443 STANDARD ELECTRICAL DICTIONARY.Q.Symbol for electric quantity.Quad.(a) A contraction for quadrant, used as the unit of inductance; the henry.(b) A contraction for quadruplex in telegraphy.[Transcriber's note: A modern use of "quad" is a unit of energy equal to1E15 (one quadrillion) BTU, or 1.055E18 joules. Global energyproduction in 2004 was 446 quad.]Quadrant.A length equal to an approximate earth quadrant, equal to 1E9centimeters. It has been used as the name for the unit of inductance,the henry, q. v.Synonym--Standard Quadrant.444 STANDARD ELECTRICAL DICTIONARY.Quadrant, Legal.The accepted length of the quadrant of the earth, 9.978E8 instead of 1E9centimeters; or to 9,978 kilometers instead of 10,000 kilometers.Quadrature.Waves or periodic motions the angle of lag of one of which, withreference to one in advance of it, is 90°, are said to be in quadraturewith each other.[Transcriber's note: If the voltage and current of a power line are inquadrature, the power factor is zero (cos(90°) = 0) and no real poweris delivered to the load.]Qualitative.Involving the determination only of the presence or absence of asubstance or condition, without regard to quantity. Thus a compass heldnear a wire might determine qualitatively whether a current was passingthrough the wire, but would not be sufficient to determine its quantity.(See Quantitative.)Quality of Sound.The distinguishing characteristic of a sound other than its pitch; thetimbre.It is due to the presence with the main or fundamental sound of otherminor sounds called overtones, the fundamental note prevailing and theother ones being superimposed upon it. The human voice is very rich inovertones; the telephone reproduces these, thus giving the personalpeculiarities of every voice.Synonym--Timbre.Quantitative.Involving the determination of quantities. Thus a simple test wouldindicate that a current was passing through a wire. This would be aqualitative test. If by proper apparatus the exact intensity of thecurrent was determined, it would be a quantitative determination. (SeeQualitative.)Quantity.This term is used to express arrangements of electrical connections forgiving the largest quantity of current, as a quantity armature, meaningone wound for low resistance.A battery is connected in quantity when the cells are all in parallel.It is the arrangement giving the largest current through a very smallexternal resistance.The term is now virtually obsolete (Daniell); "in surface," "inparallel," or "in multiple arc" is used.Quantity, Electric.Electricity may be measured as if it were a compressible gas, bydetermining the potential it produces when stored in a definedrecipient. In this way the conception of a species of quantity isreached. It is also measured as the quantity of current passed by aconductor.Thus a body whose surface is more or less highly charged withelectricity, is said to hold a greater or less quantity of electricity.It may be defined in electrostatic or electro-magnetic terms. (SeeQuantity, Electrostatic--Quantity, Electro-magnetic.)445 STANDARD ELECTRICAL DICTIONARY.Quantity.Electro-magnetic. Quantity is determined electro-magnetically by themeasurement of current intensity for a second of time: its dimensionsare therefore given by multiplying intensity or current strength bytime. The dimensions of intensity are( (M^.5) * (L^.5) ) / Ttherefore the dimensions of electro-magnetic quantity are( ( (M^.5) * (L^.5) ) / T ) * T = ( (M^.5) * (L^.5) )Quantity, Electro-magnetic, Practical Unit of.The quantity of electricity passed by a unit current in unit time; thequantity passed by one ampere in one second; the coulomb.It is equal to 3E9 electrostatic absolute units of quantity and to 0.1of the electro- magnetic absolute unit of quantity.One coulomb is represented by the deposit of.00111815 gram, or .017253 grain of silver,.00032959 gram, or .005804 grain of copper,.0003392 gram, or .005232 grain of zinc.If water is decomposed by a current each coulomb is represented by thecubic centimeters of the mixed gases (hydrogen and oxygen) given by thefollowing formula.( 0.1738 * 76 * (273 + Cº ) ) / ( h * 273 )in which Cº is the temperature of the mixed gases in degree centigradeand h is thepressure in centimeters of mercury column; or by( 0.01058 * 30 (491 + Fº - 32) ) / (h * 491 )for degrees Fahrenheit and inches of barometer.[Transcriber's note: 6.24150962915265E18 electrons is one coulomb.]Quantity, Electrostatic.Quantity is determined electro-statically by the repulsion a charge ofgiven quantity exercises upon an identical charge at a known distance.The force evidently varies with the product of the two quantities, andby the law of radiant forces also inversely with the square of thedistance. The dimensions given by these considerations is Q * Q/(L*L).This is the force of repulsion. The dimensions of a force are(M * L) /(T^2). Equating these two expressions we have:(Q^2)/(L^2) = (M*L)/(T^2)orQ = ((M^.5)*(L^1.5)) / Twhich are the dimensions of electrostatic quantity.Quantity, Meter.An electric meter for determining the quantity of electricity whichpasses through it, expressible in coulombs or ampere hours. Allcommercial meters are quantity meters.446 STANDARD ELECTRICAL DICTIONARY.Quartz.A mineral, silica, SiO2. It has recently been used by C. V. Boys andsince by others in the making of filaments for torsion suspensions. Themineral is melted, while attached to an arrow or other projectile. It istouched to another piece of quartz or some substance to which it adheresand the arrow is fired off from the bow. A very fine filament ofsurpassingly good qualities for galvanometer suspension filaments isproduced.As a dielectric it is remarkable in possessing but one-ninth theresidual capacity of glass.Quicking.The amalgamating of a surface of a metallic object before silverplating. It secures better adhesion of the deposit. It is executed bydipping the article into a solution of a salt of mercury. A solution ofmercuric nitrate 1 part, in water 100 parts, both by weight, is used.
446 STANDARD ELECTRICAL DICTIONARY.R.(a) Abbreviation and symbol for Reamur, as 10º R., meaning 10º by theReamur thermometer. (See Reamur Scale.)(b) Symbol for resistance, as in the expression of Ohm's Law C=E/R.(rho, Greek r) Symbol for specific resistance.Racing of Motors.The rapid acceleration of speed of a motor when the load upon it isremoved. It is quickly checked by counter-electro-motive force. (SeeMotor, Electric.)Radian.The angle whose arc is equal in length to the radius; the unit angle.Radiant Energy.Energy, generally existing in the luminiferous ether, kinetic andexercised in wave transmission, and rendered sensible by conversion ofits energy into some other form of energy, such as thermal energy.If the ether waves are sufficiently short and not too short, theydirectly affect the optic nerve and are known as light waves; they maybe so short as to be inappreciable by the eye, yet possess the power ofdetermining chemical change, when they are known as actinic waves; theymay be also so long as to be inappreciable by the eye, when they may beheat-producing waves, or obscure waves.Other forms of energy may be radiant, as sound energy dispersed by theair, and gravitational energy, whose connection with the ether has notyet been demonstrated.Radiation.The traveling or motion of ether waves through space.