Which protective device is described as interrupting current when an overcurrent is detected, commonly realized by melting a fusible link?

• A. Fuses
• B. Circuit breakers
• C. Ground fault interrupters
• D. Arc fault interrupters

Answer: (A)

Overcurrent protection that works by a sacrificial element melting to open the circuit is describing a fuse. A fuse contains a thin metal link that heats up when current exceeds its rating; when it reaches its melting point, the link melts and interrupts the circuit. This single-use device is designed to fail safe by removing the current path, and then it must be replaced after it blows.

Circuit breakers, in contrast, interrupt by tripping a switch (thermal or magnetic) and can be reset after clearing the fault. Ground fault interrupters detect imbalances between hot and neutral currents and trip on leakage, not simply overcurrent. Arc fault interrupters monitor arcing patterns to trip, also not based on melting a fusible link.