Circuit Breaker Function Explained

The question asks to identify a device used as a circuit breaker. A circuit breaker's primary function is to interrupt the flow of electrical current in a circuit when it becomes unsafe, typically due to an overload or short circuit.

Role of a Fuse

A fuse is specifically designed for this purpose. It contains a wire or filament that melts and breaks the circuit when the current exceeds a predetermined safe level. This protects the circuit and connected appliances from damage.

• Fuse: Acts as a sacrificial device to break the circuit automatically upon overcurrent.

Why Other Options Are Less Suitable

Let's look at the other options:

• Resistor: Resistors are used to impede or resist the flow of current but do not break the circuit.
• Switch: A switch is used for manual control; it opens or closes a circuit by user action but does not automatically protect against overcurrents.
• Resettable protective device: This is a broader category that includes modern circuit breakers (like MCBs). While fuses also protect circuits, the specific option 'fuse' directly represents a classic type of device used for this function and is often the intended answer in basic contexts. Given the options and the common understanding, the fuse is the most direct answer representing a device used *as* a circuit breaker.

Therefore, a fuse is commonly used as a simple and effective circuit breaker.