What safety device contains a metal strip that melts to stop current flow?

The safety device that contains a metal strip that melts to stop current flow is a fuse. A fuse is designed to protect electrical circuits from excessive current that can cause overheating and potentially lead to electrical fires or damage to equipment.

When the current flowing through the fuse exceeds its rated capacity, the metal strip inside the fuse heats up due to electrical resistance. Eventually, this strip melts, breaking the circuit and stopping the flow of current. This action prevents further electricity from flowing through the circuit and protects both the wiring and connected devices.

While circuit breakers and relays are also safety devices, they operate on different principles. A circuit breaker can be reset after it trips, while a relay is used for switching circuits but does not inherently provide overload protection like a fuse does. A transformer, on the other hand, is used to change voltage levels and does not serve a protective function. Thus, the fuse is the correct choice for a device that uses a metal strip to cut off current flow in the event of overcurrent situations.