[Transcriber's note: The modern term corresponding to this definition isphotons. The modern concept of radiation also includes particles--neutrons, protons, alpha (helium) and beta (electrons) rays and otherexotic items.]Radicals.A portion of a molecule, possessing a free bond and hence free tocombine directly. A radical never can exist alone, but is onlyhypothetical. An atom is a simple radical, an unsaturated group of atomsis a compound radical.447 STANDARD ELECTRICAL DICTIONARY.Radiometer.An instrument consisting of four vanes poised on an axis so as to befree to rotate, and contained in a sealed glass vessel almost perfectlyexhausted. The vanes of mica are blackened on one side.On exposure to light or a source of heat (ether waves) the vanes rotate.The rotation is due to the beating back and forth of air molecules fromthe surface of the vanes to the inner surface of the glass globe.Radiometer, Electric.A radiometer in which the motion of the molecules of air necessary forrotation of the vane is produced by electrification and not by heating.Radio-micrometer.An instrument for detecting radiant energy of heat or light form. Itconsists of a minute thermopile with its terminals connected by a wire,the whole suspended between the poles of a magnet. A minute quantity ofheat produces a current in the thermopile circuit, which, reacted on bythe field, produces a deflection. A convex mirror reflecting light isattached so as to move with the thermopile. The instrument is ofextraordinary sensitiveness. It responds to .5E-6 of a degree Centigradeor about 1E-6 degree Fahrenheit.Radiophony.The production of sound by intermittent action of a beam of light upon abody. With possibly a few exceptions all matter may produce sound byradiophouy.Range Finder.An apparatus for use on shipboard to determine the distance of anothership or object. It is designed for ships of war, to give the range offire, so as to set the guns at the proper elevation. The generalprinciple involved is the use of the length of the ship if possible, ifnot of its width, as a base line. Two telescopes are trained upon theobject and kept trained continuously thereon. The following describesthe Fiske range finder.The range finder comprises two fairly powerful telescopes, each mountedon a standard, which can be rotated round a vertical axis, correspondingwith the center of the large disc shown in the engraving. One-half ofthe edge of this disc is graduated to 900 on either side of a zeropoint, and below the graduation is fixed a length of platinum silverwire. This wire only extends to a distance of 81.10 on either side ofzero, and is intended to form two arms of a Wheatstone bridge. Thesliding contact is carried by the same arm as the telescope standards,so that it moves with the telescope. The two instruments are mounted ata known distance apart on the ship, as shown diagrammatically in thecut. Here A and B are the centers of the two discs, C and D the armscarrying the telescopes, and E and F the platinum silver wires. Supposethe object is at T, such that A B T is a right angle, thenAT=AB/sin(ATB).448 STANDARD ELECTRICAL DICTIONARY.If the two sectors are coupled up as shown, with a battery, h, and agalvanometer, by the wires, a b and c d, then since the arm, e, on beingaligned on the object takes the position c1 while d remains at zero, theWheatstone bridge formed by these segments and their connections will beout of balance, and a current will flow through the galvanometer, whichmay be so graduated as to give the range by direct reading, since thecurrent through it will increase with the angle A T B.Fig. 281. RANGE FINDER.In general, however, the angle A B T will not be a right angle, but someother angle. In this case AT = AB / sin(A T B) * sin( A B T), and henceit will only be necessary to multiply the range reading on thegalvanometer by the sine of the angle A B T, which can be read directlyby the observer at B. This multiplication is not difficult, but bysuitably arranging his electrical appliances Lieutenant Fiske hassucceeded in getting rid of it, so that the reading of the galvanometeralways gives the range by direct reading, no matter what the angle at Bmay be. To explain this, consider the two telescopes shown in the cut inthe positions C and D; the whole current then has a certain resistance.449 STANDARD ELECTRICAL DICTIONARY.Next suppose them, still remaining parallel, in the positions C1 and D1.The total resistance of the circuit is now less than before, and henceif C1, one of the telescopes, is moved out of parallel to the other,through a certain angle, the current through the galvanometer will begreater than if it were moved through an equal angle out of a parallelwhen the telescopes were in the positions C and D. The range indicatedis, therefore, decreased, and by properly proportioning the variousparts it is found that the range can always be read direct from thegalvanometer, or in other words the multiplication of A B/sin( A T B )by sin( A B T ) is to all intents and purposes performed automatically.There is, it is true, a slight theoretical error; but by using a smallstorage battery and making the contents carefully it is said to beinappreciable. Each telescope is fitted with a telephone receiver andtransmitter, so that both observers can without difficulty decide onwhat point to align their telescopes. It will be seen that it isnecessary that the lines of sight of two telescopes should be parallelwhen the galvanometer indicates no current. It has been proposed toaccomplish this by sighting both telescopes on a star near the horizon,which being practically an infinite distance away insures theparallelism of the lines of sight.Rate Governor.An apparatus for securing a fixed rate of vibration of a vibrating reed.It is applied in simultaneous telegraphy and telephoning over one wire.The principle is that of the regular make and break mechanism, with thefeature that the contact is maintained during exactly one-half of theswing of the reed. The contact exists during the farthest half of theswing of the reed away from the attracting pole.Fig. 282. LANGDON DAVIRS' RATE GOVERNOR.In the left hand figure of the cut, K is the key for closing thecircuit. A is the base for attachment of the reed. V is thecontact-spring limited in its play to the right by the screw S. C is theactuating magnet. By tracing the movements of the reed, shown on anexaggerated scale in the three right hand figures, it will be seen thatthe reed is in electric contact with the spring during about one-halfits movement. The time of this connection is adjustable by the screw S.Synonym--Langdon Davies' Rate Governor or Phonophone.450 STANDARD ELECTRICAL DICTIONARY.Ray, Electric. Raia torpedo.The torpedo, a fish having the same power of giving electric shocks asthat possessed by the electric eel, q. v. (See also Animal Electricity.)Fig. 283. TORPEDO OR ELECTRIC RAYReaction of Dynamo, Field and Armature.A principle of the dynamo current generator, discovered by Soren Hjorthof Denmark.When the armature is first rotated it moves in a field due to theresidual magnetism of the field magnet core. This field is very weak,and a slight current only is produced. This passing in part or in wholethrough the field magnet cores slightly strengthens the field, whoseincreased strength reacts on the armature increasing its current, whichagain strengthens the field. In this way the current very soon reachesits full strength as due to its speed of rotation.The operation is sometimes termed building up.Sometimes, when there is but a trace of residual magnetism, it is veryhard to start a dynamo.Reading Telescope.A telescope for reading the deflections of a reflecting galvanometer.A long horizontal scale is mounted at a distance from the galvanometerand directly below or above the centre of the scale a telescope ismounted. The telescope is so directed that the mirror of thegalvanometer is in its field of view, and the relative positions ofmirror, scale and telescope are such that the image of the scale in thegalvanometer mirror is seen by the observer looking through thetelescope.Under these conditions it is obvious that the graduation of the scalereflected by the mirror corresponds to the deflection of thegalvanometer needle.The scale may be straight or curved, with the galvanometer in the lattercase, at its centre of curvature.Reamur Scale.A thermometer scale in use in some countries of Continental Europe. Thetemperature of melting ice is 0°; the temperature of condensing steamis 80°; the degrees are all equal in