An over-current protective device, which consists of a conductor, that melts and opens the circuit when the current exceeds a certain ampere value for a certain duration. Fuses can be designed to have a long or short trip time depending on how critical small overloads are to a circuit. The trip time on a direct short circuit is almost instantaneous. Current limiting fuses are designed to trip very rapidly and to limit the energy in a short circuit to a small value, thus preventing a possible electrical explosion. (see: Circuit Breaker.)