Which device is specifically designed to prevent electrical overload?

The device specifically designed to prevent electrical overload is a fuse. A fuse operates as a safety mechanism in electrical circuits. It is essentially a thin strip of metal that melts when the current flowing through it exceeds a predetermined level. This melting action breaks the circuit and stops the flow of electricity, thereby preventing potential damage to the electrical components, wiring, and reducing the risk of fire caused by overheating.

In the context of the other options, a transformer is used to change the voltage of alternating current, a capacitor stores electrical energy and is used for filtering and timing applications, while a resistor is used to limit the flow of electric current in a circuit. These devices serve distinct purposes related to managing electric signals and energy, but they do not have the primary function of preventing electrical overload like a fuse does.