Chapter I: II (6)

If the factors differ in sign, it is generally best to leave the addition or subtraction to be simply expressed. However, by following the above rule, it can be done. Thus:

Add
5 X 10^-2 and 5 X 10^3.
5 X 10^3 = 5 X 10^5 X 10^-2
(5 X 10^5 X 10^-2) + (5 X 10^-2) = 500005 X 10^-2

This may be reduced to a fraction 500000/100 = 5000.05.

To multiply add the exponents of the factors, for the new factor, and multiply the characteristics for a new characteristic. The exponents must be added algebraically; that is, if of different signs the numerically smaller one is subtracted from the other one, and its sign is given the new exponent.

Thus;
(25 X 10^6) X (9 X 10^8) = 225 X 10^14.
(29 X 10^ -8) X (11 X 10^7) = 319 X 10^-1
(9 X 10^8) X (98 X 10^2) = 882 X 10^1

529 STANDARD ELECTRICAL DICTIONARY.

To divide, subtract (algebraically) the exponent of the divisor from that of the dividend for the exponent of the new factor, and divide the characteristics one by the other for the new characteristic. Algebraic subtraction is effected by changing the sign of the subtrahend, subtracting the numerically smaller number from the larger, and giving the result the sign of the larger number. (Thus to subtract 7 from 5 proceed thus; 5 - 7 = -2.)

Thus;
(25 X 10^6) / (5 X 10^8) = 5 X 10^-2
(28 X 10^-8) / (5 X 10^3) = 5.6 X 10^-11

[Transcriber's note: I have replaced ordinary exponential notation by the more compact and simpler "programming" representation. The last two example would be: 25E6 / 5E8 = 5E-2 28E-8 / 5E3 = 5.6E-11 ]

Tension. Electro-motive force or potential difference in a current system is often thus termed. It is to be distinguished from intensity or current strength, which word it too greatly resembles.

Tension, Electric. (a) The condition an electrified body is brought into by electrification, when each molecule repels its neighbor. The condition is described as one of self-repulsion.

(b) The voltage or potential difference of a circuit is also thus termed.

Terminal. The end of any open electric circuit, or of any electric apparatus; as the terminals of a circuit, dynamo, or battery.

Terminal Pole. In telegraph line construction the last pole of a series; one beyond which the line is not carried. Such pole, as the pull of the wires is all in one direction, requires special staying or support. The regular line poles are free from this strain, as the wire pulls in both directions.

Tetanus, Acoustic. A term in electro-therapeutics. An effect produced on a nerve by very rapidly alternating induced currents. The currents are produced by an induction coil with a vibrator giving a musical note. This is a species of gauge of proper frequency of alternations.

Theatrophone. An apparatus worked by automatic paying machinery by which a telephone connection is made with a theatre or opera by the deposition of a coin in a slot.

Therm. A unit of heat. It has been proposed by the British Association and amounts to a redefinition of the smaller calorie. It is the amount of heat required to raise the temperature of one gram of water one degree centigrade, starting at the temperature of maximum density of water.

530 STANDARD ELECTRICAL DICTIONARY.

Thermaesthesiometer. An electro-therapeutic instrument for testing the sensitiveness of the surface of the body to changes of temperature. Vessels of mercury are provided with thermometers to indicate their temperature. One vessel is surrounded by an electric conductor wound in a number of turns. The temperature is raised by passing a current through this. By successive applications of the vessels to the same spot upon the skin the power of differentiating temperatures is determined.

Thermo Call. (a) An electric alarm or call bell operated by thermo-electric currents. It may serve as a fire alarm or heat indicator, always bearing in mind the fact that differential heat is the requisite in a thermo-electric couple.

(b) See Thermo-electric Call.

Thermo-chemical Battery. A voltaic battery in which the electro-motive force is generated by chemical action induced by heat.

The chemical used generally is sodium nitrate or potassium nitrate. The positive plate is carbon. On heating the battery the nitrate attacks the carbon, burning it and produces potential difference. For negative plate some metal unattacked by the nitrate may be employed.

Fig. 330. POUILLET'S THERMO-ELECTRIC BATTERY.

Thermo-electric Battery or Pile. A number of thermo-electric couples q. v., connected generally in series.

In Nobili's pile the metals are bismuth and antimony; paper bands covered with varnish are used to insulate where required. In Becquerel's pile copper sulphide (artificial) and German silver, (90 copper, 10 nickel) are the two elements. The artificial copper sulphide is made into slabs 4 inches long, 3/4 inch wide, and 1/2 inch thick (about). Water is used to keep one set of junctions cool, and gas flames to heat the other set. In Fig. 331, c, d represent the binding screws. The couples are mounted on a vertical standard, with adjusting socket and screw B, so that its lower end can be immersed in cold water, or raised therefrom as desired.

531 STANDARD ELECTRICAL DICTIONARY.

FIG. 331. BECQUEREL'S THERMO-ELECTRIC BATTERIES.

Fig. 332 shows one couple of the battery. S is artificial antimony sulphide; M is German silver; m is a protecting plate of German silver to save the sulphide from wasting in the flame.

Fig. 332. ELEMENTS OF BECQUEREL'S THERMOELECTRIC BATTERIES.

Clamond's pile has been used in practical work. The negative element is an alloy of antimony, 2 parts, zinc, 1 part. The positive element is tin plate. Mica in some parts, and a paste of soluble glass and asbestus in other parts are used as insulators. They are built up so as to form a cylinder within which the fire is maintained. The air is relied on to keep the outer junctions cool. The temperature does not exceed 200° C. (392° F.)

