convolutions in the primary wire than in the secondary. Such coils inpractice are used with the alternating current and then do not include acircuit breaker or condenser. They are employed in alternating currentsystem and in electric welding. (See Welding, Electric--Converter.)In the cut an inverted coil, as constructed for electric welding isshown. In it the primary coil is marked P; the secondary, merely a barof metal, is marked E, with terminals S, S; the heavy coils, I, of ironwire are the core; K is a screw for regulating the clamps; J, Z is asecond one for the same purpose, while between D and D' the heat isproduced for welding the bars, B, B', held in the clamps, C, C'. It willbe seen how great may be the difference in turns between the singlecircle of heavy copper rod or bar which is the secondary of the coil,and the long coil of wire forming the primary.Fig. 102. INVERTED INDUCTION COIL FOR ELECTRIC WELDING.137 STANDARD ELECTRICAL DICTIONARY.Coil, Induction, Telephone.An induction coil used in telephone circuits. It is placed in the box orcase near the transmitter. The primary is in circuit with themicrophone. The secondary is in circuit with the line and receivingtelephone. In the Bell telephone apparatus the primary of the inductioncoil is wound with No. 18 to 24 A. W. G. wire to a resistance of 1/2ohm; the secondary, with No. 36 wire to a resistance of 80 ohms. TheEdison telephone induction coil was wound with similar wires to aresistance of 3 to 4 ohms and of 250 ohms respectively.Coil, Magnetizing.A coil of insulated wire for making magnets; and for experimental uses;it has a short axis and central aperture of as small size as consistentwith the diameter of the bar to be magnetized, which has to pass throughit readily. The wire may be quite heavy, 2 or 3 millimeters (.08--.12inch) thick, and is cemented together with carpenter's glue, or withshellac or ethereal solution of gum copal. In use it is passed over thebar a few times while a heavy current is going through it. It is usedfor magic circles also. (See Circle, Magic.)Fig. 103. MAGNETIZING COIL.Coil, Resistance.A coil constructed for the purpose of offering a certain resistance to asteady current. This resistance may be for the purpose of carrying outquantitative tests, as in Wheatstone bridge work (see Wheatstone'sBridge), or simply to reduce the intensity of a current. For the firstclass of work the coils are wound so as to prevent the creation of amagnetic field. This is effected by first doubling the wire withoutbreaking it, and then starting at the bend the doubled wire, which isinsulated, is wound on a bobbin or otherwise until a proper resistanceis shown by actual measurement. The coils are generally contained or setin closed boxes with ebonite tops. Blocks of brass are placed on thetop, and one end from one coil and one end from the next connect withthe same block. By inserting a plug, P, so as to connect any two blocks,which have grooves reamed out for the purpose, the coil beneath will beshort circuited. German silver, platinoid or other alloy, q. v., isgenerally the material of the wire. A great object is to have a wirewhose resistance will be unaffected by heat.138 STANDARD ELECTRICAL DICTIONARY.Fig. 104. RESISTANCE COILS AND CONNECTIONS, SHOWING PLUG.Coil, Rhumkorff.The ordinary induction coil with circuit breaker, for use with originaldirect and constant current, is thus termed. (See Coil, Induction.)Synonym--Inductorium.Coil, Ribbon.A coil made of copper ribbon wound flatwise, often into a disc-likeshape, and insulated by tape or strips of other material interveningbetween the successive turns.Coils, Compensating.Extra coils on the field magnets of dynamos or motors, which coils arein series with the armature windings for the purpose of keeping thevoltage constant. In compound wound machines the regular series-woundcoil is thus termed. In a separately excited dynamo a coil of the samekind in circuit with the armature may be used as a compensator.Coils, Henry's.An apparatus used in repeating a classic experiment in electro-magneticinduction, due to Prof. Henry. It consists in a number of coils, thefirst and last ones single, the intermediate ones connected in pairs,and one of one pair placed on the top of one of the next pair. Onopening or closing the circuit of an end coil the induced effect goesthrough the series and is felt in the circuit of the other end coil.Prof. Henry extended the series so as to include seven successiveinductions, sometimes called inductions of the first, second, third andother orders. Frequently ribbon coils (see Coil, Ribbon,) are used inthese experiments.Coils, Sectioned.A device for prolonging the range of magnetic attraction. It consists ofa series of magnetizing coils traversed by an iron plunger. As it passesthrough them, the current is turned off the one in the rear or passingto the rear and turned into the next one in advance. The principle wasutilized in one of Page's electric motors about 1850, and later byothers. The port-electric railroad, q. v., utilizes the same principle.139 STANDARD ELECTRICAL DICTIONARY.Collecting Ring.In some kinds of generators instead of the commutator a pair ofcollecting rings of metal, insulated from the machine and from eachother, are carried on the armature shaft. A brush, q. v., presses oneach, and the circuit terminals connect to these two brushes. Such ringsare employed often on alternating current generators, where the currentdoes not have to be changed or commuted. Collecting rings with theirbrushes are used also where a current has to be communicated to arevolving coil or circuit as in the magnetic car wheel, the cut of whichis repeated here. The coil of wire surrounding the wheel and rotatingwith it has to receive current. This it receives through the twostationary brushes which press upon two insulated metallic rings,surrounding the shaft. The terminals of the coil connect one to eachring. Thus while the coil rotates it constantly receives current, thebrushes being connected to the actuating circuit.Fig. 105. MAGNETIC CAR WHEEL SHOWINGCOLLECTING RINGS AND BRUSHES.Collector.