How does a thermal switch protect an electric motor?

A thermal switch protects an electric motor by opening the circuit at a predetermined temperature. This device functions as a safety mechanism designed to monitor the temperature of the motor. When the temperature reaches a specified threshold that indicates potential overheating, the thermal switch responds by breaking the electrical circuit, effectively shutting off power to the motor. This action prevents further temperature rise that could lead to damage or failure of the motor, thus ensuring operational safety and longevity.

The other options do not provide an effective protective mechanism for motors. Increasing the motor speed can lead to excessive heat generation, while reducing the power supply doesn't directly address the overheating issue. Regulating the voltage may improve performance but won't specifically safeguard against thermal overload conditions. Hence, the thermal switch's role in cutting off electrical supply when a specific temperature is surpassed is crucial for motor protection.