Which device is used to protect circuits from overloads by breaking the circuit connection?

The device used to protect circuits from overloads by breaking the circuit connection is a circuit breaker. Circuit breakers are essential safety devices that automatically interrupt the flow of electricity when they detect an overload or a short circuit. This interruption prevents damage to the electrical system and reduces the risk of fire or other hazards associated with overcurrent situations.

Circuit breakers work by sensing the amount of current flowing through the circuit. When the current exceeds a predetermined level, the circuit breaker will "trip," effectively opening the circuit and stopping the flow of electricity. This mechanism allows for easy resetting once the issue is resolved, making circuit breakers a reusable protective solution.

In contrast, transformers are used to change the voltage levels in an electrical system and do not provide protection against overloads. Fuses also serve a similar protective function but differ in that they need to be replaced after they blow; they do not allow for resetting like circuit breakers. Relays are electromagnetic switches used to control the operation of high-power circuits but do not inherently provide overload protection. Therefore, the circuit breaker stands out as the device specifically designed for protecting circuits by breaking the connection during overload conditions.