Torque Production

While alternating current is applied to the stator windings of an AC induction motor, and a rotating magnetic field is established.  A rotating magnetic field cuts the bars of the rotor and induces a current within them due to generator action. The direction of this current flow could be found by using the left-hand rule for generators. That induced current will generates a magnetic   field,  opposite in polarity of the stator field, around the conductors of the rotor that will try to line up along with the magnetic field of the stator.  Because the stator field is rotating continuously, the rotor cannot line up with or lock onto the stator field and, thus must follow behind it that was show in the above figure.

Figure: Induction Motor