length. For conversion tocentigrade degrees multiply degrees Reamur by 5/4. For conversion toFahrenheit degrees multiply by 9/4 and add 32 if above 0° R., and ifbelow subtract 32. Its symbol is R., as 10° R.451 STANDARD ELECTRICAL DICTIONARY.Recalescence.A phenomenon occurring during the cooling of a mass of steel, when itsuddenly emits heat and grows more luminous for an instant. It is aphase of latent heat, and marks apparently the transition from anon-magnetizable to a magnetiz able condition.Receiver.In telephony and telegraphy, an instrument for receiving a message asdistinguished from one used for sending or transmitting one.Thus the Bell telephone applied to the ear is a receiver, while themicrophone which is spoken into or against is the transmitter.Receiver, Harmonic.A receiver including an electro-magnet whose armature is an elasticsteel reed, vibrating to a particular note. Such a reed responds to aseries of impulses succeeding each other with the exact frequency of itsown natural vibrations, and does not respond to any other rapid seriesof impulses. (See Telegraph Harmonic.)Reciprocal.The reciprocal of a number is the quotient obtained by dividing one bythe number. Thus the reciprocal of 8 is 1/8.Applied to fractions the above operation is carried out by simplyinverting the fraction. Thus the reciprocal of 3/4 is 4/3 or 1-1/3.Record, Telephone.Attempts have been made to produce a record from the vibrations of atelephone disc, which could be interpreted by phonograph or otherwise.Fig. 284. MORSE RECORDER OR EMBOSSER.452 STANDARD ELECTRICAL DICTIONARY.Recorder, Morse.A telegraphic receiving apparatus for recording on a strip of paper thedots and lines forming Morse characters as received over a telegraphline. Its general features are as follows:A riband or strip of paper is drawn over a roller which is slightlyindented around its centre. A stylus or blunt point carried by avibrating arm nearly touches the paper. The arm normally is motionlessand makes no mark on the paper. An armature is carried by the arm and anelectro-magnet faces the armature. When a current is passed through themagnet the armature is attracted and the stylus is forced against thepaper, depressing it into the groove, thus producing a mark. When thecurrent ceases the stylus is drawn back by a spring.Fig. 285. INKING ROLLER MECHANISM OF MORSE RECORDER.In some instruments a small inking roller takes the place of the stylus,and the roller is smooth. The cut, Fig. 285, shows the plan view of theink-roller mechanism. J is the roller, L is the ink well, Cl is the armby which it is raised or lowered by the electro-magnet, as in theembosser. S S is the frame of the instrument, and B the arbor to whichthe arm carrying the armature is secured, projecting to the right. Aspring is arranged to rub against the edge of the inking roller andremove the ink from it.The paper is fed through the apparatus by clockwork. At the present daysound reading has almost entirely replaced the sight reading of therecorder.Recorder, Siphon.A recording apparatus in which the inked marks are made on a strip ofpaper, the ink being supplied by a siphon terminating in a capillaryorifice.In the cut N S represents the poles of a powerful electro-magnet. Arectangular coil bb of wire is suspended between the coils. A stationaryiron core a intensifies the field. The suspension wire f f 1 has itstension adjusted at h. This wire acts as conductor for the current.453 STANDARD ELECTRICAL DICTIONARY.The current is sent in one or the other direction or is cut off inpractice to produce the desired oscillations of the coil b b. A glasssiphon n l works upon a vertical axis l. One end l is immersed in an inkwell m. Its longer end n touches a riband of paper o o. The thread kattached to one side of the coil pulls the siphon back and forthaccording to the direction of current going through the electro-magnetcores. A spiral spring adjusted by a hand-screw controls the siphon. Inoperation the siphon is drawn back and forth producing a zigzag line.The upward marks represent dots, the downward ones dashes. Thus theTelegraphic Code can be transmitted on it. To cause the ink to issueproperly, electrification by a static machine has been used, when thestylus does not actually touch the paper, but the ink is ejected in aseries of dots.Fig. 286. SIPHON RECORDER.Reducteur for Ammeter.A resistance arranged as a shunt to diminish the total current passingthrough an ammeter. It is analogous to a galvanometer shunt. (SeeMultiplying Power of Shunt.)Reducteur for Voltmeter.A resistance coil connected in series with a Voltmeter to diminish thecurrent passing through it. Its resistance being known in terms of theresistance of the voltmeter it increases the range of the instrument sothat its readings may cover double or more than double their normalrange.Reduction of Ores, Electric.Treatment of ores by the electric furnace (see Furnace, Electric.) Theore mixed with carbon and flux is melted by the combined arc andincandescent effects of the current and the metal separates. In anothertype the metal is brought into a fusible compound which is electrolyzedwhile fused in a crucible. Finally processes in which a solution of asalt of the metal is obtained, from which the metal is obtained byelectrolysis, may be included. Aluminum is the metal to whose extractionthe first described processes are applied.454 STANDARD ELECTRICAL DICTIONARY.Refraction, Electric Double.Double refraction induced in some materials by the action of either anelectrostatic, magnetic or an electro-magnetic field.The intensity or degree of refracting power is proportional to thesquare of the strength of field.Refreshing Action.In electro-therapeutics the restoration of strength or of nerve force bythe use of voltaic alternatives, q. v.Region, Extra-polar.In electro-therapeutics the area or region of the body remote from thetherapeutic electrode.Region, Polar.In electro-therapeutics the area or region of the body near thetherapeutic electrode.Register, Electric.There are various kinds of electric registers, for registering themovements of watchmen and other service. Contact or press buttons may bedistributed through a factory. Each one is connected so that when thecircuit is closed thereby a mark is produced by the depression of apencil upon a sheet or disc of paper by electro-magnetic mechanism. Thepaper is moved by clockwork, and is graduated into hours. For eachpush-button a special mark may be made on the paper. The watchman isrequired to press the button at specified times. This indicates hismovements on the paper, and acts as a time detector to show whether hehas been attending to his duty.Register, Telegraphic.A term often applied to telegraph recorders, instruments for producingon paper the characters of the Morse or other alphabet.Regulation, Constant Current.The regulation of a dynamo so that it shall give a constant currentagainst any resistance in the outer circuits, within practical limits.It is carried out in direct current machines generally by independentregulators embodying a controlling coil with plunger or some equivalentelectro-magnetic device inserted in the main circuit and necessarily oflow resistance. In some regulators the work of moving the regulator isexecuted mechanically, but under electrical control; in others theentire work is done by the current.A typical regulator or governor (Golden's) of the first class comprisestwo driven friction wheels between which is a driving friction wheel,which can engage with one driven wheel only at once. It is brought intoengagement with one or the other by a solenoid and plunger.455 STANDARD ELECTRICAL DICTIONARY.As it touches one wheel it turns it in one direction. This moves asliding contact in one direction so as to increase a resistance. Thiscorresponds to a motion of the plunger in one direction. As the drivingwheel moves in the opposite direction by a reverse action it diminishesthe resistance. Thus