts of electric light or power mains, andleading to voltmeters at the central station, so that the potential ofdistant parts of the system can be watched. The wires can be very small,as they have but little current to transmit.416 STANDARD ELECTRICAL DICTIONARY.Pistol, Electric.An experimental apparatus for exhibiting the power of electricincandescence or of the electric spark. A tube is mounted with a handlelike a pistol. A plug is provided to screw in and out of its side. Theplug carries two wires connected on its inner side by a fine platinumwire, or else disconnected but with their ends brought near together toact as terminals for the production of a spark. To use it the tube isfilled with a mixture of air and gas, the latter either hydrogen,hydro-carbon or other combustible gas. The tube when full is corked. Thewire is heated to incandescence by a current, or a spark is passed froma Leyden jar or other source of electrostatic excitation. The mixture,if properly proportioned, explodes and expels the cork violently.Fig. 264. ELECTRIC PISTOL.Pith.A light and soft cellular tissue forming the central core of exogenoustrees and plants. In the older parts of the tree the woody tissue oftenencroaches in and partly obliterates it.For electrical pith-balls, the pith of the elder, of corn, or, best ofall, of sun-flower stems is used.Pith-balls.Ball made of pith. They are used in the construction of electroscopesand for other experiments in static electricity.They are cut out with a sharp knife and their shape may be improved bygentle rolling in the hand or between the fingers.Pivot Suspension.Suspension poising or supporting of an object on a sharp pivot. This isused for the needle in the ordinary compass. A cavity or inverted cup,which may be made of agate, is attached to the middle of the needlewhich has a hole for its reception. The centre of gravity of the needlecomes below the bottom of the cup.Pivot suspension is not perfect, as it has considerable friction. Thereis no restitution force, as with torsion filaments.417 STANDARD ELECTRICAL DICTIONARY.Plant.The apparatus for commercial manufacturing or technical works. Anelectric lighting plant includes the boilers, engines and dynamos forproducing the current, and the electric mains and subsidiary apparatus.Plant Electricity.Electricity manifested by plant life. By means of a galvanometerpotential differences are found to exist in different parts of trees orfruits. The roots and interior portions are negative, and the flowers,smaller branches and fruit are positive.In some cases a contraction of the tissue of plants can be produced byan electric current. The sensitive plant and others exhibit thisphenomenon, exactly analogous to the action of muscular tissue.Plate, Arrester.In a lightning arrester the plate connected to the circuit. Sometimesboth plates are designated arrester plates.Plate Condenser.A static condenser having a flat plate of glass for dielectric. (SeeEpinus' Condenser.)Plate Electrical Machine.A frictional electric machine, in which a circular plate of glass isexcited by friction with the cushions. It is the most recent type offrictional machine and has superseded the old cylinder machines. In itsturn it is superseded by influence machines, really plate machines, butnot so termed in practice.Plate, Ground.In a lightning arrester, the plate connected to the earth.Plate, Negative.In a voltaic battery, either primary or secondary, the plate which isunattacked by the oxygen or negative radical or element of the fluid. Itcorresponds to the carbon plate in the ordinary voltaic battery, and isthe one charged with positive electricity.Plate, Positive.In a voltaic battery, either primary or secondary, the plate which isdissolved or attacked by the oxygen or negative radical or element ofthe fluid. It is the plate corresponding to the zinc plate in theordinary voltaic battery, and is the one charged with negativeelectricity.Plating Balance.A balance or scales to which articles in an electroplater's bath aresuspended. A weight exceeding by a known amount that of the article asimmersed overbalances the article. When the plating is being depositedas soon as it exceeds the excess of weight of the counterpoise thebalance tips, the article descends a little, the electric circuit isbroken and the plating ceases. Thus the plating is automatically stoppedwhen a predetermined amount of metal is deposited.418 STANDARD ELECTRICAL DICTIONARY.Plating Bath.A vessel of solution for the deposition of metal by electrolysis as usedin electro-plating.Plating, Electro-.The deposition of metal by electrolysis so as to coat the conductingsurface of objects therewith. The full details of the many processes arevery lengthy and cannot be given here.The general principle includes a battery or source of electric current.The object to be plated is connected to the negative terminal and isimmersed in the solution. Thus with a battery the object is inelectrical connection with the zinc plate. To the other terminal ametallic plate is connected. The object and the plate termed the anodebeing introduced into a suitable bath, the metal whose solution is inthe bath is deposited upon the surface of the object.The bath is a solution of the metal in some form that will lend itselfto the electrolytic action. The anode is often a plate of the metal ofthe bath, so that it dissolves as fast as metal is deposited on theobject, thus keeping up the strength of the solution.The objects to be plated must be scrupulously clean, and great care mustbe taken to keep the bath uncontaminated.When the object has a non-conducting surface, it is made conducting bybeing brushed over with plumbago q.v. In addition iron dust is sometimesdusted over it. This acts by precipitating the metal of the bathdirectly and thus giving a conducting basis for the metal to deposit on.To avoid getting iron in a bath the object may be dipped in coppersulphate solution. This precipitates copper in place of the iron andleaves the article in good shape for silver or other plating.Electro-plating, if made thick enough, gives a reverse of the articlewhen separated therefrom. A direct copy can be got by a second plating,on the first plating after separation, or a wax impression can beemployed.Under the different metals, formulae for the baths will be found. (Seealso Quicking--Steeling--Plating Balance.)Platinoid.An alloy of copper, nickel, zinc in the proportions of German silverwith 1 or 2 per cent of tungsten. It is used for resistances. It has aspecific resistance (or resistance per centimeter cube) of about 34microhms. Its percentage variation in resistance per degree C. (1.8° F.)is only about .021 per cent., or less than half that of German silver.This is its most valuable feature.419 STANDARD ELECTRICAL DICTIONARY.Platinum.A metal; one of the elements; symbol, Pt; atomic weight, 197.4;equivalent, 49.35; valency, 4; specific gravity, 21.5.It is a conductor of electricity.The following data refer to the annealed metal at 0° C. (32° F.)Relative Resistance (Silver annealed = 1), 6.022Specific Resistance, 9.057 microhms.Resistance of a wire,(a) 1 foot long, weighing 1 grain, 2.779 ohms.