DC Motor or Direct Current Motor Multiple Choice Questions and Answers
16. A DC motor can be looked upon as a DC generator with the power flow .......
A.Reduced
B.Reversed
C.Increased
D.Modified
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B.Reversed
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17. To have sparkless commutation the armature reaction in a DC machine is neutralised by .......
A.Using compensating windings and commutating polls
B.Shifting the brush axis from the geometrical neutral axis to the magnetic neutral axis
C.Fixing the brush axis in alignment with the main pole axis
D.Increasing the field excitation
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18. The armature winding of dc machine is made up of a number of coils distributed in a large number of armature slots instead of placing all the coils into slots to.........
A.Get sinusoidal emf at the output terminals
B.Have minimum heat dissipation from the armature
C.Make the armature dynamically balanced
C.Get maximum generated emf in the armature
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19. In a DC motor,the mechanical output power actually comes from ......
A.Field system
B.Air-gap flux
C.Back emf
D.Electrical input power
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20. If the pole flux of a DC motor approaches zero,its speed will .......
A.Approach zero
B.Approach infinity
C.No change due to the corresponding change in back emf
D.Approach is stable value somewhere between zero and infinity
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