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
A short circuit is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit.
The opposite of a short circuit is an open circuit, which is an infinite resistance between two nodes.
Tree limbs cause a short circuit, triggering an electrical arc during a storm.