What function does a Residual Current Device (RCD) serve?

A Residual Current Device (RCD) is designed to enhance electrical safety by monitoring the flow of electrical current in a circuit. Specifically, it detects any imbalance between the live (phase) and neutral wires. When an imbalance is detected, which indicates that some of the current is leaking to earth (often through a faulty appliance or wiring), the RCD quickly disconnects the electrical supply. This mechanism significantly reduces the risk of electric shock and electrical fires that can occur due to faults in the wiring or appliances.

The other options do not accurately capture the purpose of an RCD. For instance, regulating voltage is associated with devices such as voltage stabilizers or transformers, while preventing overheating pertains to circuit breakers and fuses. Providing additional power during high loads is typically a function of generators or power conditioners, not an RCD. Thus, option B accurately reflects the RCD's critical role in protecting users by cutting off electricity when a current imbalance is detected.