(a) A name for the brush, q. v., in mechanical electric generators, suchas dynamos, a pair of which collectors or brushes press on thecommutator or collecting rings, and take off the current.(b) The pointed connections leading to the prime conductor on a staticmachine for collecting the electricity; often called combs. The pointsof the combs or collectors face the statically charged rotating glassplate or cylinder of the machine.Colombin.The insulating material between the carbons in a Jablochkoff candle orother candle of that type. Kaolin was originally used. Later a mixtureof two parts calcium sulphate (plaster of Paris) and one part bariumsulphate (barytes) was substituted.The colombin was three millimeters (.12 inch) wide, and two millimeters(.08 inch) thick. (See Candle, Jablochkoff.)Column, Electric.An old name for the voltaic pile, made up of a pile of discs of copperand zinc, with flannel discs, wet with salt solution or dilute acid,between each pair of plates.140 STANDARD ELECTRICAL DICTIONARY.Comb.A bar from which a number of teeth project, like the teeth of a comb. Itis used as a collector of electricity from the plate of a frictional orinfluence electric machine; it is also used in a lightning arrester todefine a path of very high resistance but of low self-induction, for thelightning to follow to earth.Communicator.The instrument by which telegraph signals are transmitted is sometimesthus termed.Commutator.In general an apparatus for changing. It is used on electric currentgenerators, and motors, and on induction coils, and elsewhere, forchanging the direction of currents, and is of a great variety of types.Synonym--Commuter (but little used).Fig. 106. DYNAMO OR MOTOR COMMUTATOR.Commutator Bars.The metallic segments of a dynamo or motor commutator.Commutator, Flats in.A wearing away or lowering in level of one or more metallic segments ofa commutator. They are probably due in many cases to sparking, set up byperiodic springing in the armature mounting, or by defective commutatorconnections.Commutator of Current Generators and Motors.In general a cylinder, formed of alternate sections of conducting andnon-conducting material, running longitudinally or parallel with theaxis. Its place is on the shaft of the machine, so that it rotatestherewith. Two brushes, q. v., or pieces of conducting material, pressupon its surface.141 STANDARD ELECTRICAL DICTIONARY.As a part of electric motors and generators, its function is to collectthe currents produced by the cutting of lines of force so as to causethem all to concur to a desired result. The cut shows the simplest formof commutator, one with but two divisions. Its object may be to enable acurrent of constant direction to be taken from a rotating armature, inwhich the currents alternate or change direction once in each rotation.It is carried by the shaft A of the armature and rotates with it. Itconsists of two leaves, S S, to which the terminals of the armature areconnected. Two springs, W W, the terminals of the outer circuit, pressagainst the leaves. The springs which do this take off the current. Itis so placed, with reference to the springs and armature, that just asthe current changes in direction, each leaf changes from one spring tothe other. Thus the springs receive constant direction currents. Thechanging action of this commutator appears in its changing the characterof the current from alternating to constant. Were two insulatedcollecting rings used instead of a commutator, the current in the outercircuit would be an alternating one. On some dynamos the commutator hasa very large number of leaves.Taking the Gramme ring armature, there must be as many divisions of thecommutator as there are connections to the coils. In this case thefunction of the commutator is simply to lessen friction, for the brushescould be made to take current from the coils directly outside of theperiphery of the ring.Commutator, Split Ring.A two-division commutator for a motor; it consists of two segments ofbrass or copper plate, bent to arcs of a circle, and attached to aninsulating cylinder. They are mounted on the revolving spindle, whichcarries the armature, and acts as a two part commutator. For an exampleof its application, see Armature, Revolving, Page's. (See also Fig.107.)Fig. 107. SECTION OF SPLIT RING COMMUTATOR, WITH BRUSHES.Compass.An apparatus for utilizing the directive force of the earth upon themagnetic needle. It consists of a circular case, within which is poiseda magnetized bar of steel. This points approximately to the north, andis used on ships and elsewhere to constantly show the direction of themagnetic meridian. Two general types are used. In