Sixty such elements have an electro-motive force of 300 volts and an internal resistance of 1.5 ohms. Such a battery requires the consumption of three cubic feet of gas per hour. (See Currents, Thermo-electric. )

532 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Call. A thermostat arranged to ring a bell or to give some indication when the temperature rises or falls beyond certain points. It may be a compound bar of brass and steel fixed at one end and free for the rest of its length. Its end comes between two adjustable contacts. As the temperature rises it bends one way (away from the brass side) and, if hot enough, touching a contact gives one signal. If the temperature falls it curves the other way, and if cold enough touches the other contact, giving another signal. (See Thermostat, Electric.)

Thermo-electric Couple. If two dissimilar conductors form adjacent parts of a closed circuit, and their junction is at a different temperature than that of the rest of the circuit, a current will result. Such pair of conductors are called a thermo-electric couple. They may be joined in series so as to produce considerable electro-motive force. (See Thermo-electricity and other titles in thermo-electricity.)

The efficiency of a thermo-electric couple according to the second law of thermo-dynamics is necessarily low--not over 10 per cent.

Thermo-electric Diagram. A diagram indicating the change in potential difference for a fixed difference of temperature between different metals at different temperatures. It is laid out with rectangular co-ordinates. On one axis temperatures are laid off, generally on the axis of abscissas. On the other axis potential differences are marked. Different lines are then drawn, one for each metal, which show the potential difference, say for one degree centigrade difference of temperature between their junctions, produced at the different temperatures marked on the axis of abscissas.

Fig. 333· THERMO-ELECTRIC DIAGRAM, GIVING POTENTIAL DIFFERENCE IN C. G. S. UNITS.

Thus taking copper and iron we find at the temperature 0° C. (32° F.) a difference of one degree C. (1.8° F.) in their junctions will produce a potential difference of 15.98 micro volts, while at 274.5° C. (526.1° F.) the lines cross, and zero difference of potential is indicated. Taking the lead line on the same diagram it crosses the iron line a little above 350° C. (662° F.), indicating that if one junction is heated slightly above and the other is heated slightly below this temperature no potential difference will be produced. Lead and copper lines, on the other hand, diverge more and more as the temperature rises.

533 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Inversion. The thermo-electric relations of two conductors vary at different temperatures. Sometimes at a definite point they have no electro-motive force and after passing this point the positive plate becomes a negative one and vice versa. This is inversion, or reversal. (See Thermo-electric Diagram.)

Synonym-- Thermo-electric Reversal.

Thermo-electricity. Electric energy, electro-motive force or electrification produced from heat energy by direct conversion. It is generally produced in a circuit composed of two electric conductors of unlike material, which circuit must possess at least two junctions of the unlike substances. By heating one of these to a higher temperature than that of the other, or by maintaining one junction at a different temperature from that of the other a potential difference is created accompanied by an electric current.

In many cases differential application of heat to an identical material will develop potential difference. This effect, the converse of the Thomson effect, is not used to produce currents, as in a closed circuit the potential differences due to differential heating would neutralize each other.

Thermo-electric Junction. A junction between two dissimilar conductors, which when heated or cooled so as to establish a differential temperature, as referred to the temperature of the other junction, produces potential difference and an electric current.

Thermo-electric Pile, Differential. A thermo-electric pile arranged to have opposite faces subjected to different sources of heat to determine the identity or difference of temperature of the two sources of heat. It corresponds in use to a differential air thermometer.

Thermo-electric Power. The coefficient which, multiplying the difference of temperature of the ends of a thermo-electric couple, gives the potential difference, expressed in micro-volts. It has always to be assigned to a mean or average temperature of the junctions, because the potential difference due to a fixed difference of temperature between two metals varies with the average temperature of the two junctions. (See Thermo-electric Diagram.)

For bismuth and antimony at 19.5° C. (67.1° F.) it is 103 microvolts per degree Centigrade (1.8° F.). This means that if one junction is heated to 19° C. and the other to 20° C. (66.2° F. and 68.0° F.) a potential difference of 103 micro-volts will be produced.

The potential difference is approximately proportional to the difference of temperature of the two junctions if such difference is small. Hence for large differences of potential the thermo-electric power coefficient does not apply.

As a differential function it is thus deduced by Sir William Thomson, for expressing the E. M. F. in a thermo-electric circuit: If a circuit is formed of two metals with the junctions at indefinitely near temperatures, t and t + dt, and dE is the E. M. F. of the circuit, then the differential coefficient dE/dt is called the thermo-electric power of the two metals for the temperature t.

534 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Series. The arrangement of possible thermoelectric elements, q. v., in a table in the order of their relative polarity. Bismuth and antimony form a couple in which when their junction is heated the bismuth acts as the positive or negatively charged element and antimony as the negative or positively charged. Between these two extremes according to Seebeck the series runs as follows:

Antimony, Silver, Copper,
Arsenic, Gold, Platinum,
Iron, Molybdenum, Palladium,
Steel, Tin, Cobalt,
Cadmium, Lead, Nickel,
Tungsten, Mercury, Bismuth.
Zinc, Manganese,

A differential temperature of 1° C. (1.8° F.) in a bismuth-antimony couple maintains a potential difference of 103 micro-volts.

Matthiessen gives a different series; it is arranged in two columns; the
first column has positive coefficients annexed the second has negative.
On subtracting the greater one from the lesser, which, if the two
elements are in different columns, of course amounts to adding after
changing the negative sign, the relative potential difference due to the
combination is obtained.
+ -
Bismuth 25 Gas Coke 0.1
Cobalt 9 Zinc 0.2
Potassium 5.5 Cadmium 0.3
Nickel 5 Strontium 2.0
Sodium 3. Arsenic 3.8
Lead 1.03 Iron 5.2
Tin 1 Red Phosphorous 9.6
Copper 1 Antimony 9.8
Silver 1 Tellurium 179.9
Platinum 0.7 Selenium 290

Thus the relative E. M. F. of a bismuth-nickel couple, as both are in the + column, would be 25 - 5 = 20; that of a cobalt-iron couple, one being in the + column the other in the - column, would be 9 + 5.2 = 14.2. Alloys are not always intermediate to their constituents, and small amounts of impurities affect the results largely. This may account for the discrepancies of different observers. Other compounds could be introduced into the series.

