Circuit Breaker is a mechanical device designed to close or open contact members, thus closing or opening an electrical circuit under the normal or abnormal conditions.
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.
Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance to large switchgear designed to protect high voltage circuits feeding an entire city.