A. at 0.8 p.f B. at 0.5 p.f c. at zero p.f D. at unity p.f
At zero bcoz At unity power factor, the angle between armature current I and induced emf E, is zero. That means, armature current and induced emf are in same phase. But we know theoretically that emf induced in the armature is due to changing main field flux, linked with the armature conductor.