The wire that melts and breaks a circuit if too much current is flowing is called a fuse.

Here's how it works:

* Fuses contain a thin wire made of a metal with a low melting point.

* When too much current flows through the fuse, the wire heats up due to the resistance.

* If the current exceeds the fuse's rated capacity, the wire melts, creating a break in the circuit and stopping the flow of electricity.

This prevents damage to other components or even fire hazards caused by excessive current.

There are also circuit breakers, which serve a similar purpose but use a different mechanism. Circuit breakers use an electromagnet that trips a switch to open the circuit when current exceeds a certain level. However, they can be reset after the overload condition is removed, unlike fuses, which need to be replaced after melting.