What happens to the circuit when a fuse blows?

When a fuse blows, it acts as a safety mechanism that interrupts the flow of electricity in a circuit. This interruption occurs because the fuse contains a thin metal wire that melts when excessive current flows through it, effectively severing the connection. As a result, the circuit becomes open, meaning there is a discontinuity in the path through which current can flow. This open circuit prevents any electrical energy from reaching the devices connected to it, thereby protecting them from potential damage caused by overcurrent situations.

In contrast, the other options do not accurately describe the behavior of the circuit when a fuse blows. A closed circuit allows electricity to flow, a shorted circuit typically refers to an unintended low-resistance connection that can cause excessive current and potential safety hazards, and powering on the circuit would imply the devices connected are operational, which is not the case when a fuse has blown.