What device interrupts the flow of electrical current when overloaded?

The device that interrupts the flow of electrical current when overloaded is a fuse. A fuse is specifically designed to enhance electrical safety by protecting circuits from excessive current that could lead to overheating or fires. When the current flowing through a fuse exceeds its rated capacity, the metal wire inside it melts due to the heat generated by the excessive current. This melting breaks the circuit, thus stopping the flow of electricity and preventing potential damage to electrical devices or systems.

In contrast, while a relay can control the flow of electricity based on certain conditions, it does not function as a safety device for overload protection. A transformer is primarily used to change voltage levels in an electrical system and does not interrupt current flow. A resistor is used to limit or manage current flow and does not provide overload protection either; it simply dissipates electrical energy as heat.