one the needle ismounted above a fixed "card" or dial, on which degrees or points of thecompass, q. v., are inscribed. In the other the card is attached to theneedle and rotates with it. The latter represents especially the typeknown as the mariner's compass. (See Compass, Mariner's--Compass,Spirit, and other titles under compass, also Magnetic Axis--MagneticElements.) The needle in good compasses carries for a bearing at itscentre, a little agate cup, and a sharp brass pin is the point ofsupport.Compass, Azimuth.A compass with sights on one of its diameters; used in determining themagnetic bearing of objects.142 STANDARD ELECTRICAL DICTIONARY.Compass Card.The card in a compass; it is circular in shape, and its centre coincideswith the axis of rotation of the magnetic needle; on it are marked thepoints of the compass, at the ends generally of star points. (SeeCompass, Points of the.) It may be fixed, and the needle may be poisedabove it, or it may be attached to the needle and rotate with it.Compass, Declination.An instrument by which the magnetic declination of any place may bedetermined. It is virtually a transit instrument and compass combined,the telescope surmounting the latter. In the instrument shown in thecut, L is a telescope mounted by its axis, X, in raised journals withvernier, K, and arc x, for reading its vertical angle, with level n. Theazimuth circle, Q, R, is fixed. A vernier, V is carried by the box, A,E, and both turn with the telescope. A very light lozenge-shapedmagnetic needle, a, b, is pivoted in the exact centre of the graduatedcircles, Q R, and M. The true meridian is determined by any convenientastronomical method, and the telescope is used for the purpose. Thevariation of the needle from the meridian thus determined gives themagnetic declination.FIG. 108. DECLINATION COMPASS.Compass, Inclination.A magnetic needle mounted on a horizontal axis at its centre of gravity,so as to be free to assume the dip, or magnetic inclination, when placedin the magnetic meridian. It moves over the face of a vertical graduatedcircle, and the frame also carries a spirit level and graduatedhorizontal circle. In use the frame is turned until the needle isvertical. Then the axis of suspension of the needle is in the magneticmeridian. The vertical circle is then turned through 90° of the horizon,which brings the plane of rotation of the needle into the magneticmeridian, when it assumes the inclination of the place.143 STANDARD ELECTRICAL DICTIONARY.Compass, Mariner's.A compass distinguished by the card being attached to and rotating withthe needle. A mark, the "lubber's mark" of the sailors is made upon thecase. This is placed so that the line connecting it, and the axis ofrotation of the card is exactly in a plane, passing through the keel ofthe ship. Thus however the ship may be going, the point of the cardunder or in line with the "lubber's mark," shows how the ship ispointing. The case of the mariner's compass is often bowl-shaped andmounted in gimbals, a species of universal joint, so as to bc alwayshorizontal. (See Compass, Spirit-Gimbals.)FIG. 109. MARINER'S COMPASS.Compass, Points of the.The circle of the horizon may bc and is best referred to angulardegrees. It has also been divided into thirty-two equiangular and namedpoints. A point is 11.25°. The names of the points are as follows:North, North by East, North North-east, North-east by North, North-east,North-east by East, East North-east, East by North, East, East by South,East South-east, South-east by East, South-east, South-east by South,South South-east, South by East, South, South by West, South South-west,South-west by South, South-west, South-west by West, West South-west,West by South, West, West by North, West North-west, North-west by West,North-west, North West by North, North North-west, North by West. Theyare indicated by their initials as N. N. W., North North-west, N. by W.,North by West.Compass, Spirit.A form of mariner's compass. The bowl or case is hermetically sealed andfilled with alcohol or other nonfreezing liquid. The compass card ismade with hollow compartments so as nearly to float. In this way thefriction of the pivot or point of support is greatly diminished, and thecompass is far more sensitive.Compass, Surveyor's.A species of theodolite; a telescope with collimation lines, mountedabove a compass, so as to be applicable for magnetic surveys. Its use isto be discouraged on account of the inaccuracy and changes indeclination of the magnetic needle.144 STANDARD ELECTRICAL DICTIONARY.Compensating Resistances.In using a galvanometer shunt the total resistance of the circuit isdiminished so that in some cases too much current flows through it; insuch case additional resistance, termed as above, is sometimesintroduced in series. The shunt in parallel with the galvanometer isthus compensated for, and the experimental or trial circuit does nottake too much current.Complementary Distribution.Every distribution of electricity has somewhere a correspondingdistribution, exactly equal to it of opposite electricity; the latter isthe complimentary distribution to the first, and the first distributionis also complimentary to it.Component.A force may always be represented diagrammatically by a straight line,terminating in an arrow-head to indicate the direction, and of length torepresent the intensity of the force. The line may always be assumed