the increase and decrease of resistance correspondto opposite movements of the solenoid plunger, and consequently toopposite variations in the current. The whole is so adjusted that thevariations in resistance maintain a constant amperage. The resistance isin the exciting circuit of the dynamo.In Brush's regulator, which is purely mechanical, a series dynamo ismade to give a constant current by introducing across the field magnetsa shunt of variable resistance, whose resistance is changed by anelectro-magnet, whose coils are in circuit with the main current. Carbonresistance discs are used which the electro-magnet by its attraction forits armature, presses with varying intensity. This alters theresistance, decreasing it as the current increases and the reverse. Asthe connection is in shunt this action goes to maintain a constantcurrent.Regulation, Constant Potential.The regulation of constant potential dynamos is executed on the samelines as that of constant current dynamos. If done by a controllingcoil, it must for constant potential regulation be wound with fine wireand connected as a shunt for some part of the machine.Regulation of Dynamos.The regulation of dynamos so that they shall maintain a constantpotential difference in the leads of their circuit for multiple arcsystems or shall deliver a constant current in series systems. Hence twodifferent systems of regulation are required, (a) constant potentialregulation--(b) constant current regulation. The first named is by farthe more important, as it concerns multiple arc lighting, which is thesystem universally used for incandescent lighting.S. P. Thompson thus summarizes the methods of governing or regulatingdynamos. Premising that alteration of the magnetic flux is the almostuniversal way of control, it can be done in two ways; first, by varyingthe excitation or ampere turns of the field, and second by varying thereluctance of the magnetic circuit. The excitation or magnetic flux maybe varied(a) by hand, with the aid of rheostats and commutators in the excitingcircuit;(b) automatically, by governors, taking the place of the hand;(c) by compound windings. The magnetic circuit may have its reluctancecaused to vary in several ways;(d) by moving the pole pieces nearer to or further from the armature;(e) by opening or closing some gap in the magnetic circuit (field-magnetcore);(f) by drawing the armature endways from between the pole pieces;(g) by shunting some of the magnetic lines away from the armature by amagnetic shunt.The latter magnetic circuit methods d, e, f, and g, have never met withmuch success except on small machines or motors. Method e is adopted inthe Edison motor, the yoke being withdrawn or brought nearer the coresof the coils. (See Regulation, Constant Current-Regulation, constantPotential.)456 STANDARD ELECTRICAL DICTIONARY.Reguline. adj.Having the characteristics of a piece of metal, being flexible,adherent, continuous, and coherent. Applied to electrolytic deposits.Relative.Indicating the relation between two or more things without reference toabsolute value of any one of them. Thus one lamp may be of relativelydouble resistance compared to another, but this states nothing of theresistance in ohms of either lamp.Relay.A receiving instrument which moves in accordance with impulses ofcurrents received, and in so moving opens and closes a local circuit,which circuit may include as powerful a battery as required ordesirable, while the relay may be on the other hand so delicate as towork with a very weak current.Fig. 287. RELAY.The typical relay includes an electro-magnet and armature. To the latteran arm is attached and the lower end of the arm works in pivots. As thearmature is attracted the arm swings towards the magnet. When thecurrent is cut off, the armature and arm are drawn back by a spring.When the arm swings towards the magnet its upper end touching a contactscrew closes the local circuit. When it swings back it comes in contactwith a second screw, with insulated point, and opens the circuit as itleaves the first named screw.One terminal connects with the arm through the pivots and frame. Theother connects with the contact screw through the frame carrying it.Synonym--Relay Magnet.457 STANDARD ELECTRICAL DICTIONARY.Relay Bells.Bells connected by relay connection to a main line for acoustictelegraphy. A stroke on one bell indicates a dot and on the other adash. The system is now nearly extinct.Relay, Box-sounding.A relay which is surrounded by or mounted on a resonator or wooden boxof such proportions and size as to reinforce the sound. This enables arelay to act as a sounder, its weak sounds being virtually magnified soas to be audible.Relay Connection.A connection used in telegraphy, including a local battery, with a shortcircuit normally open, but closed by a switch and a sounder or otherappliance. The latter is made very sensitive so as to be worked by afeeble current, and is connected to the main line. A very slight currentcloses the switch and the local battery comes into operation to work asounder, etc. When the current ceases on the main line the switch opensand throws the local battery out of action. The switch is termed arelay, q. v. A long main line may thus produce strong effects at distantstations, the intensity of action depending on the local battery.Fig. 288. RELAY OR LOCAL CIRCUIT.Relay, Differential.A relay containing two coils wound differentially, and of the samenumber of turns and resistance. If two equal currents pass through thecoils they counteract each other and no action takes place. If there isa difference in the currents the relay acts as one coil preponderates.The coils may be wound for uneven currents with different resistance andnumber of turns.Relay, Microphone.A relay connection applied to a telephone circuit. It consists of amicrophone mounted in front of the diaphragm of a telephone receiver. Incircuit with the microphone is a battery and second telephone receiver.The microphone is supposed to intensify the sounds of the firsttelephone.458 STANDARD ELECTRICAL DICTIONARY.Relay, Polarized.A relay whose armature is of steel, and polarized or permanentlymagnetized, or in which a permanent magnet is used as the basis for theelectro-magnets. In the relay shown in the cut the coils shown aremounted on cores carried on the end of a powerful bent permanent magnet.Thus when no current passes their upper poles are both of the same sign,and the horizontally vibrating tongue is held by the magnetic attractionagainst one or the other pole piece. If a current is sent through theelectro-magnet it gives opposite polarity to the two polar extensions.As the end of the vibrating tongue is of polarity determined by thepermanent magnet it is attracted to one pole and repelled from theother. On cessation of current it remains attached by the permanentmagnetism. If now a current is sent in the opposite direction the twopoles again acquire opposite polarity, the reverse of the former, andthe tongue flies across to the opposite side. On cessation of current itremains attached as before by the permanent magnetism.In its movements to and fro the relay tongue opens and closes a contact,so as to work a sounder or other apparatus. The polarized relay is ofhigh sensibility, and requires little or no change of adjustment.Fig. 288. POLARIZED RELAYReluctance.In a magnetic circuit or portion thereof, the resistance offered to theflow of lines of force. The magnetic circuit as has already been statedis treated like an electric circuit, and in it reluctance occupies theplace of resistance in the electric circuit. It is the reciprocal ofpermeance. S. P. Thompson expresses the law thus:Total number of magnetic lines = (magneto-motive force) / (magneticreluctance)Synonyms--Magnetic Reluctance-Magnetic Resistance.Reluctance, Unit of.The reluctance of a circuit through which unit magnetizing power(magneto-motive force) can produce a unit of induction or