Which of the following best describes a safety device that melts under excessive current?

A safety device that melts under excessive current is known as a fuse. A fuse is specifically designed to protect electrical circuits by melting and interrupting the flow of electricity when the current exceeds a predetermined level. This action prevents overheating and potential damage to the wiring and connected devices, safeguarding both the equipment and the premises.

Fuses work by having a conductive wire that melts when the current gets too high, effectively breaking the circuit. Once a fuse is blown, it must be replaced to restore functionality, as the melted wire is permanently damaged.

In contrast, devices like circuit breakers can be reset after they trip due to excess current and do not melt; they function by mechanically switching off the power. Transformers and diodes serve different purposes in electrical systems – transformers change voltage levels, and diodes control the direction of current flow but do not act as safety devices in the same manner as a fuse.