torepresent the diagonal of a parallelogram, two of whose sides arerepresented by lines starting from the base of the arrow, and of lengthfixed by the condition that the original force shall be the diagonal ofthe parallelogram of which they are two contiguous sides; such lines arecalled components, and actually represent forces into which the originalforce may always be resolved. The components can have any direction.Thus the vertical component of a horizontal force is zero; itshorizontal component is equal to itself. Its 450 component is equal tothe square root of one-half of its square.Condenser.An appliance for storing up electrostatic charges: it is also called astatic accumulator. The telegraphic condenser consists of a box packedfull of sheets of tinfoil. Between every two sheets is a sheet ofparaffined paper, or of mica. The alternate sheets of tinfoil areconnected together, and each set has its own binding post. (SeeAccumulator, Electrostatic.)Condenser, Sliding.An apparatus representing a Leyden jar whose coatings can be slid pasteach other. This diminishes or increases the facing area, andconsequently in almost exactly similar ratio diminishes or increases thecapacity of the condenser.Conductance.The conducting power of a given mass of specified material of specifiedshape and connections. Conductance varies in cylindrical or prismaticconductors, inversely as the length, directly as the cross-section, andwith the conductivity of the material. Conductance is an attribute ofany specified conductor, and refers to its shape, length and otherfactors. Conductivity is an attribute of any specified material withoutdirect reference to its shape, or other factors.Conduction.The process or act of conducting a current.145 STANDARD ELECTRICAL DICTIONARY.Conductivity.The relative power of conducting the electric current possessed bydifferent substances. A path for the current through the ether is openedby the presence of a body of proper quality, and this quality, probablycorrelated to opacity, is termed conductivity. There is no perfectconductor, all offer some resistance, q. v., and there is hardly anyperfect non-conductor. It is the reverse and reciprocal of resistance.Conductivity, Specific.The reciprocal of specific resistance. (See Resistance--Specific.)Conductivity, Unit of.The reciprocal of the ohm; it is a more logical unit, but has never beengenerally adopted; as a name the title mho (or ohm written backwards)has been suggested by Sir William Thomson, and provisionally adopted.Conductivity, Variable.The conductivity for electric currents of conductors varies with theirtemperature, with varying magnetization, tension, torsion andcompression.Conductor.In electricity, anything that permits the passage of an electriccurrent. Any disturbance in the ether takes the form of waves becausethe ether has restitutive force or elasticity. In a conductor, on theother hand, this force is wanting; it opens a path through the ether anda disturbance advances through it from end to end with a wave front, butwith no succession of waves. This advance is the beginning of what istermed a current. It is, by some theorists, attributed to impulses givenat all points along the conductor through the surrounding ether, so thata current is not merely due to an end thrust. If ether waves preclude acurrent on account of their restitutive force, ether waves cannot bemaintained in a conductor, hence conductors should be opaque to light,for the latter is due to ether waves. This is one of the more practicalevery day facts brought out in Clerk Maxwell's electromagnetic theory oflight. The term conductor is a relative one, as except a vacuum there isprobably no substance that has not some conducting power. For relativeconducting power, tables of conductivity, q. v., should be consulted.The metals beginning with silver are the best conductors, glass is oneof the worst.[Transcriber's note: See "ether" for contemporary comments on this nowdiscarded concept.]Conductor, Anti-Induction.A current conductor arranged to avoid induction from other lines. Manykinds have been invented and made the subject of patents. A fairapproximation may be attained by using a through metallic circuit andtwisting the wires composing it around each other. Sometimes concentricconductors, one a wire and the other a tube, are used, insulated, oneacting as return circuit for the other.Conductor, Conical.A prime conductor of approximately conical shape, but rounded on allpoints and angles. Its potential is highest at the point.146 STANDARD ELECTRICAL DICTIONARY.Conductor, Imbricated.A conductor used in dynamo armatures for avoiding eddy currents, made bytwisting together two or more strips of copper.Conductor, Prime.A body often cylindrical or spherical in shape, in any case with nopoints or angles, but rounded everywhere, whose surface, if theconductor itself is not metallic, is made conducting by tinfoil or goldleaf pasted over it. It is supported on an insulating stand and is usedto collect or receive and retain static charges of electricity.Conductors, Equivalent.Conductors of identical resistance. The quotient of the length dividedby the product of the conductivity and cross-section must be the same ineach, if each is of uniform diameter.Conjugate. adj.Conjugate coils or conductors are coils placed in such relation that thelines of force established by one do not pass