Artificial silver sulphide has been used by Becquerel in a thermo-electric battery.

535 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Thermometer. A species of differential thermometer. It consists of two thermo-electric junctions connected in opposition with a galvanometer in the circuit. Any inequality of temperature in the two ends or junctions produces a current shown by the galvanometer. It may be used to determine the temperature of a distant place, one of the junctions being located there and the other being under control of the operator. If the latter junction is heated until no current is produced its temperature is evidently equal to that of the distant couple or junction. The heating may be done with hot water or mercury, or other melted metal. The temperature of the water, or other substance, gives the temperature of the distant place.

Thermolysis. Decomposition by heat; dissociation. All compound bodies are decomposable by heat if it is intense enough. Hence at very elevated temperatures there can be no combustion.

Synonym--Dissociation.

Thermometer. An instrument for indicating the intensity of heat. Three scales of degrees of heat are used in practise, the Fahrenheit, Réamur, and Centigrade, each of which is described under its own title. (See Zero, Thermometric-Zero, Absolute.) The ordinary thermometer depends on the expansion of mercury; in some cases alcohol is used. Besides these the compound bar principle as used in the thermostat (see Thermostat, Electric) is employed.

Thermometer, Electric. (a) A thermometer whose indications are due to the change of resistance in conductors with change of temperature. Two exactly similar resistance coils maybe electrically balanced against each other. On exposing one to a source of heat, its resistance will change and it will disturb the balance. The balance is restored by heating the other coil in a vessel of water when the temperature of the water gives the temperature of both coils. The coils are enclosed in water-tight metallic cases.

Synonym--Electric Resistance Thermometer.

(b) A differential thermometer may be made by connecting with a pair of conductors, two thermo-electric couples in opposition to each other, and including a galvanometer in series. On heating the junction of one couple more than that of the other a current at once goes through the galvanometer.

(c) (See Thermometer, Kinnersley's.)

Synonym--Thermo-electrometer.

536 STANDARD ELECTRICAL DICTIONARY.

Fig. 334. KINNERSLEY'S THERMOMETER.

Thermometer, Kinnersley's. A thermo-electrometer. A large glass tube is mounted on a standard and communicates with a small tube parallel to it. Water is poured in so as to rise in the small tube. Two wires terminating in bulbs enter the large tube by its top and bottom. The upper wire can be adjusted by moving up and down through a stuffing box. On discharging a Leyden jar through the space between the knobs on the two wires the water for a moment rises in the small tube. There is little or no accuracy in the instrument. It is allied to the electric mortar (see Mortar, Electric) as a demonstrative apparatus.

Synonyms--Electric Thermometer--Thermo-electrometer.

Thermo-multiplier. A thermo-electric battery including a number of couples. The term is generally applied to a small battery with its similar junctions facing in one direction and used for repeating Melloni's experiments on radiant energy, or so-called radiant heat.

537 STANDARD ELECTRICAL DICTIONARY.

Thermophone. An apparatus for reproducing sounds telephonically by the agency of heat; a receiving telephone actuated by heat. Thus a wire may be attached to the centre of a diaphragm and kept in tension therefrom, and the transmitting telephone current may be caused to pass through it. The wire changes in temperature and consequently in length with the pulses of current going through it and vibrates the diaphragm, reproducing the sound. It is to be distinguished from the thermo-electric telephone which involves the action of potential difference produced by thermo-electric action.

Thermostat, Electric. A thermostat or apparatus, similar to a thermometer in some cases, for closing an electric circuit when heated. It is used in connection with automatic fire alarms to give warning of fire. For this use a temperature of 52° C. (125° F.) is an approved one for setting one at, to complete the circuit. It is also applied to regulation of temperature, as in incubators.

(a) One kind of thermostat consists of a compound bar wound into a spiral and fastened at one end, to which a terminal of a circuit is connected. The bar may be made of two strips of brass and iron riveted together, and wound into a spiral. When such a bar is submitted to changes of temperature it bends in different directions, because brass expands and contracts more under changes of temperature than does iron. A contact point, to which the other terminal is connected, is arranged to make contact with the spiral at any desired degree of temperature, thus closing an electric circuit and ringing a bell, opening or closing a damper, or doing anything else to notify an attendant or to directly change the temperature.

If the brass forms the outside of the spiral, increase of temperature makes the bending of the spiral bring the coils still closer. If the brass forms the inside, increase of temperature makes the spiral tend to become less close. As shown in the cut, the brass should lie along the inside of the spiral.

Sometimes a straight compound bar is used, one of whose ends is fastened and the other is free. As the temperature changes such a bar curves more or less, its free end moving to and fro. Two contact screws are provided, one on each side of its free end. If the temperature falls it makes contact with one of these; if the temperature rises, it makes contact with the other. Thus it may close one of two circuits, one for a fall and the other for a rise in temperature.

It is well to introduce a third bar between the brass and iron ones, made of some material of intermediate coefficient of expansion.

(b) Another kind of thermostat comprises a vessel of air or other gas, which, expanding by heat, actuates a piston or other device and closes an electric circuit. Synonym--Electro-pneumatic Thermostat.

