Circuit

Circuit, Electric. When two points are connected by an electrical conductor, between which points a definite difference of potential may be kept up, a circuit is said to be formed, and a current will be set up whose strength is proportional to the magnitude of the electromotive-force supplied, and to the conductivity of the complete circuit. If the circuit be broken, i.e. if the continuity of the conductor from the one given point to the other be disturbed by the introduction of a very high resistance, then the transfer of electricity is practically stopped. The quantity of electricity displaced per second across any section is the same for all parts of the circuit, and is a measure of the strength of the current. The energy spent per second during the flow of the current through any part of this circuit may be understood to be the energy lost by the above quantity lowering its potential. If A is the current in amperes, and V the potential-difference in volts at the two ends of the specified portion of the circuit, AV measures the energy given per second to that portion, and AV / 746 gives us at once the horse-power employed. This is a very useful expression in practical work.