through the coils of theother. Hence variations of current in one produce no induced currents inthe other.Connect. v.To bring two ends of a conductor together, or to bring one end of aconductor in connection with another, or in any way to bring about anelectrical connection.Connector.A sleeve with screws or other equivalent device for securing the ends ofwires in electrical contact. A binding-post, q. v., is an example.Sometimes wire spring-catches are used, the general idea being a devicethat enables wires to be connected or released at will without breakingoff or marring their ends. The latter troubles result from twistingwires together.Consequent Poles.A bar magnet is often purposely or accidentally magnetized so as to haveboth ends of the same polarity, and the center of opposite polarity. Thecenter is said to comprise two consequent poles. (See Magnet,Anomalous.)Conservation of Electricity.As every charge of electricity has its equal and opposite chargesomewhere, near or far, more or less distributed, the sum of negative isequal always to the sum of positive electrical charges. For thisdoctrine the above title was proposed by Lippman.Contact Breaker.Any contrivance for closing a circuit, and generally for opening andclosing in quick succession. An old and primitive form consisted of avery coarsely cut file. This was connected to one terminal, and theother terminal was drawn over its face, making and breaking contact asit jumped from tooth to tooth. (See Circuit Breaker--do. Automatic,etc.--do. Wheel-do. Pendulum.)147 STANDARD ELECTRICAL DICTIONARY.Contact, Electric.A contact between two conductors, such that a current can flow throughit. It may be brought about by simple touch or impact between the endsor terminals of a circuit, sometimes called a dotting contact, or by asliding or rubbing of one terminal on another, or by a wheel rolling ona surface, the wheel and surface representing the two terminals.There are various descriptions of contact, whose names areself-explanatory. The term is applied to telegraph line faults also, andunder this, includes different descriptions of contact with neighboringlines, or with the earth.Contact Electricity.When two dissimilar substances are touched they assume differentelectric potentials. If conductors, their entire surfaces are affected;if dielectrics, only the surfaces which touch each other. (See ContactTheory.)Contact Faults.A class of faults often called contacts, due to contact of the conductorof a circuit with another conductor. A full or metallic contact is wherepractically perfect contact is established; a partial contact andintermittent contact are self-explanatory.Contact Point.A point, pin or stud, often of platinum, arranged to come in contactwith a contact spring, q. v., or another contact point or surface, underany determined conditions.Contact Potential Difference.The potential difference established by the contact of two dissimilarsubstances according to the contact theory, q. v.Contact Series.An arrangement or tabulation of substances in pairs, each intermediatesubstance appearing in two pairs, as the last member of the first, andfirst member of the succeeding pair, with the statement of the potentialdifference due to their contact, the positively electrified substancecoming first. The following table of some contact potentials is due toAyrton and Perry:CONTACT SERIES.Difference of Potential in Volts.Zinc--Lead .210Lead--Tin .069Tin--Iron .313Iron--Copper .146Copper--Platinum .238Platinum-Carbon .113The sum of these differences is 1.089, which is the contact potentialbetween zinc and carbon.Volta's Law refers to this and states that--The difference of potential produced by the contact of any twosubstances is equal to the sum of the differences of potentialsbetween the intervening substances in the contact series.It is to be remarked that the law should no longer be restricted to orstated only for metals.148 STANDARD ELECTRICAL DICTIONARY.Contact-spring.A spring connected to one lead of an electric circuit, arranged to pressagainst another spring, or contact point, q. v., under any conditionsdetermined by the construction of the apparatus. (See Bell,Electric--Coil, Induction.)Contact Theory.A theory devised to explain electrification, the charging of bodies byfriction, or rubbing, and the production of current by the voltaicbattery. It holds that two bodies, by mere contact become oppositelyelectrified. If such contact is increased in extent by rubbing together,the intensity of their electrification is increased. Thiselectrification is accounted for by the assumption of different kineticenergy, or energy of molecular motion, possessed by the two bodies;there being a loss and gain of energy, on the two sides respectively,the opposite electrifications are the result. Then when separated, thetwo bodies come apart oppositely electrified.The above accounts for the frictional production of electricity. In thevoltaic battery, a separation of the atoms of hydrogen and oxygen, andtheir consolidation into molecules occurs, and to such separation andthe opposite electrification of the electrodes by the oxygen andhydrogen, the current is attributed, because the hydrogen goes to oneelectrode, and the oxygen to the other, each giving up or sharing itsown charge with the electrodes to which it goes. If zinc is touched tocopper, the zinc is positively and the copper negatively