(b) 1 foot long, 1/1000 inch thick, 54.49 "(c) 1 meter long, weighing 1 gram, 1.938 "(d) 1 meter long, 1 millimeter thick, .1153 "Resistance of a 1 inch cube, 3.565Electro-chemical equivalent (Hydrogen = .0105), 0.5181.The coefficient of expansion by heat is almost the same as that ofglass. It can be passed through holes in glass and the latter can bemelted about it so as to hermetically seal its place of passage throughthe glass. It is used in incandescent lamps for leading-in wires andother similar uses.Platinum Black.Finely divided platinum. It is made by boiling a solution of platinicchloride with excess of sodium carbonate and a quantity of sugar, untilthe precipitate is perfectly black and the supernatant liquid iscolorless. It seems to possess a great power of occluding oxygen gas.When heated to redness it becomes spongy platinum. The negative platesof a Smee battery are coated with platinum black.Platinum-silver Alloy.An alloy of 1 part platinum and 2 parts silver, used for resistance coils.Relative Resistance (silver annealed = 1 ), 16.21 microhms.Specific Resistance at 0°C. (32° F.), 24.39Resistance of a wire,(a) 1 foot long, weighing 1 grain, 4.197 ohms.(b) 1 foot long, 1/1000 inch diameter, 146.70 "(c) 1 meter long weighing 1 gram, 2.924 "(d) 1 meter long, 1 millimeter diameter, 0.3106 "Resistance of a 1 inch cube, 9.603 microhms.Percentage Variation per degree C. (1.8° F.)at about 20° C. (68° F.), 0.031 per cent.Synonym--Platinum Alloy.Platinum Sponge.Finely divided platinum obtained by igniting platinum black, q.v., andalso by igniting salts of platinum. It has considerable power ofcondensing or occluding oxygen. It will, if in good condition, set fireto a jet of hydrogen impinging upon it.Plow.Contact arms projecting downwards from the motors, trucks, or bodies ofelectric street cars, which enter the underground conduit through theslot and carry contact pieces or brushes, to take the current fordriving the motors from the leads within the conduit.420 STANDARD ELECTRICAL DICTIONARY.Plücker Tubes.A special form of Geissler tube designed for the production ofstratification and for observing the effects produced in the spacesurrounding the negative electrode.Plug.(a) A piece of metal with a handle and a somewhat tapered end, used tomake connections by insertions between two plates or blocks of metalslightly separated and with grooves to receive it.(b) A plug or wedge with two metallic faces, insulated from each otherwith a separate wire connected to each one. It is used in spring-jacksq. v., to introduce a loop in a circuit.Synonym--Wedge.Plug. v.To connect by inserting a plug, as in a resistance box.Fig. 265. PLUGS FOR RESISTANCE COIL BOX.Fig. 266. PLUG SWITCH.Plug, Double.A spring-jack plug or wedge with two pairs of insulated faces, onebehind the other, so as to simultaneously introduce two loops into acircuit.Plug, Grid.A piece or mass of lead oxide, inserted into the holes in the leadplates of storage batteries. The holes are often dovetailed or of unevensection to better retain the plugs.Plug Infinity.In a box-bridge or resistance box, a plug whose removal from between twodisconnected discs opens the circuit. All the other discs are connectedby resistance coils of various resistance.Plug Switch.A switch composed of two contact blocks, not touching each other andbrought into electrical connection by the insertion of a metallic plug.The latter is usually provided with an insulating handle, and a seat isreamed out for it in the two faces of the contact blocks.421 STANDARD ELECTRICAL DICTIONARY.Plumbago.Soft lustrous graphite, a native form of carbon; sometimes chemicallypurified. It is used in electro-plating to give a conducting surface tonon-conducting objects, such as wax moulds. The surface, after coatingwith plumbago, is sometimes dusted over with iron dust, whichprecipitates the metal of the bath and starts the plating. It issometimes plated with copper, silver or gold, and is then termedcoppered, silvered, or gilt plumbago. It is gilded by moistening withetherial solution of gold chloride and exposing to the air, and dryingand igniting.Plunger.A movable core which is used in connection with a so-called solenoidcoil, to be drawn in when the coil is excited. (See Coil and Plunger.)Fig. 267 COIL AND PLUNGER WITHSCALES TO SHOW ATTRACTION.P. O.Abbreviation for Post Office, q.v.Poggendorf's Solution.An acid depolarizing and exciting fluid for zinc-carbon batteries. Thefollowing is its formula: Water, 100 parts; potassium bichromate, 12parts; concentrated sulphuric acid, 25 parts. All parts by weight. Usecold.Point, Neutral.(a) On a commutator of a dynamo the points at the ends of the diameterof commutation, or where the brushes rest upon the surface of thecommutator, are termed neutral points. At these points there is nogeneration of potential, they marking the union of currents of oppositedirection flowing from the two sides of the armature into the brushes.(b) In electro-therapeutics, a place in the intra-polar region of anerve so situated with reference to the kathode and electrode as appliedin treatment, that its condition is unaffected.Synonym--Indifferent Point.(c) In a magnet the point of no attraction, situated between the twopoles, at about an equal distance from each, so as to mark the centre ofa magnet of even distribution of polarity.(d) In thermo-electricity the point of temperature where thethermo-electric powers of two metals are zero; in a diagram the pointwhere the lines representing their thermo-electric relations cross eachother; if the metals are arranged in a thermo-electric couple, one endat a temperature a given amount above, the other at a temperature thesame amount below the neutral point, no current or potential differencewill be produced.422 STANDARD ELECTRICAL DICTIONARY.Point, Null.A nodal point in electrical resonators; a point where in a system ofwaves or oscillations, there is rest, the zero of motion being theresultant of oppositely directed and equal forces. In electricalresonators it is to be sought for in a point symmetrically situated,with reference to the spark gap, or in a pair of points, which pair issymmetrically placed.The null point in resonators is found by connecting a lead from one ofthe secondary terminals of an induction coil to different parts of theresonator. The null point is one where the connection does not give riseto any sparks between the micrometer knobs or spark gap, or where thesparks are of diminished size.The whole is exactly comparable to loops and nodes in a vibrating stringor in a Chladni plate as described in treatises on sound and acoustics.