21. In dc machines, the armature windings are placed on the rotor because of the necessity for
- electromechanical energy conversion
- generation of voltage
- commutation
- development of torque
22. Wave winding is employed in a dc machine of
- high current and low voltage rating
- low current and high voltage rating
- high current and high voltage rating
- low current and low voltage rating
23. In lap winding, the number of brushes is always _______ the number of poles.
- double
- same as
- half
- none of these
24. A 4-pole generator with 16 coils has a two layer lap winding. The pole pitch is
- 32
- 16
- 8
- 4
25. Welding generator will have
- lap winding
- wave winding
- either lap or wave winding
- none of these
26. If in a 6-pole lap wound dc machine, the air gap under each pole is not the same, this is likely to result in
- higher terminal voltage
- reduced eddy currents
- unequal current in parallel paths
- none of these
27. The number of parallel paths for a 4-pole duplex lap winding will be
- 2
- 4
- 6
- 8
28. Width of the carbon brush should be equal to
- less than the width of one commutator segment
- the width of 1 to 2 commutator segments
- the width of 2 to 3 commutator segments
- the width of more than 3 commutator segments
29. Wave winding is composed of
- any odd number of conductors
- any even number of conductors
- that even number which is exact multiple of poles ±2
- that even number which is exact multiple of poles
30. For a 4-pole machine, wave winding is impossible with _____ armature conductors.
- 30
- 32
- 34
- 38
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