electrified. Inthe separation of hydrogen and oxygen, the hydrogen is positively andthe oxygen negatively electrified. In the battery, the current is due tothe higher contact difference of oxygen and hydrogen compared to thatbetween zinc and copper. It will be seen that the two contact actions ina battery work against each other, and that the current is due to adifferential contact action. The zinc in a battery is electrifiednegatively because the negative electrification of the oxygen is greaterin amount than its own positive electrification due to contact with thecopper.Contractures.A muscular spasm or tetanus due to the passage of a current ofelectricity; a term in electro-therapeutics.Controlling Field.The magnetic or electro-magnetic field, which is used in galvanometersto control the magnetic needle, tending to restore it to a definiteposition whenever it is turned therefrom. It may be the earth's field orone artificially produced.Controlling Force.In galvanometers and similar instruments, the force used to bring theneedle or indicator back to zero. (See ControllingField--Electro-Magnetic Control--Gravity Control--MagneticControl--Spring Control.)149 STANDARD ELECTRICAL DICTIONARY.Convection, Electric.The production of blasts or currents of air (convection streams) frompoints connected to statically charged conductors. The term is sometimesapplied to electric convection of heat. (See Convection of Heat,Electric.)Convection, Electrolytic.The resistance of acidulated water as a true conductor is known to bevery, almost immeasurably, high. As an electrolytic, its resistance isvery much lower. Hence the current produced between immersed electrodesis theoretically almost null, unless the difference of potential betweenthem is high enough to decompose the liquid. Yet a feeble current toogreat for a true conduction current is sometimes observed when twoelectrodes with potential difference too low to cause decomposition areimmersed in it. Such a current is termed an electrolytic convectioncurrent. It is supposed to be due to various causes. Some attribute itto the presence of free oxygen from the air, dissolved in the water withwhich the hydrogen combines. Others attribute it to the diffusion of thegases of decomposition in the solution; others assume a partialpolarization of the molecules without decomposition. Other theories aregiven, all of which are unsatisfactory. The term is due to Helmholtz.Convection of Heat, Electric.The effect of a current upon the distribution of heat in an unevenlyheated conductor. In some, such as copper, the current tends to equalizethe varying temperatures; the convection is then said to be positive, ascomparable to that of water flowing through an unequally heated tube. Inothers, such as platinum or iron, it is negative, making the heatedparts hotter, and the cooler parts relatively cooler.The effect of the electric current in affecting the distribution of heatin unequally heated metal (Thomson's effect. q. v.), is sometimes sotermed. If a current passes through unequally heated iron it tends toincrease the difference of temperature, and the convection is negative;in copper it tends to equalize the temperature, and the convection ispositive.Converter.An induction coil used with the alternating current for changingpotential difference and inversely therewith the available current. Theygenerally lower the potential, and increase the current, and are placedbetween the primary high potential system that connects the houses withthe central station, and the secondary low potential system within thehouses. A converter consists of a core of thin iron sheets, wound with afine primary coil of many convolutions, and a coarse secondary coil offew convolutions. The ratio of convolutions gives the ratio of maximumpotential differences of their terminals between the primary andsecondary coils. The coil may be jacketed with iron to increase thepermeance. (See Alternating Current System.)Fig. 110. FERRANTI'S CONVERTER OR TRANSFORMER.Fig. 111. SWINBURNE'S HEDGEHOG TRANSFORMER.150 STANDARD ELECTRICAL DICTIONARY.Co-ordinates, System of.A system for indicating the position of points in space by reference tofixed lines, intersecting at a determined and arbitrary point 0, termedthe origin of co-ordinates. In plane rectangular co-ordinates two linesare drawn through the origin, one horizontal, termed the axis ofabscissas, or axis of X. All distances measured parallel to it, ifunknown, are indicated by x, and are termed abscissas. The other axis isvertical, and is termed the axis of ordinates, or axis of Y. Alldistances measured parallel to it, if unknown, are indicated by y andare termed ordinates. Thus by naming its abscissa and ordinate a pointhas its position with reference to the axes determined, and byindicating the relation between a point, line or curve, and a system ofabscissas and ordinates, the properties of a line or curve can beexpressed algebraically. Co-ordinates may also be inclined to each otherat any other angles, forming oblique co-ordinates; relations may beexpressed partly in angles referred to the origin as a centre, givingpolar co-ordinates. For solid geometry or calculations in threedimensions, a third axis, or axis of Z, is used, distances parallel towhich if unknown are indicated by z.Fig. 112. AXES OF CO-ORDINATES.151 STANDARD ELECTRICAL DICTIONARY.Cooling Box.In a hydroelectric machine, q. v., a conduit or chest through which thesteam passes on its way to the nozzles. Its object is to partiallycondense the steam so as to charge it with water vesicles whose frictionagainst the sides of the nozzles produces the electrification .152 STANDARD ELECTRICAL DICTIONARY.Copper.A metal; one of the elements. Symbol, Cu; atomic weight, 63.5;equivalent, 63.5 and 31.75; valency, 1 and 2; specific gravity, 8.96.It is a conductor of electricity, whose conductivity is liable tovary greatly on account of impurities.Annealed. Hard drawn.Relative resistance (Silver = 1), 1.063 1.086Specific resistance, 1.598 1.634 microhms.Resistance of a wire at 0° C. (32° F.),Annealed. Hard Drawn.