What effect does increasing the frequency of the power supply have on a single-phase motor?

Increasing the frequency of the power supply has a direct impact on the synchronous speed of a single-phase motor. The synchronous speed, which is the speed at which the motor's magnetic field rotates, is calculated using the formula:

[ \text{Synchronous Speed (RPM)} = \frac{120 \times \text{Frequency (Hz)}}{\text{Number of Poles}} ]

As the frequency increases, the synchronous speed also increases, assuming the number of poles remains constant. This relationship means that with a higher frequency applied to the motor, it is capable of achieving a higher speed of operation. This characteristic is crucial in applications where faster motor performance is needed, allowing the motor to adapt to changing requirements.

In contrast, the other choices do not accurately represent the effects of increasing the power supply frequency. For example, while increasing frequency might affect torque under certain conditions, the primary and direct effect relates to synchronous speed, making the second choice the clearly appropriate answer in the context of how frequency affects motor function.