(c) Another form utilizes the expansion of mercury. The mercury is made part of an open electric circuit. As it expands it comes in contact with the other terminal of the circuit, thus completing it, when the current gives an alarm or does as is provided for in the apparatus employed.

Thermostats may be worked on either open or closed circuits; normally the circuit may be open as described and may close on rise of temperature, or it may be normally closed and open as the temperature rises.

Fig. 335. ELECTRIC THERMOSTAT.

538 STANDARD ELECTRICAL DICTIONARY.

Thomson Effect. In an unequally heated conductor the differential heating is either increased as in iron, or diminished as in copper by a current. In lead the phenomenon does not occur. It is termed the Thomson effect. It is intimately related to the Peltier effect.

In a thermo-electric couple a heated junction is the source of electro-motive force, if heated more than other parts of the circuit. The current in a copper-iron junction flows from the copper to the iron across the heated junction. A hot section of an iron conductor next to a cold section of the same is a source of thermoelectricity, in the sense that the hot section is negative to the colder. A current passing from the hot to the cold iron travels against rising potentials, and cools the iron in the cooler parts. As it passes to the hotter parts it travels against falling potentials and hence heats the iron in these parts. In this way a current intensifies differential heating in an iron conductor.

In copper the reverse obtains. In it the thermo-electric relations of hot and cold copper are the reverse of those of iron, and a current tends to bring all parts of a differentially heated copper conductor to an identical temperature.

As a current travels in iron from hot to cold it absorbs heat; in copper traveling from cold to hot it absorbs heat.

The convection of heat by a current of electricity in unequally heated iron is negative, for it is opposed to that convection of heat which would be brought about by the flow of water through an unequally heated tube. In copper, on the other hand, the electric convection of heat is positive. (Daniell.)

The above effects of the electric current upon an unequally heated conductor are termed the Thomson effects. In iron, at low red heat, they are reversed and are probably again reversed at higher temperatures.

539 STANDARD ELECTRICAL DICTIONARY.

Three Wire System. A system of distribution of electric current for multiple arc or constant potential service. It is the invention of Thomas A. Edison.

It includes three main wires which start from the central station or generating plant, and ramify with corresponding reduction in size, everywhere through the district or building to be lighted. As ordinarily carried out when dynamos are used, the dynamos are arranged in groups of two. One lateral lead starts from the negative binding post of one dynamo. The positive terminal of this dynamo connects to the negative of the other. Between the two dynamos the central or neutral lead is connected. The other lateral lead starts from the positive binding post of the second dynamo.

The lamps or other appliances are calculated for the potential difference of a single dynamo. They are arranged between the neutral wire and the laterals, giving as even a disposition as possible to the two laterals.

Fig. 336. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE.

If evenly arranged and all burning or using current, no current goes through the neutral wire. If all the lamps situated on one lateral are on open circuit all the current goes through the neutral wire. In other cases the neutral wire receives the excess of current only.

The advantages of the system are that it uses smaller wire than the two wire system for lamps of the same voltage. If lamps of double the voltage were used the two wire system would be most economical.

540 STANDARD ELECTRICAL DICTIONARY.

Four wire and five wire systems have been more or less used, based on identical considerations, and involving in each case the coupling of three or of four dynamos respectively, or else employing a dynamo with special armature connections to give the requisite three-fold or four-fold division of total potential. In the five wire system the total voltage is four times that of a single lamp, the lamps are arranged four in series across the leads and the central wire is the only one that can be considered a neutral wire. When lamps are burning entirely from three side-leads they constitute a sort of three wire system by themselves, and their central wire may for the time be a neutral wire.

In some of the three wire mains, especially in the larger sizes, the neutral wire is made of much smaller section than that of a lateral conductor, because in extensive districts it is practically impossible that the current should be concentrated in the neutral wire.

Throw. In a galvanometer the instantaneous deflection of the needle when the contact or closing of the circuit is instantaneous, or when the discharge is completed before the needle begins to move. The throw of the needle is the datum sought when the ballistic galvanometer is used.

Synonym--Elongation.

Throw-back Indicator. A drop annunciator, whose shutter or drop is electrically replaced.

Thrust-bearings. Bearings to support the end-thrust or push of a shaft. In disc armatures where the field-magnets attract the armatures in the direction of their axis of rotation, thrust-bearings have to be provided. In ordinary cylinder or drum armatures end-thrust is not applied, as a little end motion to and fro is considered advantageous as causing more even wear of the commutator surface.

Thunder. The violent report which, as we hear it, succeeds the lightning flash in stormy weather. It is really produced simultaneously with the lightning and is supposed to arise from disturbance of the air by the discharge. The rolling noise has been attributed to successive reflections between clouds and earth, and to series of discharges reaching the ear from different distances and through air of varying density. The subject is obscure. By timing the interval from lightning flash to the report of the thunder an approximate estimate of the distance of the seat of discharge can be made. The first sound of the thunder should be timed. An almost concurrence of thunder and lightning indicates immediate proximity of the discharge.

[Transcriber's note: The speed of sound at sea level is about 5 seconds per mile.]

Ticker. A colloquial name for a stock or market report automatic printing telegraph, which prints its quotations and messages on a long tape.

541 STANDARD ELECTRICAL DICTIONARY.

Time Constant. (a) When current is first turned into a circuit of considerable self-induction it is resisted rather by the inductance than by the resistance. It is governed by the ratio of resistance and self-induction and this factor represents the time which it takes for the current to reach a definite fraction of its final strength. This fraction is (2.7183 - 1)/2.7183 or 0.63. 2.7183 is the base of the Napierian system of logarithms. Thus if in any circuit we divide the inductance in henries by the resistance in ohms, the ratio gives the time-constant of the circuit, or it expresses the time which it will take for the current to reach 0.63 of its final value.

