What is the purpose of a protective device in a circuit and name two common types?

• A. To interrupt fault current and protect personnel and equipment.
• B. To store energy for use during peak load; capacitors and batteries.
• C. To regulate voltage; transformers and regulators.
• D. To measure current; ammeters and clamps.

Answer: (A)

Protective devices are meant to interrupt current when something goes wrong in a circuit, so faults don’t cause damage to equipment or harm to people. By quickly opening the circuit during an overcurrent or fault condition, they isolate the faulty part and stop the flow of electricity, reducing the risk of overheating, insulation damage, and fire.

Two common types are fuses and circuit breakers. A fuse has a thin metal link that heats up and melts when current is too high, permanently breaking the circuit. A circuit breaker senses excess current and trips a mechanical switch to open the circuit, and it can be reset after the fault is cleared. This rapid interruption is essential for safety and system protection.

Other devices described in the choices, like energy storage elements or voltage regulators, don’t serve the protective interrupting role, and instruments used to measure current aren’t designed to automatically disconnect the circuit.