Which device blows or melts to break a circuit when overheated due to overload?

• A. A fuse
• B. Circuit breaker
• C. Ground fault interrupter
• D. Surge protector

Answer: (A)

A fuse is the protective device that is designed to blow open by melting when too much current flows. Its thin metal link carries normal current, but when overload pushes the current beyond its rating, the resulting heat melts the link and the circuit is interrupted. Because it sacrifices itself, a fuse must be replaced after it blows.

A circuit breaker also protects against overload, but it works by opening a switch through a thermal or magnetic mechanism rather than melting. It’s resettable after the fault is cleared. Ground fault interrupters detect imbalances between hot and neutral and trip to prevent shock, not specifically to stop overheating from overload. Surge protectors handle voltage spikes, clamping excess voltage rather than designed to blow the circuit through melting.