What happens to the wire in a fuse if the current exceeds a certain limit?

When the current flowing through a fuse exceeds its rated limit, the wire within the fuse melts. This is due to the principle of overheating. Fuses are designed to protect electrical circuits by interrupting the flow of current when it becomes too high. The wire inside the fuse is made of a material that has a relatively low melting point.

When the current increases beyond the fuse's capacity, the electrical resistance in the wire generates heat as a byproduct of the electrical flow. If this current continues unchecked, the heat produced will eventually reach the point where the wire cannot withstand it any longer, causing the wire to melt and break the circuit. This interruption in the circuit prevents further electrical flow, thus protecting equipment and preventing potential hazards such as electrical fires.

The other options such as shorting out, glowing, or expanding may represent electrical behaviors under different conditions, but the fundamental safety mechanism of a fuse is specifically designed to melt upon excessive current flow to ensure the circuit is safely interrupted.