Electrical Machines – Multiple Choice Questions (MCQs)

1. 73. The phenomenon of 'rotor resistance control' is applicable to:

   • A. Squirrel cage induction motor
   • B. Slip ring induction motor
   • C. Synchronous motor
   • D. DC series motor

2. 74. The efficiency of a DC generator is maximum when:

   • A. Variable losses are equal to constant losses
   • B. Variable losses are greater than constant losses
   • C. Constant losses are greater than variable losses
   • D. There are no losses

3. 75. Which winding of a DC compound motor has maximum number of turns?

   • A. Shunt field winding
   • B. Series field winding
   • C. Armature winding
   • D. Interpole winding

4. 76. The crawling in an induction motor is typically at a speed of about ________ of synchronous speed.

   • A. 1/3
   • B. 1/5
   • C. 1/7
   • D. 1/2

5. 77. A motor used in electric trains is typically a:

   • A. DC shunt motor
   • B. DC series motor
   • C. Synchronous motor
   • D. Induction motor

6. 78. The output of a DC generator is:

   • A. Pure DC
   • B. Pulsating DC
   • C. AC
   • D. Half-wave rectified AC

7. 79. The speed of a DC shunt motor can be controlled by varying the:

   • A. Armature voltage
   • B. Field current
   • C. Both armature voltage and field current
   • D. Applied frequency

8. 80. Which of the following is a non-rotating electrical machine?

   • A. DC motor
   • B. Induction motor
   • C. Transformer
   • D. Alternator

9. 81. The maximum torque in an induction motor occurs at a slip value that depends on:

   • A. Rotor resistance and reactance
   • B. Stator resistance and reactance
   • C. Supply voltage
   • D. Load

10. 82. An induction motor is essentially a:

    • A. Constant speed machine
    • B. Constant torque machine
    • C. Variable speed machine
    • D. Variable torque machine

11. 83. What prevents a synchronous motor from self-starting?

    • A. Absence of starting winding
    • B. Lack of induced EMF in rotor
    • C. Zero starting torque
    • D. Rotor inertia

12. 84. The synchronous impedance method for alternator voltage regulation gives results that are:

    • A. Too high
    • B. Too low
    • C. Accurate
    • D. Dependent on power factor