What function do thermal switches serve in their normal condition?

Thermal switches function primarily as safety devices within electrical systems, and in their normal condition, they are open, meaning they do not allow current to flow. This state is crucial for preventing overheating and potential damage in the system. When the temperature rises to a predetermined level, the thermal switch responds to the heat, closing the circuit and allowing current to pass. This action enables the system to activate safety measures or cooling devices, thus preventing failures due to excessive temperatures.

In contrast, if thermal switches were closed and continuously allowed current to pass, that would lead to a risk of overheating without any protective mechanisms being engaged. They are not active at all times because their purpose is to respond to temperature changes rather than maintain a constant operational state. Furthermore, thermal switches do not provide constant feedback; they only transition states based on temperature changes and act accordingly.