circuit breaker

circuit breaker cir"cuit break"er, n. (Elec.) A device contained within an electrical circuit designed to interrupt the circuit when the current exceeds a preset value; it is sometimes called a {contact breaker}. Its function is to prevent fire or damage to the circuit or the devices on the circuit which could be caused by excess current, such as that caused by a short-circuit. It differs from a {fuse} in not having a conducting element which melts (see 2nd {fuse}, n.). Circuit breakers are designed to be easily reset, i. e. to reclose the circuit after it has been opened by the circuit breaker; this is usually accomplished by simply moving a switch back and forth. They are commonly used in buildings to protect individual electrical lines, and are often contained in groups within a box called a circuit breaker panel, which divides the current from a main electrical line into multiple circuits each protected by a separate circuit breaker. Less commonly they may be found on individual devices. [PJC]