Physics

Why do fuses have different power ratings?

fuse

Normally the diameter and resistance of the wire.

Fuses work by getting hot when an electrical current flows through them – hot enough to melt and then break. But they need to operate indefinitely at the correct current. The wire can also be engineered so that it breaks very quickly when a current is exceeded – by holding it in tension with a spring. As the fuse weakens on heating, the spring makes sure it snaps.