(See Resonance, Electrical--Resonator, Electrical.)Synonym--Nodal Point.Point Poles.Magnet poles that are virtually points, or of no magnitude. A long thinmagnet with little leakage except close to the ends may be supposed tohave point poles within itself a short distance back from the ends.Points, Consequent.In a magnet with consequent poles, the points where such poles aresituated.Points, Corresponding.In bound electrostatic charges the points of equal charges of oppositepotentials; the points at opposite extremities of electrostatic lines offorce. This definition implies that the bound charges shall be on equalfacing areas of conductors, as otherwise the spread or concentration ofthe lines of force would necessitate the use of areas of sizeproportionate to the spreading or concentrating of the lines of force.At the same time it may figuratively be applied to these cases, thepenetration of the surface by a single line of force including the areafixed by its relation to the surrounding lines.Points, Isoelectric.In electro-therapeutics, points of equal potential in a circuit.423 STANDARD ELECTRICAL DICTIONARY.Points of Derivation.The point where a single conductor branches into two or more conductors,operating or acting in parallel with each other.Polar Angle.The angle subtended by one of the faces of the pole pieces of the field-magnet of a dynamo or motor. The centre of the circle of the angle liesin the axis of the armature.Synonym--Angle of Polar Span.Polar Extension.An addition made of iron to the poles of magnets. Various forms havebeen experimented with. The pole pieces of dynamo field magnets arepolar extensions.Synonyms--Pole Piece--Polar Tips.Polarity, Diamagnetic.The induced polarity of diamagnetic substances; it is the reverse ofparamagnetic polarity, or of the polarity of iron. A bar of diamagneticmaterial held parallel with the lines of force in a magnetic field has alike pole induced in the end nearest a given pole of the field magnet,and vice versa. This theory accounts for the repulsion by a magnet of adiamagnetic substance. The existence of this polarity is rather anassumption. It originated with Faraday.Polarity, Paramagnetic.The induced polarity of paramagnetic substances, such as iron, nickel,or cobalt.When such a substance is brought into a magnetic field the part nearesta specific pole of a magnet acquires polarity opposite to that of suchpole and is thereby attracted.Another way of expressing it, in which the existence of a pole in ornear to the field is not implied, is founded on the conventionaldirection of lines of force. Where these enter the substance a southpole is formed and where they emerge a north pole is formed.Such polarity tends always to be established in the direction ofgreatest length, if the body is free to rotate.424 STANDARD ELECTRICAL DICTIONARY.Polarization.(a) The depriving of a voltaic cell of its proper electro-motive force.Polarization may be due to various causes. The solution may becomeexhausted, as in a Smee battery, when the acid is saturated with zincand thus a species of polarization follows. But the best definition ofpolarization restricts it to the development of counter-electro-motiveforce in the battery by the accumulation of hydrogen on the negative(carbon or copper) plate. To overcome this difficulty many methods areemployed. Oxidizing solutions or solids are used, such as solution ofchromic acid or powdered manganese dioxide, as in the Bunsen andLeclanché batteries respectively; a roughened surface of platinum blackis used, as in the Smee battery; air is blown through the solution tocarry off the hydrogen, or the plates themselves are moved about in thesolution.(b) Imparting magnetization to a bar of iron or steel, thus making apermanent magnet, is the polarization of the steel of which it is made.Polarization may be permanent, as in steel, or only temporary, as insoft iron.(c) The strain upon a dielectric when it separates two oppositelycharged surfaces. The secondary discharge of a Leyden jar, and itsalteration in volume testify to the strain put upon it by charging.(d) The alteration of arrangement of the molecules of an electrolyte bya decomposing current. All the molecules are supposed to be arrangedwith like ends pointing in the same direction, positive ends facing thepositively-charged plate and negative ends the negatively-charged one.(e) The production of counter-electro-motive force in a secondarybattery, or in any combination capable of acting as the seat of suchcounter-electro-motive force. (See Battery, Secondary--Battery, Gas.)The same can be found often in organized cellular tissue such as that ofmuscles, nerves, or of plants. If a current is passed through this inone direction, it often establishes a polarization or potentialdifference that is susceptible of giving a return current in theopposite direction when the charging battery is replaced by a conductor.Polarization Capacity.A voltaic cell in use becomes polarized by its negative plateaccumulating hydrogen, or other cause. This gradually gives the plate apositive value, or goes to set up a counter-electro-motive force. Thequantity of electricity required to produce the polarization of abattery is termed its Polarization Capacity or Capacity of Polarization.Polarization of the Medium.The dielectric polarization, q. v., of a dielectric, implying thearrangement of its molecules in chains or filaments; a term due toFaraday. He illustrated it by placing filaments of silk in spirits ofturpentine, and introduced into the liquid two conductors. Onelectrifying one and grounding (or connecting to earth) the other one,the silk filaments arranged themselves in a chain or string connectingthe points of the conductors.Polar Region.That part of the surface of a magnet whence the internal magnetic linesemerge into the air. (S. P. Thompson.) As such lines may emerge fromvirtually all parts of its surface, the polar regions are indefiniteareas, and are properly restricted to the parts whence the lines emergein greatest quantity.Polar Span.A proportion of the circle which represents the transverse section ofthe armature space between the pole pieces of the field magnet in adynamo or motor; it is the proportion which is filled by the faces ofthe pole pieces.425 STANDARD ELECTRICAL DICTIONARY.Pole, Analogous.The end of a crystal of a pyroelectric substance, such as tourmaline,which end when heated become positively electrified. On reduction oftemperature the reverse effect obtains.Pole, Antilogous.The end of a crystal of a pyroelectric substance, such as tourmaline,which end, while increasing in temperature, becomes negativelyelectrified. During reduction of its temperature the reverse effectobtains.Pole Changer.(a) An automatic oscillating or vibrating switch or contact-breakerwhich in each movement reverses the direction of a current from abattery or other source of current of fixed direction, as such currentgoes through a conductor.