Electrical Machines – Multiple Choice Questions (MCQs)

1. 25. What is the function of damper windings in a synchronous machine?

   • A. To provide starting torque
   • B. To suppress hunting
   • C. To reduce armature reaction
   • D. To improve voltage regulation

2. 26. The voltage regulation of an alternator is defined as:

   • A. No-load voltage - full-load voltage / full-load voltage
   • B. No-load voltage - full-load voltage / no-load voltage
   • C. Full-load voltage / no-load voltage
   • D. No-load voltage / full-load voltage

3. 27. The efficiency of a DC machine is determined by:

   • A. Swinburne's test
   • B. Brake test
   • C. Hopkinson's test
   • D. Both Swinburne's and Hopkinson's test

4. 28. What is the main advantage of a brushless DC motor?

   • A. No need for commutation
   • B. Higher efficiency
   • C. Longer lifespan
   • D. All of the above

5. 29. A universal motor can operate on:

   • A. AC only
   • B. DC only
   • C. Both AC and DC
   • D. Neither AC nor DC

6. 30. The core material of a transformer is usually:

   • A. Cast iron
   • B. Aluminum
   • C. Silicon steel
   • D. Copper

7. 31. The leakage flux in a transformer links:

   • A. Primary winding only
   • B. Secondary winding only
   • C. Both primary and secondary windings
   • D. Neither primary nor secondary windings

8. 32. What is the main difference between an ideal transformer and a practical transformer?

   • A. Ideal transformer has no losses
   • B. Ideal transformer has infinite permeability
   • C. Ideal transformer has unity coupling coefficient
   • D. All of the above

9. 33. The voltage regulation of a transformer is zero at:

   • A. Unity power factor
   • B. Leading power factor
   • C. Lagging power factor
   • D. Zero power factor

10. 34. Why is the secondary winding of a current transformer (CT) always short-circuited when not in use?

    • A. To prevent high voltage
    • B. To prevent core saturation
    • C. To protect the CT from damage
    • D. All of the above

11. 35. The speed of a DC series motor is ________ at no load.

    • A. Very high
    • B. Low
    • C. Zero
    • D. Constant

12. 36. Braking of a DC motor can be achieved by:

    • A. Dynamic braking
    • B. Regenerative braking
    • C. Plugging
    • D. All of the above