The basic principle of a fuse

The core component of a fuse is its internal metal wire or alloy. When current flows through it, the wire heats up due to the thermal effect of the current. If the current exceeds the fuse's rated value, the wire melts and breaks the circuit. This is a single-use protection device; once it blows, the fuse needs to be replaced.

In the design of fuses, the internal metal wire is typically made of pure metal or alloy, with the chosen material having a low melting point and a certain resistance. The resistivity and melting point of the fuse's internal metal wire are precisely selected based on its operating environment. For example, common materials such as lead, tin, and silver can be rapidly heated to their melting point and melt when the current is overloaded.