(b) A switch moved by hand which for each movement effects the aboveresult.Pole, Negative.(a) In a magnet the south pole; the pole into which the lines of forceare assumed to enter from the air or outer circuit.(b) In a current generator the pole or terminal into which the currentis assumed to flow from the external circuit. It is the negativelycharged terminal and in the ordinary voltaic battery is the terminalconnected to the zinc or positive plate.Pole Pieces.The terminations of the cores of field or other electro-magnets, or ofpermanent magnets. These terminations are variously shaped, sometimesbeing quite large compared to the core proper of the magnet.They are calculated so as to produce a proper distribution of anddirection of the lines of force from pole to pole. As a general rule theactive field should be of uniform strength and the pole pieces may be ofcontour calculated to attain this end.Pole, Positive.(a) In a magnet the north pole; the pole from which lines of force areassumed to emerge into the air.(b) In a current generator the pole or terminal whence the current isassumed to issue into the outer circuit. It is the positively chargedterminal, and in the ordinary voltaic battery is the terminal connectedto the copper or carbon plate, termed the negative plate.Poles.(a) The terminals of an open electric circuit, at which therenecessarily exists a potential difference, produced by the generator orsource of electro-motive force in the circuit.(b) The terminals of an open magnetic circuit; the ends of a magnetizedmass of steel, iron or other paramagnetic substance.(c) The ends in general of any body or mass which show electric ormagnetic properties more developed than those of the central sections ofthe body.426 STANDARD ELECTRICAL DICTIONARY.Pole, Salient.In dynamo and motor field magnets, salient poles are those projectingfrom the base or main body of the field magnet, as distinguished fromconsequent poles formed by coils wound on the main body itself.Fig. 268. SALIENT POLES OF FIELD MAGNET.Poles, Compensating.A device for avoiding the cross-magnetizing effect on the commutatorcore due to the lead of the brushes. It consists in maintaining a smallbar electro-magnet perpendicularly between the pole pieces. Thiscompensates the cross-magnetizing effect.Poles of Intensity.The locus of highest magnetic force on the earth's surface. One suchpole is in Siberia, another is about lat. 52° N., long. 92° W.[Transcriber's note: 52° N., long. 92° W is about 250 miles Northeast ofWinnipeg.]Poles of Verticity.The magnetic poles of the earth. (See Magnetic Poles.)Pole Tips.The extreme ends of the expanded poles of a field magnet. In somemachines some of the pole tips are made of cast iron, to alter thedistribution of the lines of force and resulting magnetic pull upon thearmatures. This is done to take off the weight of the armature from itsbearings.Pole, Traveling.A term applied to the poles produced in the action of a rotatory field,whose poles constantly rotate around the circle of the field. (SeeField, Rotatory.)417 STANDARD ELECTRICAL DICTIONARY.Porous Cup.A cup of pipe clay, unglazed earthenware or other equivalent materialused in voltaic cells to keep two liquids separate and yet to permitelectrolysis and electrolytic conduction.They are necessarily only an expedient, as their porous nature permitsconsiderable diffusion, and were they not porous electrolytic actionwould be impossible.Synonym--Porous Cell.Porret's Phenomenon.In electro-physiology, an increase in the diameter of a nerve producedby the positive pole of a voltaic circuit, when placed in contact withthe tissue and near to the nerve in question, the other pole beingconnected to a more or less remote part of the body.Portelectric Railroad.A railroad worked by solenoidal attraction, the car forming the core ofthe solenoids. It includes a series of solenoids or hollow coils ofcopper wire distributed all along the road and inclosing withinthemselves the track. On this a cylindrical car with pointed ends moveson wheels. Current is supplied to the solenoid in advance of the car,and attracts it. As it advances it breaks the contacts of the attractingsolenoid and turns the current into the one next in advance. Thisoperation is repeated as the car advances.The solenoids are placed close together, each including in the trialtrack 630 turns of No. 14 copper wire. The car was of wrought iron, 12feet long, 10 inches in diameter and weighing 500 lbs. It was proposedto employ the system for transportation of mail matter and similar uses.Position Finder.An instrument for determining the position of objects which are to befired at from forts. It is designed for use from forts situated on thewater.Fiske's position finder may be thus generally described. On a chart thechannel is divided into squares, and the position finder determines thesquare in which a vessel lies. For each square the direction andelevation of the guns is calculated beforehand. The enemy can thereforebe continuously located and fired at, although from smoke or other causethe object may be quite invisible to the gunner.It comprises two telescopes situated at distant extremities of as long abase line as is obtainable. These telescopes are kept directed upon theobject by two observers simultaneously. The observers are in constanttelephonic communication. As each telescope moves, it carries a contactover an arc of conducting material. Below each telescope is an arm alsomoving over an arc of conducting material. These arcs enter into aWheatstone bridge and are so connected that when the arm and the distanttelescope are at the same angle or parallel a balance is obtained. Thuseach observer has the power of establishing a balance. A chart isprovided for each of them, and over it the arm connected with thedistant telescope and an arm or indicator attached to the telescope atthat station move so that as long as both telescopes point at the objectand each observer maintains the electric balance, the intersection ofthe arms shows the position on the chart.The Position Finder is a simplification and amplification of the RangeFinder, q. v. In practice the observers may be placed far from theforts, and may telephone their observations thereto. It has been foundaccurate within one-third of one per cent.428 STANDARD ELECTRICAL DICTIONARY.Positive Direction.The direction which lines of force are assumed to take in the air orouter circuit from a positive to a negative region. It applies toelectrostatic, to magnetic and to electro-magnetic lines of force.Positive Electricity.The kind of electricity with which a piece of glass is charged whenrubbed with silk; vitreous electricity.In a galvanic cell the surface of the copper or carbon plate is chargedwith positive electricity. (See Electrostatic Series.)According to the single fluid theory positive electrification consistsin a surplus of electricity.