one line offorce. This value is very high; the reluctance of ordinary magneticcircuits ranges from 1E-5 to 1E-8 unit of reluctance.Reluctivity.Specific reluctance; the reluctance of a cube of material whose edgemeasures one centimeter in length. It is a quality bearing the samerelation to reluctance that permeability does to permeance.It is defined as the reciprocal of magnetic permeability. (Kenelly.) Ifplotted as a curve for different values of the magnetizing force it isfound to be nearly a straight line, a linear function of the magnetizingforce, H with the equation a + b H. Reluctivity is the property of asubstance; reluctance is the property of a circuit.459 STANDARD ELECTRICAL DICTIONARY.Remanence.The residual magnetism left after magnetic induction, expressed in linesof force per square centimeter.Repeater.In telegraphy an instrument for repeating the signals through a secondline. It is virtually a relay which is operated by the sender, and whichin turn operates the rest of the main line, being situated itself atabout the middle point of the distance covered. In the simpler forms ofrepeater two relays are used, one for transmission in one direction theother for transmission in the other. An attendant switches one or theother in as required.Thus a common relay is virtually a repeater for its local circuit. Ifsuch a relay is placed half way down a line, and if the line beyond itis connected as its local, it becomes a repeater.Some forms of repeaters are automatic, and repeat both ways without theneed of an attendant.It is the practice to somewhat prolong the signals sent through arepeater.Replenisher, Sir William Thomson's.A static accumulating influence machine contained in Thomson's quadrantelectrometer and used to change the quadrants. The cut shows thehorizontal section and construction of the apparatus.It contains two gilt brass inductors A B, and two eccentric sectors orcarriers, C, D, which are mounted on an ebonite spindle, which is spunaround by the fingers. The springs s s1 connect each with its inductor;the springs S S1 connect only each other, and touch the sectors as theyturn around.One of the inductors may be always assumed to be of slightly higherpotential than that of the other one. When the carriers are in contactwith the springs S S1 they are each charged by induction withelectricity opposite in sign to that of the nearest quadrant. As theyleave the springs S S1 in their rotation, they next touch the springs ss1, but of the recently opposite inductor. They share each a portion ofits charge with the inductors building up their charges. The action isrepeated over and over again as they rotate.
Fig. 289. DIAGRAM OF THOMSON'S REPLENISHER.
Fig. 290. THOMSON'S REPLENISHER.460 STANDARD ELECTRICAL DICTIONARY.Reservoir, Common.A term applied to the earth, because all electrified bodies dischargeinto it if connected thereto.Residual Atmosphere.The air left in a receiver after exhaustion by an air pump. Thequantity, where good air pumps are used, is very minute.Residue, Electric.The residual charge of a condenser. (See Charge, Residual.)Resin.(a) The product obtained by non-destructive distillation of the juice ofthe pitch pine. It is the solid residue left after the turpentine hasbeen evaporated or distilled. It is a mixture of abietic acid C44 H64 O5and pinic acid C20 H30 O2. It is an insulator; its specific inductivecapacity is 2.55. (Baltzmann.)Synonyms--Colophony--Rosin.(b) The name is also generally applied to similar substances obtainedfrom the sap of other trees; thus shellac is a resin. The resins are afamily of vegetable products; the solid portions of the sap of certaintrees. Common resin, lac, dragons blood, are examples. They are alldielectrics and sources of resinous or negative electricity when rubbedwith cotton, flannel, or silk. (See Electrostatic Series.)461 STANDARD ELECTRICAL DICTIONARY.Resinous Electricity.Negative electricity; the electricity produced upon the surface of aresinous body by rubbing it; such a body is shellac or sealing wax;flannel and other substances may be used as the rubbing material. (SeeElectrostatic Series.)Resistance.(a) The quality of an electric conductor, in virtue of which it opposesthe passage of an electric current, causing the disappearance ofelectro-motive force if a current passes through it, and convertingelectric energy into heat energy in the passage of a current through it.If a current passes through a conductor of uniform resistance there is auniform fall of potential all along its length. If of uneven resistancethe fall in potential varies with the resistance. (See Potential, Fallof.)The fall of potential is thus expressed by Daniell. "In a conductor, saya wire, along which a current is steadily and uniformly passing, thereis no internal accumulation of electricity, no density of internaldistribution; there is, on the other hand, an unequally distributedcharge of electricity on the surface of the wire, which results in apotential diminishing within the wire from one end of the wire to theother."Resistance varies inversely with the cross section of a cylindrical orprismatic conductor, in general with the average cross-section of anyconductor, and in the same sense directly with its true or average orvirtual length. It varies for different substances, and for differentconditions as of temperature and pressure for the same substance. A riseof temperature in metals increases the resistance, in some badconductors a rise of temperature decreases the resistance.462 STANDARD ELECTRICAL DICTIONARY.Approximately, with the exception of iron and mercury, the resistance ofa metallic conductor varies with the absolute temperature. This is veryroughly approximate.Except for resistance energy would not be expended in maintaining acurrent through a circuit. The resistance of a conductor may be supposedto have its seat and cause in the jumps from molecule to molecule, whichthe current has to take in going through it. If so a current confined toa molecule would, if once started, persist because there would be noresistance in a molecule. Hence on this theory the Ampérian currents(see Magnetism, Ampere's Theory of) would require no energy for theirmaintenance and Ampére's theory would become a possible truth.When metals melt their resistance suddenly increases.Light rays falling on some substances, notably selenium, q. v., vary theresistance.Longitudinal stretching of a conductor decreases it, it increases withlongitudinal compression, and increases in iron and diminishes in tinand zinc when a transverse stress tends to widen the conductor.(b) The term resistance is used to express any object or conductor usedin circuit to develop resistance.[Transcriber's note: At room temperatures, the thermal motion of ions inthe conductor's crystal lattice scatters the electrons of the current.Imperfections of the lattice contribute slightly. At low temperaturessuperconductivity (zero resistance) can occur because an energy gapbetween the electrons and the crystal lattice prevents any interaction.At the time of this book, none of this was known. "Jumps from moleculeto molecule" is a good guess.]Resistance, Apparent.Impedance; the virtual resistance of a circuit including the spuriousresistance due to counter-electromotive force. It may be made up of trueresistance and partly of an inductive reaction, as it represents the netfactor, the entire obstruction to the passage of a current, and notmerely a superadded resistance or counter-electro-motive force.Synonym--Impedance.