A circuit breaker is a device designed to shut off an electrical circuit when too much current is flowing. This usually occurs if too many devices are plugged in or if there is a short circuit. Circuit breakers are usually installed in the electrical panel. Some circuit breakers also have GFCI protection. Inside the circuit breaker, there is usually an electromagnetic coil. When too much current flows through the coil, it pulls on the switch, shutting the power off. The coil reacts to immediate short circuits. There is also a bimetal strip that will bend and pull on the switch if it gets too hot. This reacts to extended periods of too much current. 