What might be a sign that a motor experiences high slip?

When a motor experiences high slip, it indicates that the difference between the synchronous speed and the actual speed of the motor is significant. This often occurs when the motor is under heavy load and struggles to maintain its rated speed. As the load increases, the rotor's speed decreases relative to the magnetic field's speed, which decreases efficiency and affects the motor's performance.

In this context, if a motor has difficulty maintaining speed under load, it signifies that it cannot keep up with the synchronized rotation of the magnetic field, leading to a higher slip condition. This is a key indicator that the motor is experiencing issues.

The other choices do not accurately reflect the characteristics associated with high slip conditions. A motor that runs quietly is typically functioning well, while running at synchronous speed suggests efficient operation rather than a problem. Excess heat can be a symptom of motor issues, but it is not as direct an indicator of high slip compared to speed maintenance challenges.