[Transcriber's note: "Positive electricity" is a deficiency of electrons.]Post Office. adj.Many pieces of electric apparatus of English manufacture are thusqualified, indicating that they are of the pattern of the apparatus usedby the British Post Office in its telegraph department.Potential.Potential in general may be treated as an attribute of a point in space,and may express the potential energy which a unit mass would have ifplaced at that point.This conception of potential is that of a property attributable to apoint in space, such that if a unit mass were placed there the forcesacting upon it would supply the force factor of energy, while the bodywould supply the mass factor. This property is expressible in units,which produce, if the supposed mass is a unit mass, units of work orenergy, but potential itself is neither.Thus taking gravitation, a pound mass on the surface of the earth(assuming it to be a sphere of 4,000 miles radius) would require theexpenditure of 21,120,000 foot pounds to remove it to an infinitedistance against gravity. The potential of a point in space upon thesurface of the earth is therefore negative and is represented by-21,120,000*32.2 foot poundals (32.2 = acceleration of gravity). (SeePoundal.) In practice and conventionally all points on the earth'ssurface are taken as of zero potential.[Transcriber's note; 21,120,000 foot pounds is about 8 KWh.]429 STANDARD ELECTRICAL DICTIONARY.Potential, Absolute.The absolute electrical potential at a point possesses a numerical valueand measures the tendency which the existing electric forces would haveto drive an electrified particle away from or prevent its approach tothe point, if such a particle, one unit in quantity, were brought up toor were situated at that point. It is numerically equal to the number ofergs of work which must be done to bring a positive unit of electricityfrom a region where there is absolutely no electric force up to thepoint in question. (Daniell.) Two suppositions are included in this. Theregion where there is an electric force has to be and only can be at aninfinite distance from all electrified bodies. The moving of theparticle must take place without any effect upon the distribution ofelectricity on other particles.Potential, Constant.Unchanging potential or potential difference.The ordinary system of incandescent lighting is a constant potentialsystem, an unvarying potential difference being maintained between thetwo leads, and the current varying according to requirements.Potential Difference, Electric.If of any two points the absolute potentials are determined, thedifference between such two expresses the potential difference.Numerically it expresses the quantity of work which must be done toremove a unit of electricity from one to the other against electricrepulsion, or the energy which would be accumulated in moving it theother way.A positively charged particle is driven towards the point of lowerpotential. A negatively charged body is driven in the reverse direction.Potential Difference, Electro-motive.A difference of potential in a circuit, or in part of a circuit, whichdifference produces or is capable of producing a current, or is due tothe flow of such current.It may be expressed as the fall in potential or the electro-motive forceincluded between any two points on a circuit. The current in an activecircuit is due to the total electro-motive force in the circuit. This isdistributed through the circuit in proportion to the resistance of itsparts. Owing to the distribution of electro-motive force throughout acircuit including the generator, the terminals of a generator on closedcircuit may show a difference of potential far lower than theelectro-motive force of the generator on closed circuit. Hence potentialdifference in such a case has been termed available electro-motiveforce.Potential, Electric Absolute.The mathematical expression of a property of a point in space, measuringthe tendency which existing electric forces would have to drive anelectrified unit particle away from or prevent its approach to the pointin question, according to whether the point was situated at or was at adistance from the point in question.Potential is not the power of doing work, although, as it is expressedalways with reference to a unit body, it is numerically equal to thenumber of ergs of work which must be done in order to bring a positiveunit of electricity from a region where there is no electricforce--which is a region at an infinite distance from all electrifiedbodies--up to the point in question. This includes the assumption thatthere is no alteration in the general distribution of electricity onneighboring bodies. (Daniell.)In practice the earth is arbitrarily taken as of zero electric potential.430 STANDARD ELECTRICAL DICTIONARY.Potential, Fall of.The change in potential between any two points on an active circuit. Thechange in potential due to the maintenance of a current through aconductor.The fall in potential multiplied by the current gives work or energyunits.The fall of potential in a circuit and its subsequent raising by theaction of the generator is illustrated by the diagram of a helix. In itthe potential fall in the outer circuit is shown by the descent of thehelix. This represents at once the outer circuit and the fall ofpotential in it. The vertical axis represents the portion of the circuitwithin the battery or generator in which the potential by the action ofthe generator is again raised to its original height.In a circuit of even resistance the potential falls evenly throughoutit.A mechanical illustration of the relation of fall of potential tocurrent is shown in the cut Fig. 269. A vertical wire is supposed to befixed at its upper end and a lever arm and cord at its lower end, withweight and pulley imparts a torsional strain to it. The dials andindexes show a uniform twisting corresponding to fall of potential. Foreach unit of length there is a definite loss of twisting, correspondingto fall of potential in a unit of length of a conductor of uniformresistance. The total twisting represents the total potentialdifference. The weight sustained by the twisting represents the currentmaintained by the potential difference. For a shorter wire less twistingwould be needed to sustain the weight, as in a shorter piece of theconductor less potential difference would be needed to maintain the samecurrent.Fig. 269. MECHANICAL ILLUSTRATION OFFALL OF POTENTIAL AND CURRENT STRENGTH.431 STANDARD ELECTRICAL DICTIONARY.Fig. 270. ILLUSTRATION OF THE FALL ANDREDEVELOPMENT OF POTENTIAL IN AN ELECTRIC CIRCUIT.The fall of potential in a circuit in portions of it is proportional tothe resistance of the portions in question. This is shown in thediagram. The narrow lines indicate high and the broad lines lowresistance. The fall in different