How does a fuse protect electrical circuits?

A fuse serves the crucial role of protecting electrical circuits by melting and breaking the circuit during an overcurrent situation. When the current flowing through the fuse exceeds its rated capacity, the increased heat generated causes the fuse's metal conductor to melt. This action interrupts the flow of electricity, effectively preventing potential damage to electrical components and avoiding risks such as overheating or fire.

This mechanism of action is fundamental to circuit protection, as it ensures that excessive current does not continue to flow around the circuit, which could lead to damage or hazardous conditions. It is a passive safety feature that works without the need for any external intervention or mechanical operation.

The other options describe mechanisms that do not accurately fit the purpose or operation of a fuse. For instance, reducing voltage output or increasing resistance does not provide the direct protection against overcurrent that a fuse specializes in. Similarly, redirecting current to ground is more characteristic of grounding or surge protection techniques rather than the functioning of a fuse.