31. The power stated on the name plate of any motor is always
a) the output power at the shaft.
b) the power drawn in kVA.
c) the power drawn in kW.
d) the gross power.
ans. a
32. The exciting coils of any d.c. machine are wound
a) in the machine
b) in the armature slots
c) around the poles
d) separately
ans. c
33. A starter is necessary to start a d.c. motor because
a) it starts the motor.
b) it limits the speed of the motor.
c) it limits the back emf to a safe value.
d) it limits the starting current to a safe value.
ans. d
34. The efficiency of any electrical machine will be high , if
a) its losses are minimum.
b) its losses are more.
c) voltage applied is constant.
d) the current drawn is minimum.
ans. a
35. The direction of rotation of a d.c. shunt motor is reversed by
a) reversing armature connections.
b) interchanging the armature and field connection.
c) adding resistance to the field circuit.
d) reversing supply connections.
ans. a
36. The armature of d.c.motors is laminated
a) to reduce the hysteresis losses.
b) to reduce the eddy current losses.
c) to reduce the inductivity of armature.
d) to reduce the mass of the armature.
ans. b
37. Which of the following is a correct statement about a series motor?
a) Its field winding consists of thicker wire and less turns.
b) It can run easily without load.
c) It has almost constant speed.
d) It has poor torque.
ans. a
38. Which of the following d.c. motors has the least drop in the speed between no load to nominal load?
a) Shunt motor with commutating poles.
b) Series motor without commutating poles.
c) Compound motor without commutating poles.
d) Series motor with commutating poles.
ans. a
39. What happens if the field winding of a running shunt motor suddenly breaks open?
a) Its speed slows down
b) Its speed becomes dangerously high.
c) It gives out sparks.
d) It stops at once.
ans. b
40. The speed of a series motor at no load is
a) zero
b) 3000 rpm.
c) 3600 rpm.
d) infinity.
ans. d
a) the output power at the shaft.
b) the power drawn in kVA.
c) the power drawn in kW.
d) the gross power.
ans. a
32. The exciting coils of any d.c. machine are wound
a) in the machine
b) in the armature slots
c) around the poles
d) separately
ans. c
33. A starter is necessary to start a d.c. motor because
a) it starts the motor.
b) it limits the speed of the motor.
c) it limits the back emf to a safe value.
d) it limits the starting current to a safe value.
ans. d
34. The efficiency of any electrical machine will be high , if
a) its losses are minimum.
b) its losses are more.
c) voltage applied is constant.
d) the current drawn is minimum.
ans. a
35. The direction of rotation of a d.c. shunt motor is reversed by
a) reversing armature connections.
b) interchanging the armature and field connection.
c) adding resistance to the field circuit.
d) reversing supply connections.
ans. a
36. The armature of d.c.motors is laminated
a) to reduce the hysteresis losses.
b) to reduce the eddy current losses.
c) to reduce the inductivity of armature.
d) to reduce the mass of the armature.
ans. b
37. Which of the following is a correct statement about a series motor?
a) Its field winding consists of thicker wire and less turns.
b) It can run easily without load.
c) It has almost constant speed.
d) It has poor torque.
ans. a
38. Which of the following d.c. motors has the least drop in the speed between no load to nominal load?
a) Shunt motor with commutating poles.
b) Series motor without commutating poles.
c) Compound motor without commutating poles.
d) Series motor with commutating poles.
ans. a
39. What happens if the field winding of a running shunt motor suddenly breaks open?
a) Its speed slows down
b) Its speed becomes dangerously high.
c) It gives out sparks.
d) It stops at once.
ans. b
40. The speed of a series motor at no load is
a) zero
b) 3000 rpm.
c) 3600 rpm.
d) infinity.
ans. d
