What is the main function of a thermal circuit breaker?

The main function of a thermal circuit breaker is to trip and open a circuit when excessive current flows. This is crucial for protecting electrical circuits from damage caused by overloads or short circuits. When the current exceeds a predetermined threshold, the thermal mechanism heats up and eventually causes the breaker to open the circuit, thereby interrupting the flow of electricity. This self-resetting mechanism ensures that, once the circuit cools down, the breaker can close again automatically, reducing the risk of equipment damage and electrical fires.

The other options do not align with the operational principles of thermal circuit breakers. For instance, providing a permanent connection in a circuit is a characteristic of switches or connections, not circuit breakers. Amplifying current is a function of devices designed for signal processing, not protective devices like circuit breakers. Similarly, measuring voltage is the role of voltmeters, not thermal circuit breakers, which focus solely on protecting circuits from excessive current, emphasizing their critical role in electrical safety and system integrity.