A fuse contains a thin strip or wire of metal designed to melt and vaporize at a specific current threshold. When a short circuit or severe overload occurs, the element breaks, stopping the flow of electricity and preventing a fire. Because they are destroyed in the process, they must be physically replaced after clearing the fault. They are still heavily used in industrial disconnects and multimeters for their extremely fast reaction times.
Heard on the job
The motor locked up and blew the 30-amp fuse in the disconnect switch.
Insider tip
Never replace a blown fuse with one of a higher amperage rating, or bypass it with copper tubing, a practice that causes catastrophic fires.
Do not mix it up with
- Circuit breaker: A breaker is a mechanical switch that resets, whereas a fuse physically burns out and requires replacement.