What is the primary function of a circuit breaker?

The primary function of a circuit breaker is to protect electrical equipment from current surges and overloads. Circuit breakers are designed to monitor the flow of electrical current in a circuit. When they detect an increase in current beyond a safe limit—due to an overload or a short circuit—they automatically interrupt the circuit by opening it. This action helps prevent potential damage to both the electrical equipment and the wiring by mitigating the risk of overheating, fires, or equipment failure.

In contrast, while protecting against incoming spike voltage is important for different devices (such as surge protectors), it is not the main role of a circuit breaker. Similarly, breaking power flow due to very low voltage or tripping when encountering very low current are not standard functions associated with circuit breakers, which are primarily concerned with the safe operation during conditions of excess current. This focus on current surges and overloads forms the basis of why B is the correct answer.