(b) In a static condenser the time required for the charge to fall to 1/2.7183th part of its original value.

Time Cut-outs. Cut-outs which automatically cut storage batteries out of the charging circuit when they are sufficiently charged.

Time-fall. In a secondary battery the decrease with use of electromotive force maintained by a primary or secondary battery. As the battery becomes spent its voltage falls. The conditions of the fall are represented by its discharging curve. (See Curve, Discharging.)

Time-reaction. A term in electro-therapeutics; the period of time occupied in the passage of the effects of an electric current from nerve to muscle.

Time-rise. In a secondary battery the increase of electromotive force produced during the charging process. Its rate and conditions are graphically shown in the charging curve. (See Curve, Charging.)

Tin. A metal; one of the elements; symbol, Sn; atomic weight, 117.8; equivalent, 58.9 and 29.5; valency, 2 and 4; specific gravity, 7.3. It is a conductor of electricity.

Relative resistance, compressed, (Silver = 1) 8.784
Specific resistance at 0° C. (32° F.), 13.21 microhms.
Resistance of a wire at 0° C. (32° F.),
(a) 1 foot long, weighing 1 grain, 1.380 ohms.
(b) 1 foot long, 1/1000 inch thick, 79.47 "
(c) 1 meter long, weighing 1 gram, .9632 "
(d) 1 meter long, 1 millimeter thick, .1682 "
Resistance of a 1 inch cube at 0° C. (32° F.), 5.202 microhms.
Percentage of variation in resistance
per degree C. (1.8° F.), at about 20° C. (68° F.), .0365
Electro-chemical equivalent (hydrogen = .0105), .619 mgs.
.310 "

542 STANDARD ELECTRICAL DICTIONARY.

Tinnitus, Telephone. A nervous affection of the ear, of the order of professional cramp; it is attributed to too much use of the telephone.

Tin Sounders. A recent addition to the single needle telegraph. (See Telegraph, Single Needle.) It consists of small tin plates, cut and bent, and so fitted in pairs to the instrument, that the needle as deflected strikes one or the other on its right and left hand movements. The sounders can be made to give sufficiently distinctive sounds to make sound-reading, q. v., possible. Commercial tin plate, which is really tinned iron, seems to give the best results.

Fig. 337. TIN SOUNDERS.

Tissandier's Solution.
A solution for bichromate batteries. It is composed as follows:
Water, 100 parts by weight
potassium bichromate, 16 parts
66° sulphuric acid, 37 parts.

Tongue of Polarized Relay. The German silver extension of the vibrating or oscillating member of a polarized relay, corresponding to the armature of an ordinary relay.

Tongue of Polarized Relay, Bias of. In a Siemens' polarized relay the pole pieces are adjustable so that they may be brought nearer to or withdrawn from the tongue. One of the poles is adjusted so as to be nearer the tongue. This one-sided adjustment is the bias. Its effect is that when the relay is unexcited this pole attracts the armature so that it normally is drawn towards it. This ensures the normal contact of the tongue either with the contact point, or with the insulated stop piece or adjustment screw. Without bias the armature remains in contact with or drawn towards whichever pole it was last attracted to. In its usual use a bias is given it.

Top, Magnetic. A toy illustrating magnetic attraction. It consists of a disc or body of lead or other material, through which a magnetized steel spindle pointed at its lower end is thrust. A number of short pieces of iron wire are used with it. It is spun like an ordinary top upon the point of the spindle and one of the pieces of iron wire is laid by the side of its point. As it turns the magnetic adherence causes the piece of wire to be carried along in one direction by the rotation of the spindle, until the end is reached, when it goes over to the other side of the spindle and travels back again.

By using bent pieces of wire of various shapes the most curious effects are produced. Circles and S shaped pieces give good effects. To increase the mysterious effect covered iron wire (bonnet wire) may be employed.

Fig. 338. MAGNETIC TOP.

543 STANDARD ELECTRICAL DICTIONARY.

Torpedo, Electric. (a) A fish, the Raia Torpedo, which possesses the power of giving electric shocks. (See Ray, Electric.)

(b) An instrument of war; a torpedo whose operations include electrical discharge or other electric function or factor of operation.

Torpedo, Sims-Edison. A torpedo driven by an electric motor, and also steered by electricity. Its motions are all controlled from the shore. The torpedo proper is carried some distance below the surface of the water by a vessel immediately above it, from which it is suspended by two rigid bars. In the torpedo is a cable reel on which the conducting cable is disposed. An electric motor and controlling gear are also contained within the torpedo. In its front the explosive is placed. It is driven by a screw propeller actuated by the electric motor. As it moves it pays out cable so that it has no cable to draw after it through the water, the cable lying stationary in the water behind it. This avoids frictional resistance to its motion. The maintenance of the torpedo at a proper depth is one of the advantages of the system.

544 STANDARD ELECTRICAL DICTIONARY.

Torque. A force tending to produce torsion around an axis. An example is the pulling or turning moment of an armature of an electric motor upon its shaft. It is often expressed as pounds of pull excited at the end of a lever arm one foot long.

The expression is due to Prof. James Thompson, then of the University of Glasgow.

"Just as the Newtonian definition of force is that which produces or tends to produce motion (along a line), so torque may be defined as that which produces or tends to produce torsion (around an axis). It is better to use a term which treats this action as a single definite entity than to use terms like 'couple' and 'moment,' which suggest more complex ideas." (S. P. Thompson.)

