Which of the following is an electrical safety device that interrupts current flow?

The circuit breaker is an essential electrical safety device designed specifically to interrupt the current flow in a circuit when an overload or short circuit occurs. It effectively protects electrical systems from damage by automatically breaking the circuit, thereby preventing excessive current from flowing. This functionality is crucial for safeguarding appliances, wiring, and the overall electrical infrastructure from the dangers of overheating or electrical fires that can result from faulty wiring or overloaded circuits.

In contrast, while a switch can open or close a circuit, it does not have the protective mechanism to sense an overload and interrupt the current flow accordingly. A transformer is used to change the voltage levels in AC circuits but does not provide any direct interruption of current flow. A relay is an electromechanical switch that can control the operation of electrical circuits but, like a switch, it does not inherently interrupt current for safety purposes like a circuit breaker. Thus, the circuit breaker is uniquely designed for safety, which makes it the correct answer in this context.