portions is shown as proportional tothe resistance of each portion.Fig. 271. DIAGRAM OF FALL OF POTENTIAL IN ACONDUCTOR OF UNEVEN RESISTANCE.Potential, Magnetic.The magnetic potential at any point of a magnetic field expresses thework which would be done by the magnetic forces of the field on apositive unit of magnetism as it moves from that point to an infinitedistance therefrom. The converse applies to a negative unit.It is the exact analogue of absolute electric potential.The potential at any point due to a positive pole m at a distance r ism/r;. that due to a negative pole - m at a distance r' is equal to-m/r';. that due to both is equal to m/r - m/r' or m(1/r - 1/r').Like electric potential and potential in general, magnetic potentialwhile numerically expressing work or energy is neither, although oftendefined as such.432 STANDARD ELECTRICAL DICTIONARY.Potential, Negative.The reverse of positive potential. (See Potential, Positive.)Potential, Positive.In general the higher potential. Taking the assumed direction of linesof force, they are assumed to be directed or to move from regions ofpositive to regions of negative potential. The copper or carbon plate ofa voltaic battery is at positive potential compared to the zinc plate.Potential, Unit of Electric.The arbitrary or conventional potential--or briefly, the potential of apoint in an electric field of force--is, numerically, the number of ergsof work necessary to bring a unit of electricity up to the point inquestion from a region of nominal zero potential--i. e., from thesurface of the earth. (Daniell.) This would give the erg as the unit ofpotential.Potential, Zero.The potential of the earth is arbitrarily taken as the zero of electricpotential.The theoretical zero is the potential of a point infinitely distant fromall electrified bodies.Fig. 272. DIAGRAM OF POTENTIOMETER CONNECTIONS.Potentiometer.An arrangement somewhat similar to the Wheatstone Bridge for determiningpotential difference, or the electro-motive force of a battery. Ingeneral principle connection is made so that the cell under trial wouldsend a current in one direction through the galvanometer. Anotherbattery is connected, and in shunt with its circuit the battery undertrial and its galvanometer are connected, but so that its current is inopposition. By a graduated wire, like that of a meter bridge, thepotential of the main battery shunt can be varied until no currentpasses. This gives the outline of the method only.433 STANDARD ELECTRICAL DICTIONARY.In the cut A B is the graduated potentiometer wire through which acurrent is passed in the direction of the arrow. E is the battery undertrial, placed in opposition to the other current, with a galvanometernext it. Under the conditions shown, if the galvanometer showed nodeflection, the E. M. F. of the battery would be to the E. M. F. betweenthe ends of the potentiometer wire, 1 . . . . .10, as 1.5 the distancebetween the points of connection, A and D of the battery circuit, is to10, the full length of the potentiometer wire.Poundal.The British unit of force; the force which acting on a mass of one poundfor one second produces an acceleration of one foot.[Transcriber's note: The force which acting on a mass of one poundproduces an acceleration of ONE FOOT PER SECOND PER SECOND.]Power. Activity;the rate of activity, of doing work, or of expending energy. Thepractical unit of electric power is the volt-ampere or watt, equal to1E7 ergs per second. The kilowatt, one thousand watts or volt-amperes,is a frequently adopted unit.Power, Electric.As energy is the capacity for doing work, electric energy is representedby electricity in motion against a resistance. This possesses a speciesof inertia, which gives it a species of kinetic energy. To produce suchmotion, electro- motive force is required. The product of E. M. F. byquantity is therefore electric energy. (See Energy, Electric.)Generally the rate of energy or power is used. Its dimensions are( ( (M^.5)*(L^.5) ) / T ) * ( ( (M^.5) *(L^1.5) )/( T^2) )(intensity or current rate) * (electro-motive force or potential)= (M * (L^2) ) / (T^3),which are the dimensions of rate of work or activity. The practical unitof electric rate of energy or activity is the volt-ampere or watt. ByOhm's law, q. v., we have C = E/R (C = current; E = potential differenceor electro-motive force; R = resistance.) The watt by definition = C*E.By substitution from Ohm's formula we deduce for it the followingvalues: ((C^2) * R) and ((E^2) /R). From these three expressions therelations of electric energy to E.M.F., Resistance, and Current can bededuced.Power of Periodic Current.The rate of energy in a circuit carrying a periodic current. In such acircuit the electro-motive force travels in advance of the current itproduces on the circuit. Consequently at phases or intervals where,owing to the alternations of the current, the current is at zero, theelectro-motive force may be quite high. At any time the energy rate isthe product of the electro-motive force by the amperage. To obtain thepower or average rate of energy, the product of the maximumelectro-motive force and maximum current must be divided by two andmultiplied by the cosine of the angle of lag, which is the angleexpressing the difference of phase.[Transcriber's note; The voltage phase will lead if the load isinductive. The current phase will lead if the load is capacitive.Capacitors or inductors may be introduced into power lines to correctthe phase offset introduced by customer loads.]434 STANDARD ELECTRICAL DICTIONARY.Pressel.A press-button often contained in a pear-shaped handle, arranged forattachment to the end of a flexible conductor, so as to hang thereby. Bypressing the button a bell may be rung, or a distant lamp may belighted.Pressure.Force or stress exerted directly against any surface. Its dimensions areforce/area or ((M*L)/(T^2)) / (L^2) = M/(L* (T^2)).Pressure, Electric.Electro-motive force or potential difference; voltage. An expression ofmetaphorical nature, as the term is not accurate.Pressure, Electrification by.A crystal of Iceland spar (calcium carbonate) pressed between thefingers becomes positively electrified and remains so for some time.Other minerals act in a similar way. Dissimilar substances pressedtogether and suddenly separated carry off opposite charges. This isreally contact action, not pressure action.Primary.A term used to designate the inducing coil in an induction coil ortransformer; it is probably an abbreviation for primary coil.Primary Battery.A voltaic cell or battery generating electric energy by directconsumption of material, and not regenerated by an electrolytic process.The ordinary voltaic cell or galvanic battery is a primary battery.Prime. vb.To impart the first charge to one of the armatures of a Holtz or otherinfluence machine.Fig. 273. PRIME CONDUCTOR AND PROOF PLANE.435 STANDARD ELECTRICAL DICTIONARY.Prime