A force, acting with radius r gives a torque equal to f X r ; f and r may be expressed in any units. S. P. Thompson gives the following equivalents :

To reduce
dyne-centimeters to gram centimeters, divide by 981
dyne-centimeters to meter-kilograms divide by 981E5
dyne-centimeter, to pound-feet divide by 13.56E6
pound-feet to meter-kilograms divide by 7.23

In each of these compound units the first unit is the force and the second unit is the radius or lever arm of the torque.

Synonyms--Turning Moment--Moment of Couple--Axial Couple--Angular Force--Axial Force.

Torsion Balance, Coulomb's. Originally an apparatus in which electrostatic attraction or repulsion is measured against the torsion of a filament, often of silk-worm cocoon fibre. It consists in one form of a cylindrical glass vessel in which a light shellac needle is suspended horizontally by a fibre. This needle carries at one end a gilded disc or sphere and is suspended by a fine wire, or filament. A proof plane, q. v., is excited by touching it to the body under trial; it is then inserted in the case. The disc on the needle is first attracted and then repelled. The position finally taken by the needle is noted. The force of torsion thus produced is determined by twisting the filament by the torsion head on the top of the apparatus so as to move the needle a certain distance towards the proof plane. The more the torsion-head has to be turned to carry the needle through a specified arc the greater is the torsion effected or the greater is the repulsion exerted, The torsional force of a wire is proportional to the angle of torsion; this gives the basis for the measurement.

With magnetic needle it is used to measure magnetic repulsion and attraction. The best material for the filament is quartz, but the instrument is not very much used.

Torsion Galvanometer. A galvanometer in which the torsion required to bring the index back to zero, when the current tends to displace it, is made the measure of the current strength or of the electro-motive force. It involves the use of a torsion head, q. v., or its equivalent.

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Torsion Head. The handle and disc from whose undersurface the filament depends to which the needle or magnet is attached. It is turned to measure the torsional effect, the edge of the disc being marked or graduated so as to give the angle of deflection required to overcome the effect of the torque of the needle.

Torsion Suspension. Suspension by one or more wires, fibres, or ribands, involving the restitutive force of torsion. Thus fibre suspension, q. v., is a variety of torsion suspension.

Often a single riband of steel stretched horizontally and secured at both ends is used, the suspended object, e. g., a balance beam, being attached at its own centre to the centre of the stretched riband. Quite sensitive balances are constructed on this principle. It is peculiarly available where an electric current is to be transmitted, as absolute contact is secured, as in William Thomson's ampere balances.

Touch. A term applied to methods of magnetization, as "single touch," "double touch," or "separate touch," indicating how the poles of the inducing magnet or magnets are applied to the bar to be magnetized. Under the titles of Magnetization the different methods are described.

Tourmaline. A mineral; a subsilicate; characterized by the presence of boric trioxide, which replaces aluminum oxide. It is notable for possessing pyro-electric properties. (See Pyro-electricity.)

Tower, Electric. The tower used in the tower system, q. v., of arc light illumination.

Tower System. In electric lighting the system of lighting extended areas by powerful arc lamps placed on high towers, generally of iron or steel frame-work. The lights are thus maintained at a high elevation, giving greater uniformity of illumination than if they were lower, but at the expense of considerable light which is lost. Sometimes wooden masts are employed instead of towers.

The principle involved is that the intensity of light at any place given by a source of illumination varies with the square of its distance from the place in question. Hence in using strong arc lights it is an object to have the distances of all parts of the area illuminated at as nearly uniform distances from the light as possible. An approximation to uniformity is secured by placing the lamps at a very high elevation.

546 STANDARD ELECTRICAL DICTIONARY.

Transformer. In alternate current lighting the induction coil by which the primary current with high initial electro-motive force is caused to produce a secondary current with low initial electromotive force.

A typical transformer consists of a core of thin iron sheets. The primary is of comparatively thin wire and often of ten or more times as many turns as the secondary. The latter is of thicker wire. Where the ratio of 10 to 1 as regards number of turns in the primary and secondary obtains, the initial E. M. F. of the secondary is one-tenth that of the primary circuit.

The cores are laminated, as described, to avoid the formation of Foucault currents.

The counter-electro-motive force of the transformer when the secondary circuit is open, prevents any but the slightest current from passing through the primary. In proportion as the secondary is closed and its resistance diminished, as by lighting more lamps in parallel, the counter-electro-motive force of the transformer falls and more current passes through the primary.

Fig. 339. FERRANTI'S TRANSFORMER.

The economy of the apparatus is in the fact that counter-electromotive force reduces current through a conductor without absorbing any energy. A resistance coil cuts down a current, but absorbs energy equal to the current multiplied by the potential difference between the terminals of the coil. This electric energy is converted into heat energy and is wasted. But the counter-electromotive force of a transformer is exerted to reduce current without production of heat and with little waste of energy. This is one of the advantages of the alternating current system of distribution of electric energy.

The object of a transformer being to secure safety to the person or to life by the separation of the high potential primary or street circuit, and the low potential house circuit, any contact of the two circuits in the converter is a source of danger. Special care should be taken to ensure absence of leakage, as it is termed. Mica or other insulation is sometimes employed to prevent the wires from coming in contact by piercing or sparking with the core and with each other.

547 STANDARD ELECTRICAL DICTIONARY.

Transformer, Commuting. A type of continuous current transformer, resembling a dynamo with armature and field both stationary, but with revolving commutator, by which the magnetic polarity of a double wound armature is made to rotate. This secures the desired action, of a change or lowering of potential.

Transformer, Continuous Alternating. An apparatus for transforming a continuous into an alternating current or the reverse. The combination of a continuous current dynamo with an alternating current one is sometimes employed. It is a form of motor dynamo.

Another type is a regular dynamo with ordinary commutator and with, in addition thereto, two, three or four contact rings, connecting to as many symmetrically disposed points in the winding of the armature. This will give out or receive alternating currents of two, three or four phases according to the number of collecting rings. One winding serves for both alternating and continuous currents.

