Which component protects circuits from overload?

• A. Fuse
• B. Resistor
• C. Capacitor
• D. Transformer

Answer: (A)

Overcurrent protection is needed to prevent insulation damage and fire when current exceeds what wiring and components can safely handle. A fuse is designed for this purpose. It contains a metal conductor that carries normal current; when the current goes beyond its rating, the conductor heats up and melts, breaking the circuit. This fast interruption stops the flow before overheating can cause harm, and it’s why fuses are common protection devices. They are simple, reliable, and designed to trip on overload. However, the device is single-use; after a trip you replace the fuse and inspect the circuit.

The other components have different roles: a resistor limits current in a circuit but does not physically disconnect the circuit during an overload; it will simply dissipate more heat and can fail, potentially causing more problems. A capacitor stores energy and helps smooth voltage or provide bursts, but it does not interrupt current when overload occurs. A transformer shifts voltage and current levels, but it does not automatically cut off current in an overload situation. So the fuse is the protective element that actively guards the circuit against overload.