What components provide over-current protection?

• A. Relays and transformers
• B. Inductors and resistors
• C. Fuses and circuit breakers
• D. Capacitors and diodes

Answer: (C)

Over-current protection is about interrupting the current when it becomes excessive to prevent damage or fire. Fuses and circuit breakers are designed for this role. A fuse contains a thin metal link that melts and opens the circuit when the current exceeds its rating, providing a one-time protection that must be replaced after it blows. A circuit breaker uses a thermal or magnetic mechanism to trip and open the circuit when the current is too high, and it can be reset after the fault is cleared. Together, they stop dangerous surges and short circuits from heating wires or components.

Other components don’t provide automatic over-current protection. Relays and transformers are mainly for switching and voltage transformation, not for automatically interrupting fault currents. Inductors and resistors influence current flow but don’t reliably limit or disconnect it under fault conditions. Capacitors and diodes handle energy storage and rectification, not protection against sustained excessive current.