Fuse

In electronics and electrical engineering a fuse (from the Latin "fusus" meaning to melt) is a type of sacrificial overcurrent protection device. Its essential component is a metal wire or strip that melts when too much current flows, which 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 (blows) so that further damage by overheating or fire is prevented. Wiring regulations often define a maximum fuse current rating for particular circuits. Overcurrent protection devices are essential in electrical systems to limit threats to human life and property damage. Fuses are selected to allow passage of normal current and of excessive current only for short periods.

There are two types of fuses which can be described as single use or resettable fuses. Single use fuses commonly contain a small strip of wire which when heated breaks and stops current flow. Resettable fuses contain a conductive thermoplastic which when heated delivers a high impedance essentially creating an open circuit. As the current lowers heat begins to dissipate from the fuse returning it to its original low impedance state.

A fuse was patented by Thomas Edison in 1890 as part of his successful electric distribution system.