Final answer:
Thermal cut outs in circuits respond more quickly when the overload current increases, due to the rise in temperature caused by the excessive current flow. Fuses and circuit breakers are also used for current protection, with circuit breakers providing a faster response.
Step-by-step explanation:
The operation of a thermal cut out or thermal protection device in a circuit is to prevent overheating and potential damage by opening the circuit when excess current is detected. When an overload current is present, the amount of current flowing through the thermal cut out's element increases, resulting in its temperature rising. As the overload current increases, the temperature of the thermal cut out rises more quickly, which in turn causes it to open the circuit more rapidly to prevent damage. This is because the thermal cut out operates on the principle of heat: when the device gets too hot (due to high current), it triggers a mechanism to open the circuit and halt the current flow.
Most fuses and circuit breakers are designed to handle high currents for a short period, especially during the startup of devices like electric motors where current spikes can be significant. Fuses offer a one-time protection and need to be replaced after they are blown while circuit breakers can be reset. The circuit breakers respond much faster to overload conditions compared to thermal cutouts which are designed to react to sustained overcurrents.