Which device is commonly used to interrupt current flow in an emergency?

A fuse is specifically designed to provide overcurrent protection in electrical circuits and is commonly used to interrupt current flow in case of an emergency. It contains a metal wire or strip that melts when the current exceeds a certain level, breaking the circuit and stopping the flow of electricity. This mechanism prevents overheating and potential fire hazards caused by excess current.

In contrast, while a switch can also interrupt current flow, it is typically used for normal operation and does not automatically respond to emergency conditions. Relays can interrupt current as part of a control system, but they are not primarily designed for emergency situations. A transformer, on the other hand, is used for voltage conversion and does not interrupt current flow at all. Thus, the fuse stands out as the correct choice for emergency current interruption.