[Transcriber's note: Impedance can also have a component due tocapacitance.]Resistance, Asymmetrical.Resistance which varies in amount in different directions through aconductor. It implies a compound or composite conductor such as thehuman system. The presence of counter-electro-motive force in differentparts of a conductor may bring about asymmetrical resistance.Resistance, B. A. Unit of.The British Association Ohm. (See Ohm, B. A.)463 STANDARD ELECTRICAL DICTIONARY.Resistance Box.A box filled with resistance coils. The coils are connected in series sothat a circuit including any given number has their aggregate resistanceadded to its own. The terminals of consecutive coils are connected toshort blocks of brass which are secured to the top of the box, lyingflatwise upon it, nearly but not quite in contact with each other. Plugsof brass are supplied which can go in between pairs of blocks, whichhave a pair of grooves reamed out to receive them. Such plugs shortcircuit the coil below them when in position. The cut shows how suchcoils are connected and the use of plugs to short circuit them. Thediagram shows the top of a Wheatstone bridge, q. v., resistance box withconnections for determining resistances.Fig. 291. RESISTANCE BOX.Resistance Box, Sliding.A resistance box whose coils are set in a circle. Two metal arms withhandles are pivoted at the centre of the circle and by moving themaround they make and break contacts so as to throw the coils in and outof circuit. The object is to permit an operator to adjust resistancewithout looking at the box--an essential in duplex telegraphy.Resistance, Breguet Unit of.The same in origin as the Digney Unit. (See Resistance, Digney Unit of.)It is equal to 9.652 Legal Ohms.Resistance, Carbon.A resistance, a substitute for a resistance coil; it is made of carbon,and is of various construction. In the Brush dynamo regulator a set offour vertical piles of plates of retort carbon, q. v., is used as aresistance, whose resistance is made to vary by changing the pressure.This pressure automatically increases as the current strength increases,thus reducing the resistance.464 STANDARD ELECTRICAL DICTIONARY.Resistance Coil, Standard.A standard or resistance issued by the Electric Standard Committee ofGreat Britain. The cut shows the standard ohm. It is formed either ofGerman silver, or of an alloy of silver, 66.6 per cent. and platinum,33.4 per cent. The wire is insulated and doubled before winding asdescribed before. (See Coil, Resistance.) The two ends of the wire aresoldered, each one to a heavy copper wire or rod r. The whole coil isenclosed in a brass case, and is enclosed with paraffine melted in at A.A place for a thermometer is provided at t. By immersing the lower partof the case B in water of different degrees of heat any desiredtemperature can be attained.Fig. 292. STANDARD OHM COIL.Resistance, Combined.The actual resistance of several parallel conductors starting from thesame point and ending at the same point. If the individual resistance bea b c d .. and the combined resistance be x then we havex = 1 / (( 1/a) + (1/b) + (1/c) + (1/d) + …)Synonym--Joint Resistance.Resistance, Critical.In a series wound dynamo the resistance of the outer circuit above whichthe machine will refuse to excite itself.Resistance, Dielectric.The mechanical resistance of a dielectric to the tendency to perforationor to the strains due to electrification. This is a phase of mechanicalresistance, and is distinct from the electrical or ohmic resistance ofthe same substance.Resistance, Digney Unit of.The resistance of an iron wire, 1 kilometer long, 4 millimetersdiameter, temperature unknown.It is equal to 9.163 legal ohms.Resistance, Electrolytic.The resistance of an electrolyte to the passage of a current decomposingit. It is almost entirely due to electrolysis and is added to bycounter- electro-motive force, yet it is not treated specifically assuch, but as an actual resistance. When a current of a circuit of toolow voltage to decompose an electrolyte is caused by way of immersedterminals to pass through an electrolyte the resistance appears veryhigh and sometimes almost infinite. If the voltage is increased untilthe electrolyte is decomposed the resistance suddenly drops, and whatshould be termed electrolytic resistance, far lower than the trueresistance, appears.465 STANDARD ELECTRICAL DICTIONARY.Resistance, English Absolute or Foot-Second Unit of.A unit based on the foot and second. It is equal to (( foot / second ) *1E7) , being based on these dimensions.It is equal to 0.30140 legal ohm.Resistance, Equivalent.A resistance equivalent to other resistances, which may includecounter-electro-motive force.Resistance, Essential.The resistance of the generator in an electric circuit; the same asinternal resistance.Resistance, External.In an electric circuit the resistance of the circuit outside of thegenerator, or battery.Synonym--Non-essential Resistance.Fig. 293. RESISTANCE FRAME.Resistance Frame.An open frame filled with resistance coils of iron, or German silverwire. It is used as a resistance for dynamos and the larger or workingclass of plant. The coils are sometimes connected so that by a switchmoving over a row of studs one or more can be thrown into seriesaccording to the stud the switch is in contact with.Resistance, German Mile Unit of.The resistance of 8,238 yards of iron wire 1/6 inch in diameter. It isequal to 56.81 legal ohms.466 STANDARD ELECTRICAL DICTIONARY.Resistance, Hittorf's.A high resistance, often a megohm, composed of Hittorf's solution, q. v.It is contained in a vertical glass tube near whose upper and lower endsare electrodes of metallic cadmium attached to platinum wires. Thecadmium is melted in glass tubes, the platinum wire is inserted into themelted metal and the tube is broken after all is solid. The resistanceshould show no polarization current.Fig. 294. HITTORF'S RESISTANCEResistance, Inductive.A resistance in which self-induction is present; such as a coil ofinsulated wire wound around an iron core.Resistance, Insulation.The resistance of the insulation of an insulated conductor. It is statedin ohms per mile. It is determined by immersing a section of the line inwater and measuring the resistance between its conductor and the water.The section must be of known length, and its ends must both be above theliquid.Resistance, Internal.The resistance of a battery, or generator in an electric circuit asdistinguished from the resistance of the rest of the circuit, or theexternal resistance.Synonym--Essential Resistance.Resistance, Jacobi's Unit of.The resistance of a certain copper wire 25 feet long and weighing 345grains.It is equal to 0.6296 legal ohm.Resistance, Matthiessen's Meter-gram Standard.The resistance of a pure hard drawn copper wire of such diameter thatone meter of it weighs one gram. It is equal to .1434 Legal Ohms at 0ºC. (32º F.)Resistance, Matthiessen's Unit of.The resistance of a standard mile of pure annealed copper wire 1/16 inchdiameter, at a temperature of 15.5º C. (60º F.).It is equal to 13.44 legal ohms.467 STANDARD ELECTRICAL DICTIONARY.Resistance, Meter-millimeter Unit of.The resistance of a wire of copper one meter long and one squaremillimeter in section. It is equal to .02057 ohms at 0º C. (32º F.) Theterm may also be applied to the resistance of similar sized wire ofother metals.Resistance, Mil-foot Unit of.The resistance of a foot of copper wire one-thousandth of an inch indiameter. It is equal to 9.831 ohms at 0º C. (32º F.) The term may alsobe applied to the resistance of similar sized wire of other metals.Resistance, Non-essential.The resistance of the portion of an electric circuit not within thegenerator; the same as external resistance.Synonym--External Resistance.Resistance, Non-inductive.A resistance with comparatively little or negligible self-induction.Resistance of Human Body.The resistance of the human body is largely a matter of perfection ofthe contacts between its surface and the electrodes. It has beenasserted that it is affected by disease. From 350 to 8,000 ohms havebeen determined as resistances, but so much depends on the contacts thatlittle value attaches to the results.Resistance, Ohmic.True resistance measured in ohms as distinguished fromcounter-electro-motive force, q. v. The latter is called often spuriousresistance.Synonym--True Resistance.