The Standard Electrical Dictionary Part 162

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 a.s.signed 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 princ.i.p.ally 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 pa.s.sage.

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.

Trouv?'s Solution.

An acid exciting and depolarizing solution for a zinc-carbon battery.

Its formula is as follows: Water, 80 parts; pulverized pota.s.sium bichromate, 12 parts; concentrated sulphuric acid, 36 parts; all parts by weight. The pulverized pota.s.sium bichromate is added to the water, and the acid is added slowly with constant stirring. As much as 25 parts pota.s.sium bichromate may be added to 100 parts of water. The heating produced by the acid and water dissolves nearly all the pota.s.sium 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 gla.s.s 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 pa.s.sing through one turn. But ten ampere-turns may mean ten amperes pa.s.sing through ten turns, five amperes pa.s.sing through two turns, and so on. This use is a.n.a.logous to a dimension of length in a compound word, as foot-pound.

[Transcriber's note: "But ten ampere-turns may mean ten amperes pa.s.sing 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.]