(a) 1 foot long, weighing 1 grain, .2041 ohms .2083 ohms.(b) 1 foot long, 1/1000 inch thick, 9.612 " 9.831 "(c) 1 meter long, weighing 1 gram, .1424 " .1453 "(d) 1 meter long, 1 millimeter thick, .02034 " .02081 "microhm. microhm.Resistance of 1 inch cube at 0°C. (32° F.) .6292 .6433Percentage of resistance change,per 1° C. (1.8° F.) at about 20° C. (68° F.) = 0.388 per cent.Electro-chemical Equivalent (Hydrogen = .0105) Cuprous .6667Cupric .3334In electricity it has been very extensively used as the negative plateof voltaic batteries. It has its most extensive application asconductors for all classes of electrical leads.Copper Bath.A solution of copper used for depositing the metal in the electroplatingprocess. For some metals, such as zinc or iron, which decompose coppersulphate solution, special baths have to be used.The regular bath for copper plating is the following:To water acidulated with 8 to 10 percent. of sulphuric acid as muchcopper sulphate is added as it will take up at the ordinary temperature.The saturated bath should have a density of 1.21. It is used cold and iskept in condition by the use of copper anodes, or fresh crystals may beadded from time to time.For deposition on zinc, iron, tin and other metals more electropositivethan copper, the following baths may be used, expressed in parts byweight:TinIron and Steel. Cast IronCold Hot. and Zinc. Zinc.Sodium Bisulphate, 500 200 300 100Potassium Cyanide, 500 700 500 700Sodium Carbonate, 1000 500 --- ---Copper Acetate, 475 500 350 450Aqua Ammoniae, 350 300 200 150Water, 2500 2500 2500 2500These are due to Roseleur.153 STANDARD ELECTRICAL DICTIONARY.Copper Stripping Bath.There is generally no object in stripping copper from objects. It can bedone with any of the regular copper baths using the objects to bestripped as anode. The danger of dissolving the base itself and therebyinjuring the article and spoiling the bath is obvious.Cord Adjuster.A device for shortening or lengthening the flexible cord, or flexiblewire supplying the current, and by which an incandescent lamp issuspended. It often is merely a little block of wood perforated with twoholes through which the wires pass, and in which they are retained inany desired position by friction and their own stiffness.Fig. 113. FLEXIBLE CORD ADJUSTER.Cord, Flexible.A pair of flexible wire conductors, insulated lightly, twisted togetherand forming apparently a cord. They are used for minor services, such assingle lamps and the like, and are designated according to the servicethey perform, such as battery cords, dental cords (for supplying dentalapparatus) and other titles.Core.(a) The conductor or conductors of an electric cable. (See Cable Core.)(b) The iron mass, generally central in an electro-magnet or armature,around which the wire is coiled. It acts by its high permeance toconcentrate or multiply the lines of force, thus maintaining a moreintense field. (See Armature--Magnet, Electro--Magnet, Field--Core,Laminated). In converters or transformers (See Converter) it oftensurrounds the wire coils.Core-discs.Discs of thin wire, for building up armature cores. (See LaminatedCore.) The usual form of core is a cylinder. A number of thin discs ofiron are strung upon the central shaft and pressed firmly together byend nuts or keys. This arrangement, it will be seen, gives a cylinder asbasis for winding the wire on.Core-discs, Pierced.Core-discs for an armature of dynamo or motor, which are pierced aroundthe periphery. Tubes of insulating material pass through the peripheralholes, and through these the conductors or windings are carried. Theconductors are thus embedded in a mass of iron and are protected fromeddy currents, and they act to reduce the reluctance of the air gaps.From a mechanical point of view they are very good. For voltages over100 they are not advised.Synonym--Perforated Core-discs.154 STANDARD ELECTRICAL DICTIONARY.Core-discs, Segmental.Core-discs made in segments, which are bolted together to form acomplete disc or section of the core. The plan is adopted principally onlarge cores. The discs thus made up are placed together to form the coreexactly as in the case of ordinary one piece discs.Fig. 114. PIERCED OR PERFORATED CORE-DISC.Core-discs, Toothed.Core-discs of an armature of a dynamo or motor, which discs are cut intonotches on the periphery. These are put together to form the armaturecore, with the notches corresponding so as to form a series of groovesin which the wire winding is laid. This construction reduces the actualair-gaps, and keeps the wires evenly spaced. Distance-pieces ofbox-wood, m, m, are sometimes used to lead the wires at the ends of thearmature.Fig. 115. TOOTHED CORE-DISC.Core, Laminated.A