41. 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
42. 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
43. 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
44. 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
45. 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
46. D.C. series motors are best suited for traction work because
a) torque is proportional to the square of armature current and speed is inversely proportional to torque.
b) torque is proportional to the square of armature current and speed is proportional to the torque.
c) torque and speed are proportional to square of armature current.
d) none of these
ans. a
47. A series motor is started without load. The effect is that
a) the torque increases rapidly
b) the speed increases rapidly
c) current drawn increases rapidly
d) the back emf decreases.
ans. b
48. The direction of rotation of a dc series motor can be reversed by interchanging
a) the supply terminals only
b) the field terminals only
c) the supply as well as field terminals
d) None of these.
ans. b
49. The motor used for intermittent, high torque load is
a) dc shunt motor
b) dc series motor
c) differential compound motor
d) cumulative compound motor
ans. d
50. If the field of a dc shunt motor is opened.
a) it will continue to run at its rated speed.
b) the speed of the motor will become very high
c) the motor will stop
d) the speed of motor will decrease.
ans. b
a) remains constant
b) increases
c) decrease
d) None of the above.
ans. b
42. 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
43. 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
44. 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
45. 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
46. D.C. series motors are best suited for traction work because
a) torque is proportional to the square of armature current and speed is inversely proportional to torque.
b) torque is proportional to the square of armature current and speed is proportional to the torque.
c) torque and speed are proportional to square of armature current.
d) none of these
ans. a
47. A series motor is started without load. The effect is that
a) the torque increases rapidly
b) the speed increases rapidly
c) current drawn increases rapidly
d) the back emf decreases.
ans. b
48. The direction of rotation of a dc series motor can be reversed by interchanging
a) the supply terminals only
b) the field terminals only
c) the supply as well as field terminals
d) None of these.
ans. b
49. The motor used for intermittent, high torque load is
a) dc shunt motor
b) dc series motor
c) differential compound motor
d) cumulative compound motor
ans. d
50. If the field of a dc shunt motor is opened.
a) it will continue to run at its rated speed.
b) the speed of the motor will become very high
c) the motor will stop
d) the speed of motor will decrease.
ans. b
