Which device acts as a safety switch to interrupt current if it detects an overload, protecting the circuit?

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

Answer: (D)

A circuit breaker is designed to protect a circuit by automatically interrupting current when the load draws too much or a fault creates a short. It uses a sensing element—thermal, magnetic, or a combination of both—to detect overcurrent and trigger a switch that opens the circuit, stopping the flow of electricity. This makes it a reusable safety switch: after the fault is resolved, you can reset it to restore power.

This differs from a fuse, which is a one-time protective element that melts open when overheated and must be replaced. It also isn’t like a transformer, which simply changes voltage levels rather than providing a interruption. And it isn’t like a resistor, which only limits current under normal operation and does not automatically disconnect power during a fault.