core of an armature, induction coil or converter or other similarconstruction, which is made up of plates insulated more or lessperfectly from each other. The object of lamination is to prevent theformation of Foucault currents. (See Currents, Foucault.) As insulation,thin shellacked paper may be used, or sometimes the superficialoxidation of the plates alone is relied on. The plates, in general, arelaid perpendicular to the principal convolutions of the wire, orparallel to the lines of force. The object is to break up currents, andsuch currents are induced by the variation in intensity of the field offorce, and their direction is perpendicular to the lines of force, orparallel to the inducing conductors.A core built up of core discs is sometimes termed a tangentiallylaminated core. Made up of ribbon or wire wound coil fashion, it istermed a radially laminated core.155 STANDARD ELECTRICAL DICTIONARY.Core Ratio.In a telegraph cable the ratio existing between the diameter of theconducting core and the insulator. To get a ratio approximately accuratein practical calculations, the diameter of the core is taken at 5 percent. less than its actual diameter. The calculations are thosereferring to the electric constants of the cable, such as its staticcapacity and insulation resistance.Core, Ribbon.For discoidal ring-shaped cores of armatures, iron ribbon is often usedto secure lamination and prevent Foucault currents.Synonym--Tangentially Laminated Core.Core, Ring.A core for a dynamo or motor armature, which core forms a complete ring.Core, Stranded.In an electric light cable, a conducting core made up of a group ofwires laid or twisted together.Core, Tubular.Tubes used as cores for electro-magnets. For very small magnetizingpower, tubular cores are nearly as efficient as solid ones in straightmagnets, because the principal reluctance is due to the air-path. Onincreasing the magnetization the tubular core becomes less efficientthan the solid core, as the reluctance of the air-path becomesproportionately of less importance in the circuit.Corpusants.The sailors' name for St. Elmo's Fire, q. v.Coulomb.The practical unit of quantity of electricity. It is the quantity passedby a current of one ampere intensity in one second. It is equal to 1/10the C. G. S. electro-magnetic unit of quantity, and to 3,000,000,000 C.G. S. electrostatic units of quantity. It corresponds to thedecomposition of .0935 milligrams of water, or to the deposition of1.11815 milligrams of silver.[Transcriber's note: A coulomb is approximately 6.241E18 electrons. Twopoint charges of one coulomb each, one meter apart, exerts a force of900,000 metric tons.]Coulomb's Laws of Electrostatic Attraction and Repulsion.1. The repulsions or attractions between two electrified bodies are inthe inverse ratio of the squares of their distance.2. The distance remaining the same, the force of attraction or repulsionbetween two electrified bodies is directly as the product of thequantities of electricity with which they are charged.156 STANDARD ELECTRICAL DICTIONARY.Counter, Electric.A device for registering electrically, or by electro-magnetic machinery,the revolutions of shafts, or any other data or factors.Counter-electro-motive Force.A potential difference in a circuit opposed to the main potentialdifference, and hence, resisting the operation of the latter, anddiminishing the current which would be produced without it. It appearsin electric motors, which, to a certain extent, operate as dynamos andreduce the effective electro-motive force that operates them. Itappears in the primary coils of induction coils, and when the secondarycircuit is open, is almost equal to the main electro-motive force, sothat hardly any current can go through them under such conditions. Itappears in galvanic batteries, when hydrogen accumulates on the copperplate, and in other chemical reactions. A secondary battery is chargedby a current in the reverse direction to that which it would normallyproduce. Its own potential difference then appears as acounter-electro-motive force.Synonym--Back Electro-motive Force.Counter-electro-motive Force of Polarization.To decompose a solution by electrolysis, enough electro-motive force isrequired to overcome the energy of composition of the moleculedecomposed. A part of this takes the form of a counter-electromotiveforce, one which, for a greater or less time would maintain a current inthe opposite direction if the original source of current were removed.Thus in the decomposition of water, the electrodes become covered, onewith bubbles of oxygen, the others with bubbles of hydrogen; thiscreates a counter E. M. F. of polarization. In a secondary battery, theworking current may be defined as due to this cause.Synonym--Back Electro-motive Force of Polarization.Couple.Two forces applied to different points of a straight line, when opposedin direction or unequal in amount, tend to cause rotation about a pointintermediate between their points of application and lying on thestraight line. Such a pair constitute a couple.Couple, Voltaic or Galvanic.The combination of two electrodes, and a liquid or liquids, theelectrodes being immersed therein, and being acted on differentially bythe liquid or liquids. The combination constitutes a source ofelectro-motive force and consequently of current. It is the galvanic orvoltaic cell or battery. (See Battery, Voltaic--Contact