The Standard Electrical Dictionary Part 33

Circuit Breaker, Pendulum.

A circuit breaker in which a pendulum in its swing makes and breaks a contact. It may be kept in motion by clockwork, or by an electro-magnet, attracting intermittently an armature attached to its rod, the magnet circuit being opened and closed by the pendulum or circuit breaker itself. A mercury contact may be used with it.

Fig. 88. PENDULUM CIRCUIT BREAKER.

122 STANDARD ELECTRICAL DICTIONARY.

Circuit Breaker, Tuning Fork.

A circuit breaker in which a tuning fork makes and breaks the circuit.

Each vibration of one of the p.r.o.ngs in one direction makes a contact, and the reverse vibration breaks a contact. The adjustment is necessarily delicate, owing to the limited amplitude of the motion of the fork. The fork is kept in vibration sometimes by an electro-magnet, which is excited as the circuit is closed by the fork. One leg of the fork acts as the armature of the magnet, and is attracted according to its own natural period.

Circuit Breaker, Wheel.

A toothed wheel with a spring bearing against its teeth. One terminal of a circuit connects with the wheel through its axle, the other connects with the spring. When the wheel is turned the circuit is opened and closed once for each tooth. The interstices between teeth on such a wheel may be filled with insulating material, giving a cylindrical surface for the contact spring to rub on.

Fig. 89--TOOTHED WHEEL CIRCUIT BREAKER.

Circuit, Closed.

A circuit whose electric continuity is complete; to make an open circuit complete by closing a switch or otherwise is to close, complete, or make a circuit.

Synonyms--Completed Circuit--Made Circuit.

Circuit, Compound.

A circuit characterized by compounding of generating or receiving devices, as including several separate batteries, or several motors, or other receiving devices. It is sometimes used to indicate a circuit having its battery arranged in series. It should be restricted to the first definition.

123 STANDARD ELECTRICAL DICTIONARY.

Circuit, Derived.

A partial circuit connected to two points of another circuit, so as to be in parallel with the portion thereof between such two points; a shunt circuit.

Synonyms--Shunt Circuit--Derivative Circuit--Parallel Circuit.

Circuit, Electric, Active.

A circuit through which a current pa.s.ses. The circuit itself need only be a conducting ring, or endless wire. Generally it includes, as part of the circuit, a generator of electro-motive force, and through which generator by conduction, ordinary or electrolytic, the same current goes that pa.s.ses through the rest of the circuit. One and the same current pa.s.ses through all parts of a series circuit when such current is constant.

A current being produced by electro-motive force, and electromotive force disappearing in its production in an active circuit, there must be some source of energy which will maintain electromotive force against the drain made upon it by the current.

The simplest conception of an active electric circuit is a ring or endless conductor swept through a field of force so as to cut lines of force. A simple ring dropped over a magnet pole represents the simplification of this process. In such a ring a current, exceedingly slight, of course, will be produced. In this case there is no generator in the circuit. An earth coil (see Coil, Earth,) represents such a circuit, with the addition, when experimented with, of a galvanometer in the circuit.

In practice, a circuit includes a generator such as a battery or dynamo, and by conductors is led through a continuous path. Electric lamps, electrolytic cells, motors and the like may be included in it.

The term "circuit" is also applied to portions of a true circuit, as the internal circuit, or external circuit. A certain amount of elasticity is allowed in its use. It by no means necessarily indicates a complete through circuit.

Circuit, Electrostatic.

(a) A circuit through which an electrostatic or high tension discharge takes place. It is virtually an electric circuit.

(b) The term is applied also to the closed paths of electrostatic lines of force.

Circuit, External.

The portion of a circuit not included within the generator.

Circuit, Grounded.

A circuit, one of whose members, the return circuit, is represented by the earth, so that the earth completes the circuit. In telegraphy each end of the line is grounded or connected to an earth-plate, q. v., or to the water or gas-pipes, and the current is a.s.sumed to go through the earth on its return. It really amounts to a discharging at one end, and charging at the other end of the line. The resistance of the earth is zero, but the resistance of the grounding or connection with the earth may be considerable.

Synonyms--Ground Circuit--Earth Circuit--Single Wire Circuit.

[Transcriber's note: The resistance of the earth is high enough that large power system return currents may produce dangerous voltage gradients when a power line is shorted to the ground. Don't walk near downed lines!]

124 STANDARD ELECTRICAL DICTIONARY.

Circuit Indicator.

A pocket compa.s.s, decomposition apparatus, galvanometer or other device for indicating the condition of a wire, whether carrying a current or not, and, if carrying one, its direction, and sometimes roughly indicating its strength.

Circuit, Internal.

The portion of an electric circuit included within the generator.

Circuit, Line.

The portion of a circuit embracing the main line or conductor, as in a telegraph circuit the line carried on the poles; distinguished from the local circuit (see Circuit, Local,) in telegraphy.

Circuit, Local.

In telegraphy, a short circuit with local generator or battery included, contained within the limits of the office or station and operated by a relay, q. v. This was the original local circuit; the term is applicable to any similar arrangement in other systems. Referring to the cut, the main line circuit includes the main battery, E, Key, P, Relay, R, ground plates, G, G1. The relay magnet opens and closes the local circuit with its local battery, L, and sounder magnet, H, with its armature, B. The minor parts, such as switches, are omitted.

Fig. 90. LOCAL CIRCUIT OF TELEGRAPH SYSTEM.

Circuit, Local Battery.

A local circuit worked by and including a local battery in its course.

125 STANDARD ELECTRICAL DICTIONARY.