Which protective device is designed to interrupt current when a fault occurs and is typically replaceable after a fault?

• A. Circuit breaker
• B. Fuse
• C. Resistor
• D. Diode

Answer: (B)

A fuse is the protective device that interrupts current when a fault occurs and is typically replaceable after a fault. It contains a thin metal link that melts when the current exceeds its rating due to a fault or surge, opening the circuit to prevent damage. Because the link is sacrificial, once it blows you replace the fuse with a new one; it isn’t resettable. A circuit breaker also interrupts fault current but is designed to trip and be reset, not usually replaced after a fault. A resistor simply limits current and dissipates heat, not interrupting faults. A diode controls the direction of current and doesn’t provide overcurrent protection.