What does slip refer to in the context of electric motors?

Slip in electric motors is defined as the difference between the synchronous speed of the motor and the actual speed of the rotor. Synchronous speed is the speed at which the magnetic field rotates, determined by the frequency of the AC supply and the number of poles in the motor. The rotor, however, usually rotates at a speed slightly less than this due to the need for torque generation; this difference is what we refer to as slip.

In practical terms, slip is an important parameter because it influences the motor's performance characteristics. A certain amount of slip is necessary for torque production in induction motors. If the rotor were to reach synchronous speed, it would not cut through the magnetic field lines and thus would produce no torque, effectively stopping the motor.

Understanding slip is crucial for anyone working with electric motors because it helps in diagnosing motor performance issues and optimizing motor selection for specific applications. The other concepts mentioned, such as the speed at which the motor rotates, the amount of torque produced, and the loss of energy due to friction, while relevant to motor operation, do not encapsulate the definition of slip itself.