Question

What is a fuse? How does it work?

Answer 1

Fuse a thin piece of wire designed to carry a limited electrical current. If you try to pass a higher current through the wire, it'll heat up so much that it burns or melts. When it melts, it breaks the circuit it's fitted to and stops the current from flowing.

The function of a fuse is usually to prevent fire - that's the basic protection fuse offers - between power supply and appliance there may be a few feet or metres of cable - if a short circuit occurs in the appliance, the cable could easily become overheated (due to excess current) and burn or rupture its insulation.