Conductor.A metal or metal coated sphere or cylinder or other solid with roundedends mounted on insulating supports and used to collect electricity asgenerated by a frictional electric machine.According to whether the prime conductor or the cushions are groundedpositive or negative electricity is taken from the ungrounded part.Generally the cushions are grounded, and the prime conductor yieldspositive electricity.Probe, Electric.A surgeon's probe, designed to indicate by the closing of an electriccircuit the presence of a bullet or metallic body in the body of apatient.Two insulated wires are carried to the end where their ends are exposed,still insulated from each other. In probing a wound for a bullet if thetwo ends touch it the circuit is closed and a bell rings. If a bone istouched no such effect is produced. The wires are in circuit with anelectric bell and battery.Projecting Power of a Magnet.The power of projecting its lines of force straight out from the poles.This is really a matter of magnetic power, rather than of shape of themagnet. In electromagnets the custom was followed by making them long toget this effect. Such length was really useful in the regard of gettingroom for a sufficient number of ampere turns.436 STANDARD ELECTRICAL DICTIONARY.Fig. 274. PRONY BRAKE.Prony Brake.A device for measuring the power applied to a rotating shaft. Itconsists of a clamping device to be applied more or less rigidly to theshaft or to a pulley upon it. To the clamp is attached a lever carryinga weight. The cut shows a simple arrangement, the shaft A carries apulley B to which the clamp B1 B2 is applied. The nuts C1 C2 are usedfor adjustment.A weight is placed in the pan E attached to the end of the lever D. Theweight and clamp are so adjusted that the lever shall stand horizontallyas shown by the index E. If we call r the radius of the pulley and F thefriction between its surface and the clamp, it is evident that r F, themoment of resistance to the motion of the pulley, is equal to the weightmultiplied by its lever arm or to W*R, where W indicates the weight andR the distance of its point of application from the centre of the pulleyor r*F = R*W. The work represented by this friction is equal to thedistance traveled by the surface of the wheel multiplied by thefrictional resistance, or is 2*PI*r*n*F, in which n is the number ofturns per minute. But this is equal to 2*PI*R*W. These data being known,the power is directly calculated therefrom in terms of weight and feetper minute.Proof-plane.A small conductor, usually disc shaped, carried at the end of aninsulating handle. It is used to collect electricity by contact, fromobjects electrostatically charged. The charge it has received is thenmeasured (see Torsion Balance) or otherwise tested. (See PrimeConductor.)Proof-sphere.A small sphere, coated with gold-leaf or other conductor, and mounted onan insulated handle. It is used instead of a proof-plane, for testingbodies whose curvature is small.Fig. 275. BOX BRIDGE.437 STANDARD ELECTRICAL DICTIONARY.Proportionate Arms.In general terms the arms of a Wheatstone bridgewhose proportion has to be known to complete the measurement. There is adifferent system of naming them. Some designate by this title the twoarms in parallel with each other branching at and running from one endof the bridge to the two galvanometer connections. In the cut of the BoxBridge, A C and A B are the proportionate arms. The third arm is thentermed the Rheostat arm. (Stewart & Gee.)Others treat as proportionate arms the two side members of the bridge inparallel with the unknown resistance and third or rheostat arm.Synonym--Ratio Arms.Prostration, Electric.Too great exposure to the voltaic arc in its more powerful forms causessymptoms resembling those of sunstroke. The skin is sometimes affectedto such a degree as to come off after a few days. The throat, foreheadand face suffer pains and the eyes are irritated. These effects onlyfollow exposure to very intense sources of light, or for very longtimes.[Transcriber's note: Arcs emit ultraviolet rays.]Protector, Comb.A lightning arrester, q. v., comprising two toothed plates nearlytouching each other.Protector, Electric.A protective device for guarding the human body against destructive orinjurious electric shocks. In one system, Delany's, the wrists andankles are encircled by conducting bands which by wires running alongthe arms, back and legs are connected. A discharge it is assumedreceived by the hands will thus be short circuited around the body andits vital organs. India rubber gloves and shoe soles have also beensuggested; the gloves are still used to some extent.Pull.A switch for closing a circuit when pulled. It is used instead of a pushbutton, q.v., in exposed situations, as its contacts are betterprotected than those of the ordinary push button.Pump, Geissler.A form of mercurial air pump. It is used for exhausting Geissler tubes,incandescent lamp bulbs and similar purposes.Referring to the cut, A is a reservoir of mercury with flexible tube Cconnected to a tube at its bottom, and raised and lowered by a windlassb, the cord from which passes over a pulley a. When raised the mercurytends to enter the chamber B, through the tube T. An arrangement ofstopcocks surmounts this chamber, which arrangement is shown on a largerscale in the three figures X, Y and Z. To fill the bulb B, the cocks areset in the position Z; n is a two way cock and while it permits theescape of air below, it cuts off the tube, rising vertically from it.This tube, d in the full figure connects with a vessel o, pressure gaugep, and tube c, the latter connecting with the object to be exhausted.The bulb B being filled, the cock m is closed, giving the position Y andthe vessel A is lowered until it is over 30 inches below B.438 STANDARD ELECTRICAL DICTIONARY.This establishes a Torricellian vacuum in B. The cock n is now turned,giving the position X, when air is at once exhausted from the vesselconnected to C. This process is repeated until full exhaustion isobtained. In practice the first exhaustion is often effected by amechanical pump. By closing the cock on the outlet tube c but little airneed ever find its way to the chambers o and B.Fig. 276. GEISSLER AIR PUMP.439 STANDARD ELECTRICAL DICTIONARY.Pumping.In incandescent lamps a periodical recurring change in intensity due tobad running of the dynamos, or in arc lamps to bad feeding of thecarbons.Fig. 277. SPRENGEL AIR PUMP.Pump, Sprengel.A form of mercurial air pump. A simple form is shown in the cut. Mercuryis caused to flow from the funnel A, through c d to a vessel B. A sideconnection x leads to the vessel R to be exhausted. As the mercurypasses x it breaks into short columns, and carries air down betweenthem, in this way exhausting the vessel R. In practice it is morecomplicated. It is said to give a better vacuum than the Sprengel pump,but to be