What defines a circuit breaker in electrical systems?

A circuit breaker is defined as a device designed to protect an electrical circuit from damage caused by over-current or short circuits. When the current flowing through the circuit exceeds a predetermined level, the circuit breaker automatically interrupts the flow of electricity, thereby preventing overheating and potential fires. This automatic function is crucial for ensuring safety in electrical systems.

The inclusion of the option for manual operation highlights its versatility; the handle can be pushed to open the circuit intentionally, allowing for maintenance or troubleshooting without the risk of electric shock. Thus, the description perfectly encapsulates the dual ability of circuit breakers to respond to both automatic triggers from over-current situations and manual interventions.

In contrast, other options do not accurately describe a circuit breaker. Voltage regulation pertains to devices like voltage regulators or transformers, which manage voltage levels rather than interrupt current flow. A fuse does act as a safety device in electrical circuits by melting and breaking the circuit when over-current occurs, but it does not reset like a circuit breaker; it must be replaced after it blows. The final option suggests that a circuit breaker is active only in overload situations, which does not encompass its full functionality, as it also includes manual operation and other protective features.