Which type of overload relay utilizes a resistive heating element to operate?

The correct response identifies the thermal overload relay as the type that employs a resistive heating element for its operation. In thermal overload relays, current passing through a resistive element generates heat. This heat causes the element, often a bimetallic strip, to bend due to the differential expansion rates of the materials. As the strip bends, it activates a mechanism that opens the circuit, effectively providing protection to the motor by cutting off power in the case of an overload condition.

This design is fundamental to the operation of thermal overload relays, as they respond to the heat generated by excessive current rather than directly sensing magnetic fields or using electronic components, which characterizes other types of overload protective devices. By prioritizing the temperature increase due to prolonged overcurrent situations, thermal overload relays protect motors from damage caused by overheating.