Electrical Machines – Multiple Choice Questions (MCQs)

1. 37. The field winding of a DC shunt motor is connected in ________ with the armature.

   • A. Series
   • B. Parallel
   • C. Series-parallel
   • D. Star

2. 38. Which type of DC motor is preferred for traction applications?

   • A. Shunt motor
   • B. Series motor
   • C. Compound motor
   • D. Permanent magnet motor

3. 39. The armature reaction in a DC machine causes:

   • A. Flux distortion
   • B. Demagnetization
   • C. Cross-magnetization
   • D. All of the above

4. 40. The process of changing AC to DC in a DC generator is called:

   • A. Rectification
   • B. Inversion
   • C. Commutation
   • D. Regulation

5. 41. A 3-phase induction motor with 4 poles is supplied from a 50 Hz supply. The synchronous speed will be:

   • A. 1000 rpm
   • B. 1500 rpm
   • C. 750 rpm
   • D. 3000 rpm

6. 42. The power factor of an induction motor at light load is generally:

   • A. High
   • B. Low
   • C. Unity
   • D. Zero

7. 43. Rotor of a squirrel cage induction motor is typically made of:

   • A. Copper bars
   • B. Aluminum bars
   • C. Steel laminations
   • D. Carbon brushes

8. 44. The back EMF in a DC motor is proportional to:

   • A. Armature current
   • B. Field flux and speed
   • C. Applied voltage
   • D. Load torque

9. 45. The main function of brushes in a DC machine is to:

   • A. Collect current from commutator
   • B. Provide excitation
   • C. Reduce sparks
   • D. Clean the commutator

10. 46. The torque developed by a DC motor is directly proportional to:

    • A. Armature current
    • B. Field flux
    • C. Both armature current and field flux
    • D. Speed

11. 47. A step-up transformer has turns ratio N2/N1:

    • A. < 1
    • B. = 1
    • C. > 1
    • D. Independent of 1

12. 48. The rating of a transformer is usually expressed in:

    • A. kW
    • B. kVA
    • C. kVAR
    • D. Joules