A fuse is a protection component designed to break a circuit when too much current flows. It contains a metal element that melts when current exceeds a safe level for long enough.
Why fuses are used
Fuses help protect wires, components, devices, and sometimes people from overheating and fire risk caused by excessive current. They are common in appliances, cars, power supplies, battery packs, and electronic equipment.
Fuse versus resettable protection
A normal fuse must be replaced after it blows. Some circuits use resettable fuses, circuit breakers, or electronic protection instead. The right choice depends on the circuit and safety requirements.
A fuse is simple, but it plays an important role: it fails on purpose so the rest of the circuit has a better chance to survive.