DC MACHINES 6

 

DC MACHINES MCQ 6

 

1. The speed of d.c. series motor decreases if the flux in the field winding
a) remains constant
b) increases
c) decrease
d) None of the above.
ans. b

2. Which of the following motors is used to drive the constant speed line shafting lathes, blowers and fans?
a) D.C .shunt motor
b) D.C. series motor
c) Commutative compound motor.
d) None of these
ans. a

3. If the back emf is a d.c. motor is absent , then
a) motor will run at very high speed.
b) motor will run at very low speed.
c) motor will not run at all.
d) motor will burn.
ans. d

4. The field flux of a d.c. motor can be controlled to achieve
a) The speeds lowers than rated speed.
b) The speeds higher than rated speed.
c) the speeds at rated speed
d) None of the above .
ans. b

5. By providing a variable resistance across the series field in a d.c. series motor, speeds above normal can be obtained because
a) armature current decreases
b) flux is reduced
c) line current is decreased
d) None of these
ans. b

6. For which of the following dc motors is the typical field of application mentioned?
a) shunt motor - electric trains
b) series motor - machine tools
c) series motor - belt drive
d) compound motor - fly wheel drive
ans. d

7. The generator of a power station produces an electric pressure by
a) conversion point
b) magnetic induction
c) conversion of light
d) mechanical pressure
ans. d

8. Why is the air gap between stator and armature of an electric motor kept as small as possible?
a) To get stronger magnetic field
b) To make the rotation easier.
c) To reach a higher speed of rotation.
d) To improve the air circulation.
ans. a

9. Which of the following types of generators gives constant voltage output at all loads?
a) series generator
b) shunt generator
c) short shunt compound generator
d) level compound generator
ans. d

10. Interpoles are meant for
a) increasing the speed of the motor
b) decreasing counter emf
c) reducing sparking at the commutator.
d) converting armature current to dc.
ans. c

  Click To Read More DC Machine MCQ :  DC Machine