The inductance of a phase winding of a three-phase salient-pole motor is measured to be of the form L (θm) = L0 + L2 cos 2θm where θm is the angular position of the rotor.

a. How many poles are on the rotor of this motor?

b. Assuming that all other winding currents are zero and that this phase is excited by a constant current I0, find the torque Tfld (θ) acting on the rotor.