A fuse is a type of over-current protection device. The essential component in a fuse is a metal wire or strip that melts when too much current flows through and that interrupts the circuit in which it is connected. Short circuit, overload or device failure is often the reason for excessive current.
A fuse interrupts excessive current so that further damage by overheating or fire is prevented. Over-current protection devices are essential in electrical systems to limit threats to peoples’ lives and property damage. Fuses can sometimes be used instead of circuit breakers. They have the advantages of often being less costly and simpler than a circuit breaker for similar uses. A blown fuse must be replaced with a new device which is less convenient than simply resetting a breaker and therefore likely to discourage people from ignoring the faults. On the other hand, replacing a fuse without isolating the circuit first (most building wiring designs do not provide individual isolation switches for each fuse) can be dangerous in itself, particularly if the fault is a short circuit.