Which mechanical switching device is responsible for making, carrying, and breaking current under normal and abnormal circuit conditions?

A circuit breaker is a mechanical switching device specifically designed to interrupt the flow of electricity in a circuit under both normal and abnormal conditions. Its primary function is to protect electrical circuits by automatically switching off the current flow when significant overloads or faults occur, such as short circuits.

In normal operations, the circuit breaker carries current; when it detects any anomalies that could lead to overheating, electrical fires, or damage to connected equipment, it can promptly break the circuit. This capacity to make, carry, and break the current is crucial for safety in power distribution systems.

Other devices listed, like transformers and relays, serve different purposes. A transformer is used to change voltage levels and does not interrupt current on its own, while a relay is more about signaling and does not directly handle or switch large currents like a circuit breaker does. The general term “switching device” can encompass several types of equipment, but does not specifically denote the function of making and breaking current under varying circuit conditions as accurately as a circuit breaker does.