_________ is the difference between the field of the stator and the mechanical rotating speed of the rotor.

_________ is the difference between the field of the stator and the mechanical rotating speed of the rotor.

• A. Torque
• B. Slip
• C. Power
• D. Frequency

Answer: (B)

Slip is the difference between the speed of the stator’s rotating magnetic field and the rotor’s actual mechanical speed. The stator field turns at synchronous speed, determined by the supply frequency and the motor’s pole count. The rotor follows but always lags a bit, creating the relative motion that induces rotor currents and produces torque. This lag is expressed as s = (Ns − Nr)/Ns, where Ns is the synchronous speed and Nr is the rotor speed. If there were no slip (Nr equal to Ns), there’d be no induced current in the rotor and no torque, which is why some slip is necessary for operation. In practice, slip is a small percentage under light load and increases as load rises, affecting rotor speed and torque. The other terms—torque (the twisting force), power (energy per time), and frequency (the rate of the supply) —describe different aspects and are not the measure of this speed difference.

Slip is the difference between the speed of the stator’s rotating magnetic field and the rotor’s actual mechanical speed. The stator field turns at synchronous speed, determined by the supply frequency and the motor’s pole count. The rotor follows but always lags a bit, creating the relative motion that induces rotor currents and produces torque. This lag is expressed as s = (Ns − Nr)/Ns, where Ns is the synchronous speed and Nr is the rotor speed. If there were no slip (Nr equal to Ns), there’d be no induced current in the rotor and no torque, which is why some slip is necessary for operation. In practice, slip is a small percentage under light load and increases as load rises, affecting rotor speed and torque. The other terms—torque (the twisting force), power (energy per time), and frequency (the rate of the supply) —describe different aspects and are not the measure of this speed difference.