Transformer, Continuous Current. A machine of the dynamo type for changing the potential of a circuit. In one form two armatures are mounted on one shaft in a single field or in separate fields; one is a motor armature driven by the original current; the other generates the new current. This is a motor dynamo. In 1874 Gramme constructed a machine with ring armature with two windings, of coarse and fine wire respectively, and with independent commutators. Such dynamo could transform currents up or down.

Continuous current transformers have attained an efficiency of 83 per cent. at full load, and of 75 per cent. at half load. Owing to the balancing of the self-inductions of the two windings these machines do not spark. As the driven and driving parts are contained in one rotating part their friction is very slight.

Transformer, Core. A transformer wound upon an enclosed core, such as the hedgehog transformer (see Transformer, Hedgehog), or common induction coil.

548 STANDARD ELECTRICAL DICTIONARY.

Transformer, Hedgehog. An induction coil transformer whose iron core is composed of a bundle of iron wires, which after the wire windings are in place have their ends spread out to reduce to some extent the reluctance of the circuit, which at the best is high, as the air acts as the return circuit.

This transformer has a low degree of hysteresis; and its efficiency for very small loads or for no load is superior to that of the closed magnetic circuit transformer.

Fig. 340. SWINBURNE'S HEDGEHOG TRANSFORMER.

Transformer, Multiple. A transformer connected in parallel with others between the two leads of the primary circuit. The term refers to the connection only and not to any peculiarity of the transformer itself.

Transformer, Oil. A transformer with oil insulation. The advantage of this insulation is that if pierced it at once closes, so that no permanent injury ensues. It is a self-healing form of insulation.

Transformer, Series. Transformers connected in series upon the primary circuits. The term, like "multiple transformers," only applies to the connection, not to the transformer. Series transformers are but little used.

Transformer, Shell. A transformer with its iron core entirely outside of and enclosing the primary and secondary winding. It may be made by the use of outer iron wire windings as core.

Transformer, Welding. The transformer used for electric welding. (See Welding, Electric.) It is a transformer with very long primary and exceedingly short and thick secondary. It is used with the alternating current in the primary, and produces in the secondary circuit which includes the bars to be welded a very low potential difference.

Owing to the very low resistance of the secondary circuit this low electro-motive force produces a very strong current, which develops the requisite heat. The same type of transformer is used for brazing and similar purposes.

549 STANDARD ELECTRICAL DICTIONARY.

Transmitter. In general electric phraseology, any instrument which produces signals to be transmitted through a line or circuit is a transmitter. Thus the Morse key in telegraphy or the Blake transmitter in telephony are examples of such.

Transmitter, Carbon. A form of microphone used as a telephone transmitter. (See Carbon Telephone.)

Transposing. A method of laying metallic circuits for telephoning. The wires at short intervals are crossed so that alternate sections lie on opposite sides of each other. It is done to avoid induction.

Transverse Electro-motive Force. Electro-motive force in a substance in which electric displacement is taking place, produced by a magnetic field. It is sometimes assigned as the cause of the Hall effect, q. v.

Trimmer, Brush. A shears for cutting off evenly and squarely the ends of copper dynamo brushes. The brushes when uneven from wear are removed from the brush holders, and their ends are sheared off in the trimmer.

Trolley. A grooved metallic pulley or set of pulleys which runs along an active wire of a circuit, a lead from which trolley goes to earth or connects with another wire, so that the trolley takes current generally for operating a street car motor placed upon the circuit leading from it; a rolling contact with an electric lead.

Trolleys are principally used on electric railroads, and are now universally of the sub-wire system, being at the end of a pole which is inclined backward and forced upward by springs, so as to press the trolley against the bottom of the wire. Thus the trolley does not increase the sagging of the wire, but tends to push it up a little in its passage.

Trolley, Double. A trolley with two rollers or grooved wheels, placed side by side, and running on two parallel leads of wire. It is adapted to systems employing through metallic trolley lines with the motors in multiple arc, connecting or across the two leads.

Trolley Section. An unbroken or continuous section of trolley wire.

Trouvé's Solution. An acid exciting and depolarizing solution for a zinc-carbon battery. Its formula is as follows: Water, 80 parts; pulverized potassium bichromate, 12 parts; concentrated sulphuric acid, 36 parts; all parts by weight. The pulverized potassium bichromate is added to the water, and the acid is added slowly with constant stirring. As much as 25 parts potassium bichromate may be added to 100 parts of water. The heating produced by the acid and water dissolves nearly all the potassium salt. Use cold.

550 STANDARD ELECTRICAL DICTIONARY.

True Contact Force. A species of electro-motive force whose existence is supposed to be proved by the Peltier effect. The lowering in temperature of a contact of dissimilar metals is attributed to a force that helps the current on its way if in the direction of thermo-current proper to the junction and opposing it if in the reverse. The true contact force is taken to explain this phenomenon; thermo-electric force cannot, as there is no heat or cold applied to the junction.

Trumpet, Electric. An apparatus consisting of a vibrating tongue, kept in motion by electricity as in the buzzer, q. v., placed in the small end of a trumpet-shaped tube.

Trunking Switchboard. A telephone switchboard arranged in sections, which sections are connected by trunk lines, through which trunk lines the desired connections are made.

Trunk Lines. In telephone distribution systems, the lines connecting different stations, or different sections of a switch-board and used by anyone requiring such connections; one trunk line answers for a number of subscribers.

