What component is found in thermal circuit breakers?

A thermal circuit breaker is designed to protect electrical circuits from overheating by utilizing a specific component known as a bimetal strip. The bimetal strip is made from two different metals that expand at different rates when heated. This characteristic allows the strip to bend as the temperature rises due to excessive current flow. When the bimetal strip bends sufficiently, it opens the circuit, thereby interrupting the flow of electricity and preventing damage to the circuit components.

The other options represent components that are typically used in different types of protective devices. A spring-loaded electrical contact might be associated with devices that require mechanical operation to open or close a circuit based on pressure or physical adjustment, not thermal changes. An electromagnetic coil is found in devices like electromagnetic circuit breakers, which react to overcurrent by generating a magnetic field that pulls a mechanism to cut off the circuit. A fuse element is utilized in traditional fuses where it melts under excessive current to break the circuit but does not have the reset capability that a thermal circuit breaker does with its bimetallic mechanism.

Thus, the unique feature of the bimetal strip in thermal circuit breakers is why it is the correct choice.