A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by current in excess of that which the equipment can safely carry (overcurrent). Its basic function is to interrupt current flow to protect equipment and to prevent fire. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset to resume normal operation.
A two-pole miniature circuit breaker
An air circuit breaker for low-voltage (less than 1,000 volt) power distribution switchgear
Four one-pole miniature circuit breakers
Front panel of a 1250 A air circuit breaker manufactured by ABB. This low-voltage power circuit breaker can be withdrawn from its housing for servicing. Trip characteristics are configurable via DIP switches on the front panel.
In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. It is a sacrificial device; once a fuse has operated, it is an open circuit, and must be replaced or rewired, depending on its type.
A miniature time-delay 250 V fuse that will interrupt a 0.3 A current at after 100 s, or a 15 A current in 0.1 s. 32 mm (1 1/4") long.
HRC fuse with red blown indication
Various holders for cartridge ferrule fuses
A set of pole-top fusible cutouts with one fuse blown, protecting a transformer - the white tube on the left is hanging down