slower in action.440 STANDARD ELECTRICAL DICTIONARY.Pump, Swinburne.A form of mechanical air pump for exhausting incandescent lamp bulbs.Referring to the cut, A is a bulb on the upper part of a tube G; above Aare two other bulbs C and D. From the upper end a tube runs to the bulbE. Through the cock L, and tube F connection is made with a mechanicalair pump. The tube H leads to a drying chamber I, and by the tube Jconnects with the lamp bulbs or other objects to be exhausted. The tubeG enters the bottle B through an airtight stopper, through which asecond tube with stopcock K passes. In use a vacuum is produced by themechanical pumps, exhausting the lamp bulbs to a half inch and drawingup the mercury in G. The bent neck in the bulb E, acts with the bulb asa trap to exclude mercury from F. When the mechanical pumps haveproduced a vacuum equal to one half inch of mercury, the cock L isclosed and K is opened, and air at high pressure enters. This forces themercury up to the vessel D, half filling it. The high pressure is nowremoved and the mercury descends. The valve in D closes it as themercury falls to the level G. Further air from the lamps enters A, andby repetition of the ascent of the mercury, is expelled, through D. Themercury is again lowered, producing a further exhaustion, and theprocess is repeated as often as necessary.Fig. 278. SWINBURNE'S AIR PUMP.Push-Button.A switch for closing a circuit by means of pressure applied to a button.The button is provided with a spring, so that when pushed in andreleased it springs back. Thus the circuit is closed only as long as thebutton is pressed. The electric connection may be made by pressingtogether two flat springs, each connected to one of the wires, or by thestem of the button going between two springs, not in contact, forcingthem a little apart to secure good contact, and thereby bridging overthe space between them.441 STANDARD ELECTRICAL DICTIONARY.Pyro-electricity.A phenomenon by which certain minerals when warmed acquire electricalproperties. (Ganot.) The mineral tourmaline exhibits it strongly. It wasoriginally observed in this mineral which was found to first attract andthen to repel hot ashes.The phenomenon lasts while any change of temperature within certainlimits is taking place. In the case of tourmaline the range is fromabout 10º C. (50º F.) to 150º C. (302º F.) Above or below this range itshows no electrification.The effect of a changing of temperature is to develop poles, onepositive and the other negative. As the temperature rises one end ispositive and the other negative; as the temperature becomes constant thepolarity disappears; as the temperature falls the poles are reversed.If a piece of tourmaline excited by pyro-electricity is broken, itsbroken ends develop new poles exactly like a magnet when broken.The following minerals are pyro-electric: Boracite, topaz, prehnite,zinc silicate, scolezite, axenite. The following compound substances arealso so: Cane sugar, sodium- ammonium racemate and potassium tartrate.The list might be greatly extended.The phenomenon can be illustrated by sifting through a cotton sieve uponthe excited crystal, a mixture of red lead and flowers of sulphur. Bythe friction of the sifting these become oppositely electrified; thesulphur adheres to the positively electrified end, and the red lead tothe negatively electrified end. (See Analogous Pole-Antilogous Pole.)Pyromagnetic Motor.A motor driven by the alternation of attraction and release of anarmature or other moving part, as such part or a section of it isrendered more or less paramagnetic by heat.Thus imagine a cylinder of nickel at the end of a suspension rod, somounted that it can swing like a pendulum. A magnet pole is placed toone side to which it is attracted. A flame is placed so as to heat itwhen in contact with the magnet pole. This destroys its paramagnetismand it swings away from the magnet and out of the flame. It cools,becomes paramagnetic, and as it swings back is reattracted, to be againreleased as it gets hot enough. This constitutes a simple motor.A rotary motor may be made on the same lines. Nickel is particularlyavailable as losing its paramagnetic property easily.442 STANDARD ELECTRICAL DICTIONARY.Various motors have been constructed on this principle, but none haveattained any practical importance. Owing to the low temperature at whichit loses its paramagnetic properties nickel is the best metal forparamagnetic motors.In Edison's motor, between the pole pieces of an electro-magnet acylinder made up of a bundle of nickel tubes is mounted, so as to befree to rotate. A screen is placed so as to close or obstruct the tubesfarthest from the poles. On passing hot air or products of combustion ofa fire or gas flame through the tubes, the unscreened ones are heatedmost and lose their paramagnetism. The screened tubes are then attractedand the armature rotates, bringing other tubes under the screen, whichis stationary. Then the attracted tubes are heated while the otherscool, and a continuous rotation is the result.Fig. 279. EDISON'S PYROMAGNETIC MOTOR.Pyromagnetic Generator.A current generator producing electric energy directly from thermalenergy by pyromagnetism.Edison's pyromagnetic generator has eight electro-magnets, lying oneight radii of a circle, their poles facing inward and their yokesvertical. Only two are shown in the cut. On a horizontal iron disc aremounted eight vertical rolls of corrugated nickel representingarmatures. On each armature a coil of wire, insulated from the nickel byasbestus is wound. The coils are all in series, and have eightconnections with a commutator as in a drum armature. There are two maindivisions to the commutator. Each connects with an insulated collectingring, and the commutator and collecting rings are mounted on a spindlerotated by power. Below the circle of vertical coils is a horizontalscreen, mounted on the spindle and rotating with it.A source of heat, or a coal stove is directly below the machine and itshot products of combustion pass up through the coils, some of which arescreened by the rotating screen. The effect is that the coils aresubjecting to induction owing to the change in permeability of thenickel cores, according as they are heated, or as they cool when thescreen is interposed. The two commutator segments are in constantrelation to the screen, and current is collected therefrom and by thecollecting rings is taken to the outside circuit.443 STANDARD ELECTRICAL DICTIONARY.Pyromagnetism.The development of new magnetic properties or alteration of magneticsensibility in a body by heat. Nickel and iron are much affected asregards their paramagnetic power by rise of temperature.Fig. 280. PYROMAGNETIC GENERATOR.Pyrometer, Siemens' Electric.An instrument for measuring high temperatures by the variations inelectric resistance in a platinum wire exposed to the heat which is tobe measured.