(a) Explain and describe why and how space heaters are fitted to motors. (6)

(b) Give a clear explanation of the following effects in a three phase induction motor,

(i) the production of rotating field,

(ii) the presence of an induced rotor current,

(iii) the development of torque.

A 4-pole, 250V motor has its armature removed in order to test the continuity of the field windings which are connected in series and consist of 2000 turns each. What is the average e.m.f. induced when the current is switched off, if the flux falls from 0.026Wb to 0.001 Wb in 0.2s? (10)