Electrical Machines Multiple Choice Questions and Answers for Practice

16. Inter poles in DC machines are provided to reduce

1. Sparking
2. Armature reaction
3. Iron loss
4. Efficiency

17. DC motor yoke is generally made of

1. Wood
2. Copper
3. Aluminum
4. Steel

18. The output of a rotating electrical machine is limited by

1. Size of the machine
2. Peripheral velocity
3. Temperature rise
4. None of the above

19. The dimensions of a dc machine primarily depend on

1. kW output
2. Work done per revolution
3. Exposed surface
4. None of the above

20. Skewing of rotor slots helps in

1. Improving beat transfer
2. Reducing noise
3. Suppressing undesirable harmonics
4. all of the above

21. The harmonics in rotating machines are generated due to

1. Non-sinusoidal field form
2. Slotting of the stator core
3. Both (A) and (B) above
4. None of the above

22. The effect of harmonics in rotating machines can be minimized by

1. Use of longer air gap
2. Skewing the poles
3. Use of distributed winding
4. all of the above

23. In dc machines the number of poles is generally decided by

1. Frequency of flux reversals
2. Weight of iron parts
3. Weight of copper
4. all of the above

24. In dc machines by increasing the number of poles, all of the following reduce except:

1. Weight of copper
2. Weight of iron parts
3. Frequency of flux reversals
4. Overall size of the machine