D.C. motor

Which D.C. motor has got maximum self relieving property ?(a) Series motor(6) Shunt motor(c) Cumulatively compounded motor(d) Differentially compounded motor121. In the D.C. motor the iron losses occur in(a) the field(b) the armature(c) the brushes(d) the commutatorThe speed of a D.C. shunt motor is required to be more than full load speed. This ispossible by(a) reducing the field current(b) decreasing the armature current(c) increasing the armature current(d) increasing the excitation current(e) none of the above methods