1030234110 - Electrical Machines – II STUDY MATERIALS

 

1030234110 - Electrical Machines – II

 

20 MARKS MODEL MCQ TEST LINK CLICK TO ATTEND TEST

 

 

PART A

1.      Which of the following is an advantage of the rotating field in alternators?
 a) It reduces the mechanical wear on the rotor
b) It simplifies the construction of the stator
c) It allows for higher power factor operation
d) It eliminates the need for excitation

 

2. The frequency of generated EMF in an alternator depends on:
    a) Speed and number of poles
   b) Armature current
   c) Field current
   d) Load

3. In alternators, the rotating part is usually the:
    a) Field system
   b) Armature
   c) Core
   d) Commutator

4. What is the primary difference between single-layer and double-layer windings in alternators?
   a) Single-layer windings have more turns per coil
    b) Double-layer windings are more efficient in reducing harmonics
   c) Single-layer windings are used for high-speed alternators
   d) Double-layer windings are more compact but less efficient

5. What is the primary cause of a change in terminal voltage of an alternator under varying load conditions?
   a) Variation in armature current
   b) Change in synchronous reactance
    c) Effect of armature reaction
   d) External voltage fluctuations

6. Which of the following methods is used to determine the voltage regulation of an alternator by the indirect method?
   a) Direct load test
    b) EMF method
   c) Parallel operation
   d) Synchronizing method

7. In the context of alternators, what is the meaning of the term Infinite Bus Bar?
    a) A power source with unlimited capacity for load sharing
   b) A system where alternators share the load equally
   c) A theoretical concept where the voltage remains constant regardless of load changes
   d) A device that helps synchronizes multiple generators automatically

8. Which method is used to synchronize alternators based on the lamp brightness variation?
   a) Dark Lamp Method
   b) Bright Lamp Method
    c) Dark-Bright Lamp Method
   d) Synchroscope Method

9. The working principle of induction motor is based on:
    a) Electromagnetic induction
   b) Mutual induction
   c) Faraday’s law
   d) Self-induction

10. The speed of an induction motor is given by:
     a) Ns(1–s)
    b) Ns(1+s)
    c) Ns/s
    d) Ns/s²

11. What is the characteristic behavior of the slip-torque curve in an induction motor?
    a) The torque increases linearly with slip
    b) The torque decreases with increasing slip
     c) There is a maximum torque at a certain slip value, beyond which the torque decreases
    d) The torque remains constant regardless of the slip

12. What is the purpose of the auto transformer starter for an induction motor?
    a) To provide a higher starting torque
     b) To reduce the starting current by providing reduced voltage
    c) To synchronize the motor with the power supply
    d) To prevent cogging and crawling

13. The starting torque of a single-phase induction motor is:
     a) Zero
    b) Maximum
    c) Equal to running torque
    d) Constant

14. Capacitor start motors are used for:
    a) High starting torque
    b) Low cost
    c) Low starting torque
    d) Speed regulation

15. In a shaded pole motor, shading coil produces:
     a) Rotating magnetic field
    b) Constant field
    c) Alternating field
    d) Zero torque

16. Repulsion motor works on the principle of:
    a) Induction
     b) Repulsion between currents
    c) Electromagnetic attraction
    d) Magnetic repulsion

17. In a synchronous motor, the speed is:
     a) Constant
    b) Variable
    c) Depends on load
    d) Proportional to voltage

18. Hunting in synchronous motor is caused by:
     a) Sudden load changes
    b) Constant load
    c) Voltage drop
    d) Excitation fault

19. A synchronous condenser is used for:
     a) Power factor correction
    b) Voltage regulation
    c) Speed control
    d) Load balancing

20. Damper windings in a synchronous motor are used to:
     a) Prevent hunting
    b) Reduce torque
    c) Increase current
    d) Increase speed