What distinguishes a fuse from a circuit breaker?

The correct answer highlights a key functional difference between a fuse and a circuit breaker when it comes to their operation during an overcurrent situation. A fuse operates by melting its internal wire or element when the current exceeds a predetermined limit, thus interrupting the electrical flow and protecting the circuit from damage due to excessive current. This process is irreversible, meaning once a fuse has blown, it must be replaced with a new one to restore the circuit.

On the other hand, a circuit breaker is designed to automatically interrupt current flow when it detects an overcurrent condition, but it does not physically destroy an internal component like a fuse does. Instead, circuit breakers can be reset after they trip, allowing for quicker and easier restoration of service without needing to replace a component. This characteristic makes circuit breakers more convenient and reusable compared to fuses.

Thus, the essence of the distinction is that a fuse operates through a one-time physical alteration, whereas a circuit breaker can be reset for repeated use, providing ongoing protection without the need for replacement after an overcurrent event.