How do many circuit breakers function?

Circuit breakers are designed to protect electrical circuits from overloads and short circuits, and they primarily operate based on two fundamental principles: thermal and magnetic actions.

Thermally, circuit breakers utilize a bimetallic strip that bends when heated due to current overload. This bending action eventually triggers the circuit breaker to open, interrupting the electrical flow and preventing potential damage.

Magnetically, circuit breakers employ an electromagnet that activates when the current exceeds the predetermined threshold. The magnetic force generates a strong pull that trips the breaker, quickly disconnecting the power supply to avoid hazards, such as fires or equipment failure.

Given these workings, thermal and magnetic responses are central to how most circuit breakers function, making this the correct answer. In contrast, other options such as electrical or digital mechanisms (which refer to entirely different systems), hydraulic or pneumatic methods (related to fluid dynamics), and manual or automatic controls (which describe modes of operation rather than function) do not accurately capture the primary functioning modes of circuit breakers.