Speed Control of DC motor by field resistance control

Which torque is greater.....
The following motor definitely has a permanent magnet rotor.....
To eliminate the fifth harmonic a short-pitched coil should have a short-pitching angle of.....
A full-pitched coil of Ni ampere-turns placed in stator slots causes a fundamental mmf wave of peak amplitude.....
Speed of 3-phase induction motor is controlled from 1 to 2pu using a variable frequency inverter. Equivalent circuit parameter to vary is