[Transcriber's note: "True" vs. "spurious" are interesting terms,considering that today we define impedance as a combination of "real"resistance and "imaginary" capacitive and inductive reactance.]Resistance, Reduced.The resistance of a conductor reduced to ohms, or to equivalent lengthsof a column of mercury, 1 square millimeter in cross area.Resistance, Siemen's Unit of.The resistance of a column of mercury 1 meter long and 1 squaremillimeter cross-sectional area at 0º C. (32º F.)It is equal to .9431 legal ohm.Resistance, Specific.The relative resistance of a substance. It is expressed as the actualresistance of a cube of the substance which is one centimeter on eachedge. For metals it is usually expressed in microhms, for liquids inohms.The resistances of a specified length of wire of specified diameter ofdifferent substances is often given, and is really a particular way ofstating specific resistances.Synonym--Specific Conduction Resistance.Resistance, Spurious.The counter-electro-motive force, q. v., operating to prevent a currentbeing produced of what should be its full strength were the trueresistance and actuating electro-motive force only concerned. Suchcounter-electro-motive force may be treated as a spurious resistance andsuch a value in ohms assigned to it as would correspond to its propereffect.468 STANDARD ELECTRICAL DICTIONARY.In its effect on opposing a current and in resisting its formation itdiffers from true resistance. The latter in diminishing current strengthabsorbs energy and develops heat; spurious resistance opposes anddiminishes a current without absorption of energy or production of heat.[Transcriber's note: "Spurious resistance" is now called reactance,consisting of capacitive reactance and inductive reactance. Thecombination of reactance and (Ohmic/true) resistance is calledimpedance. The calculation of impedance requires complex algebra, notjust real values used in DC circuit analysis.]Resistance, Steadying.When arc lamps are connected in parallel or multiple arc a smallresistance coil is sometimes placed in series with each lamp forsteadying purposes. It reduces the percentage of variation of resistancein each lamp, which may be caused by a change in the position of thecarbons.Resistance, Swiss Unit of.A unit constructed by the "Administration Suisse," based on the samedata as the Breguet and the Digney Units. (See Resistance, Digney Unitof)It is equal to 10.30 legal ohms.Resistance, Thomson's Unit of.A unit of resistance based on the foot and second.It is equal to 0.3166 legal ohm.Resistance, Unit.Unit resistance is that of a conductor in which unit current is producedby unit electro-motive force.Resistance, Varley's Unit of.The resistance of a standard mile of a special copper wire 1/16 inchdiameter.It is equal to 25.33 ohms.Resistance, Weber's Absolute Unit.A metric system unit; (meter / second) * 1E7It is equal to 0.9089 legal ohm.Resonance, Electric.A set of phenomena known as the Hertz experiments are grouped under thistitle, which phenomena are incidents of and depend on the propagation ofelectric waves through wires or current conductors, as well as throughthe ether. Ordinarily a wire is only a seat of current, and is in itsnature inconsistent with wave propagation through its mass. Such wavesare virtually confined to the exterior of the wire. The point is thatthe current-producing force is supposed to enter the wire at all pointsfrom without, the current not being produced by an end-push. Hence inrapidly recurring waves which are produced by a rapidly pulsatory oralternating current, no time is afforded for the current-producingforce, in this case the wave-producing force, to penetrate into thesubstance of the wire. In one of his experiments Dr. Hertz surrounded awire by a glass tube chemically silvered. The coating was so thin as tobe translucent. Through this metallic layer a current could be inducedin the wire in its interior. Any mechanical layer of metal took up theinduction itself, and protected the central wire. This gave a clue tothe thickness of metal penetrated by the rapid induced waves used by Dr.Hertz.469 STANDARD ELECTRICAL DICTIONARY.Fig. 295. ELECTRICAL RESONANCE EXCITER.The method used for the production of rapid oscillations is thefollowing. To the terminals of an induction coil two metal spheres AA1are connected as shown. This apparatus is termed the exciter; in itsdischarge a series of isochronous discharges takes place, alternating indirection. The period of duration T of a single one is given by theformula T= 2* PI * squareRoot( LC ), in which C is the capacity and Lis the self-induction. The spheres may be 30 centimeters (11.8 inches)in diameter, connected each to conductors 0.5 centimeter (.2 inch) indiameter and 40 centimeters (15.7 inches) long each. For the length ofan undulation the formula gives for this apparatus 4.8 meters (15.75feet) as the length of a wave, assuming for them the velocity ofpropagation equal to that of light. The exciter may have 10,000 timesthe rate of oscillation possessed by the plain induction coil.When this apparatus is worked it produces induced waves in everyneighboring conductor. The resonance effects appear in the size of thespark induced. Thus a wire bent into a circle with its ends nearlytouching will give a spark, but if made of proper electrostaticcapacity, corresponding with the particular waves employed, the sparkwill be very much larger. The ring, with its spark gap is termed aresonator. It is used as an explorer to trace the waves.Waves thus produced are transmitted by stone walls and nonconductors ingeneral. A plate of zinc reflects part and transmits part. The reflectedwaves can be traced by the resonator, their angle of reflection beingequal to their angle of incidence. They can be received by one parabolicreflector, reflected to another and brought to a focus. They can bereflected so as to produce interference or loops and nodes, and theloops and nodes can be traced by the resonator. By a prism of asphaltthey are refracted exactly like light.From all this it is concluded that an additional proof is furnished ofthe identity of light and electro-magnetic waves, and a very strongexperimental proof of Maxwell's theory of light is furnished.Synonym--Hertz's Experiments.470 STANDARD ELECTRICAL DICTIONARY.Fig. 296. ELECTRICAL RESONATOR.Resonator, Electric.A small open electric circuit, with ends nearly touching. When exposedto electric resonance, or to a sympathetic electric oscillatorydischarge, a spark passes from across the gap. The production of thisspark is altogether a matter of the inductance of the resonator. Thesimplest form is a circle of copper wire with its ends nearly touching.The length of the gap is adjustable by bending. A screw adjustment mayalso be provided. Another form is shown in the cut, Fig. 296. Heresheets of tinfoil are used to regulate the electrostatic capacity, whileat m is shown the finger piece for regulating the size of the spark gapa.Synonym--Spark Micrometer.Resultant.The line indicating the result of the application of two or more forcesto a point. Its direction and length give the elements of direction andintensity. (See Forces, Resolution of Forces, Composition ofComponents.)Resultant Polarity.The magnetic polarity imparted to a mass of iron acted on by two or moreseparate inducing forces or currents. It appears in dynamos and motors.The final polarity is the resultant of the inducing effect of the fieldmagnet poles and of the windings.Retardation.In telegraphy a retardation of the rate of transmission of signals. Itis due to several causes.(a) The self-induction of the circuit, especially if it includes manyelectro-magnets, produces extra currents (see Currents, Extra.) Theseare opposed to the main current on closing it and hence retard theaction. They are in the same direction on opening it and hence againretard the action.