Tube, Electric. A tube of glass around which is pasted a series of tinfoil circles, diamonds, or little squares, or other form of interrupted conductor. The pieces generally are placed in the line of a spiral. When a static discharge of electricity takes place along the conductor a row of bright sparks is produced at the breaks in the conductor. These by reflection are multiplied apparently, and a beautiful effect of intersecting or crossing spirals of sparks is presented.

The experiment is in line with the luminous pane and lightning jar, and is used merely as a demonstration, or lecture experiment.

Synonym--Luminous Tube.

Tubular Braid. A braid woven of tissue or worsted, and tubular or hollow. Its object is to provide a covering which can be drawn over joints in covered wires. In making the joint the ends of the wires are necessarily bared, and a short piece of tubular braid is used for covering them. It is drawn by hand over the joint.

Turns. An expression applied to the convolutions of wire in a solenoid, electro-magnet, or other apparatus or construction of that kind. A turn indicates a complete encircling of the core or axis of the object. Thus a wire wound five times around a bar gives five turns.

While this is its primary meaning the term if compounded may refer to virtual turns. Thus an ampere-turn means one ampere passing through one turn. But ten ampere-turns may mean ten amperes passing through ten turns, five amperes passing through two turns, and so on. This use is analogous to a dimension of length in a compound word, as foot-pound.

[Transcriber's note: "But ten ampere-turns may mean ten amperes passing through ONE turn or one ampere through ten turns, and so on."]

There may be a number of kinds of turns qualified by descriptive adjectives, as series-turns, the turns of wire in a series circuit of a compound dynamo. In the same way there are shunt-turns. If series ampere-turns or shunt ampere-turns are meant the word ampere should be included.

551 STANDARD ELECTRICAL DICTIONARY.

Turns, Dead, of a Dynamo. The rotations of a dynamo armature while it is building itself up or exciting itself. The expression is a bad one, as it is likely to be confounded with the dead turns of armature wire.

Turns, Primary Ampere-. The ampere-turns in a primary circuit of an induction coil or transformer. In an electric welding transformer, or in the transformer used in the alternating current system, where efficiency is an important element, the ampere-turns in primary and secondary for an efficiency of 100 per cent. should be equal. In the case of an experimental induction coil other considerations outweigh that of mere efficiency. Insulation, including security from piercing, and the production of as long a spark as possible, are, in these cases, the controlling consideration.

[Transcriber's note: A 100 per cent efficient transformer is impossible, but over 99 per cent is common. At room temperature there is always some lost flux, eddy currents and resistive losses.]

Turns, Secondary Ampere-. The ampere-turns on the secondary circuit of an induction coil or transformer. These depend on the path provided for the current. If of negligible inductance, such as a number of incandescent lamps would provide, the ampere-turns should be equal to those of the primary coil. (See Turns, Primary Ampere.)

Typewriter, Electric. A typewriter in which the work of printing or of pressing the type faces against the paper, or printing ribbon, is done by electro-magnetic attraction. The keys close electric circuits, throwing the electro-magnetic action into play. This involves the use of electricity for what is ordinarily only a mechanical process. The strength of the impression, however, is independent of the touch of the operator. It has not come into very extensive use.

[Transcriber's note: IBM introduced widely used electric typewriters in 1935.]

Ultra-gaseous Matter. Gas so rarefied that its molecules do not collide or very rarely do so.

Experiments of very striking nature have been devised by Crookes and others to illustrate the peculiar phenomena that this matter presents. The general lines of this work are similar to the methods used in Geissler tube experiments, except that the vacua used are very much higher.

When the vacuum is increased so that but one-millionth of the original gas is left the radiant state is reached. The molecules in their kinetic movements beat back and forth in straight lines without colliding, or with very rare collisions. Their motions can be guided and rendered visible by electrification. A tube or small glass bulb with platinum electrodes sealed in it, is exhausted to the requisite degree and is hermetically sealed by melting the glass. The electrodes are connected to the terminals of an induction coil or other source of high tension electrification. The molecules which come in contact with a negatively electrified pole are repelled from it in directions normal to its surface. They produce different phosphorescent or luminous effects in their mutual collisions.

Thus if they are made to impinge upon glass, diamond or ruby, intense phosphorescence is produced. A piece of platinum subjected to molecular bombardment is brought to white heat. A movable body can be made to move under their effects. Two streams proceeding from one negative pole repel each other. The stream of molecules can be drawn out of their course by a magnet.

The experiments are all done on a small scale in tubes and bulbs, resembling to a certain extent Geissler tubes.

[Transcriber's note: These effects are caused by plasma--ionized gas and electrons.]

552 STANDARD ELECTRICAL DICTIONARY.

Unbuilding. The loss of its charge or excitation by a self-exciting dynamo. It is the reverse of building-up. The latter indicates the exciting of the field by the action of the machine itself; the former the spontaneous loss of charge on open circuit or from other cause.

Underground Conductor. An electric conductor insulated and placed under the surface of the earth, as distinguished from aerial conductors.

Underground Electric Subway. A subway for the enclosing of electric telegraph and other conductors under the surface, generally in the line of streets, to do away with telegraph poles and aerial lines of wire. Many systems have been devised. The general type includes tubes called ducts in sets, called conduits, bedded in concrete or otherwise protected. Every two or three hundred feet the sets lead into a cistern-like cavity called a manhole. The insulated wires or cables, generally sheathed with a lead alloy are introduced into the tubes through the man-holes. A rope is first fed through the tube. To do this short rods which screw together are generally employed. One by one they are introduced, and each end one is screwed to the series of rods already in the duct. When the end of the duct is reached the rope is fastened to the last rod, and the rods are then drawn through, unscrewed one by one and removed, the rope following them. By means of the rope a windlass or capstan may be applied to draw the cable into the duct. At least at every second man-hole the cables have to be spliced.