(b) Every line has a certain static capacity. This is affected by theproximity of the lines to the earth. For each signal electricity has tobe charged upon the line until the line is charged to its end with acertain proportion of the initial density. This charging takes time andhence introduces retardation.(c) The cores of the electro-magnets of the relays or sounders are notinstantly magnetized and demagnetized. This magnetic lag, q. v.,introduces retardation.471 STANDARD ELECTRICAL DICTIONARY.Retardation of Phase.The fractional lagging behind of waves or alternating currents; bylagging behind a portion of a wave length the corresponding phases, asof full amplitude, are kept back or retarded. The phase of currentintensity may be retarded with reference to the electro-motive force bythe introduction of transformers of high capacity with high resistanceon open secondary circuits.[Transcriber's note: Capacitors are used to correct current phase lag.]Retentivity.Coercitive or coercive force; by virtue of which steel retains itsmagnetism. It is the more modern name, "coercive force" as a term beingrejected by many.Synonyms--Coercive Force--Coercitive Force.Retort Carbon.Carbon deposited in coal gas retorts from decomposition of thehydrocarbons. It is a very hard, pure form, and is of graphiticmodification. Owing to its great hardness it is little used forelectrical purposes, the molded carbons being easier to make. Thedeposition occurs in the regular gas-making process, and is adisadvantage to the working.Return.A line or conductor which is supposed to carry current back to itsstarting point, after it has traversed a line. It may be a wire or thegrounding of the ends of a line [or] may make the earth act as a return,termed ground- or earth-return. The best distinction of a return is toso term the portion of a circuit on which no apparatus is placed.Reversibility.The principal in virtue of which a device for producing a given form ofenergy can absorb the same and do work. The reversibility of the dynamois its quality in virtue of which it can act as a current generator,thereby converting mechanical energy into electric energy, or if acurrent is passed through it, it rotates, doing work, and therebyconverting electric energy into mechanical energy. The knowledge of thisprinciple can be traced back to Jacobi in 1850.Reversible Bridge.A form of Wheatstone's Bridge adapted for reversal of the positions orinterchange of the proportionate arms, v., so that the accuracy of thecoils can be tested.Rheochord.An apparatus by means of which variable quantities of wire are throwninto the circuit; a rheostat using wire. (See Rheostat, Wheatstone's.)Rheometer.A galvanometer. (Obsolete.)472 STANDARD ELECTRICAL DICTIONARY.Rheomotor.A source of current; a current generator; a producer of potentialdifference. (Obsolete.)Rheophore.The portion of an active circuit capable of deflecting a magneticneedle. This properly includes all of the metallic conductor of acircuit. (Obsolete.)Rheoscope.A galvanoscope; an instrument for qualitatively detecting potentialdifference, fall or rise. (See Galvanoscope.)Rheostat.An adjustable resistance; an apparatus for changing the resistancewithout opening the circuit. Its action may depend on the introductionof variable lengths of mercury column, of some other liquid, or of wireinto a circuit. (See Rheostat, Wheatstone's.)Rheostat Arm.The third arm of known resistance in a Wheatstone bridge. (SeeProportionate Arms.)Rheostatic Machine.An apparatus for increasing potential difference. It consists of anumber of static condensers. They are charged in multiple arc or inparallel, and are discharged in series. Secondary batteries may be usedfor the charging; thus a static effect is produced from a galvanicbattery.Rheostat, Wheatstone's.This apparatus consists of two cylinders, one, A, made of brass, theother, B, of wood, with a spiral groove. At its end is a copper ring a.A fine brass wire has one end attached to this ring. Its other end isfastened at e, and it is wound as shown; n and o are binding screwsconnected, one with the cylinder-ring a, the other with the brasscylinder, A. The current entering at o, traverses the wire on B, asthere the windings are insulated by the grooves, thence it passes to mand by A, whose metal short circuits all the wire on it, to thebinding-post n. The handle, d, is turned one way or the other toregulate the length of the wire through which the current must pass. Oneach cylinder there is a square head, one of which is shown at c, sothat the handle can be shifted from one to the other as required; to Aif the wire is to be wound on that cylinder, to B if the reverse isdesired.Fig. 297. WHEATSTONE'S RHEOSTAT.473 STANDARD ELECTRICAL DICTIONARY.Rheotome.An automatic circuit breaker, one which rapidly opens and closes acircuit, as in the case of the primary of an induction coil aninterrupter. (Obsolete.)Rheotrope.A pole changer, current reverser, or commutator, g., such as thecommutator of an induction coil. (Obsolete.)Rhigolene.A petroleum product; a hydrocarbon of low boiling point. Its vapor isused in flashing (q. v.) carbon filaments for incandescent lamps.Rhumbs.In a mariners' compass, the thirty-two points, designated, north, northby east, north north east, etc. (See Compass Mariner's-Compass, Pointsof the.)Rhumkorff Coil.The induction coil, q. v.Rigidity, Molecular.The tendency of molecules to resist rotation or change of position; theassumed cause of magnetic coercive force, or retentivity.Ring Contact.A contact formed by a terminal clip in the shape of a ring, split or cutat one point so that its ends tend to spring together. The otherterminal is a bar which passes into the cut and is tightly pressed bythe elastic ring.Fig. 298. SWITCH WITH RING CONTACTS.474 STANDARD ELECTRICAL DICTIONARY.Ring, Faraday.A closed ring of iron used as the core of a transformer or inductioncoil. The term is derived from Faraday's classic experiment with such anapparatus when he produced a spark by induction in a secondary circuit.Roaring.A term applied to the noise sometimes produced in a voltaic arc, whenthe electrodes are close together and a heavy current is passing.Rocker.In a dynamo the movable piece, mounted concentrically with thecommutator, and carrying the rocker-arms and brush-holders. By moving itthe brushes are adjusted for proper lead.Rocker Arms.The arms projecting from a rocker and each carrying one of thebrush-holders.Roget's Spiral.An experimental apparatus for illustrating the mutual attraction ofcurrents going in like direction. A cylindrical helix or spiral of wireis suspended by one end. Its lower end just dips into a mercury cup. Anactive circuit is connected, one terminal to the upper end, the otherterminal to the mercury cup, bringing the apparatus in series into thecircuit. The current as it passes causes the coil to shorten, eachspiral attracting its neighbors. This breaks the circuit by drawing thelower end out of the mercury cup. The current being cut off the coilscease to attract each other, and the end dips into the mercury cupagain. This closes the circuit, the coils again attract each other andthe same sequence follows and is repeated over and over again. A brightspark is produced at each break of the mercury contact.Rotation of Liquids, Electro-dynamic.By passing a current through a liquid, such as dilute sulphuric acid, itrotates if exposed to the induction of a current flowing at right anglesto it. The condition resolves itself into a liquid traversed byhorizontal currents from centre to circumference or vice versa, rotatedby a current passing through a circular conductor below it.475 STANDARD ELECTRICAL DICTIONARY.Rotation of Liquids, Electro-magnetic.The rotation produced in a liquid carrying centripetal or centrifugalcurrents by an electromagnet. It is practically an intensification ofelectro-dynamic rotation. (See Rotation of Liquids, Electro-dynamic.)Rubber.In a frictional electric machine the cushion of leather which is pressedagainst the plate as it rotates.