DC Motors Objective Questions | MCQ Quiz for Practice

61. As -the load is increased the speed of D.C. shunt motor will

1. reduce slightly
2. increase slightly
3. increase proportionately
4. remains unchanged

62. As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit

1. a resistance is connected in series with armature
2. a resistance is connected parallel to the armature
3. armature is temporarily open circuited
4. a high value resistor is connected across the field winding

63. At the instant of starting when a D.C. motor is put on supply, it behaves like

1. a highly resistive circuit
2. a low resistance circuit
3. a capacitive circuit
4. none of the above

64. Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of

1. D.C. series motor
2. D.C. shunt motor
3. induction motor
4. all of above motors

65. By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

1. Frame
2. Shaft
3. Commutator
4. Stator

66. D.C. generators are installed near the load centres to reduce

1. iron losses
2. line losses
3. sparking
4. corona losses

67. D.C. generators are normally designed for maximum efficiency around

1. full-load
2. rated r.p.m.
3. rated voltage
4. all of the above

68. D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this

1. series motor
2. shunt motor
3. compound motor
4. any of the above

69. D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the

1. series motor
2. shunt motor
3. compound motor
4. any of the above

70. D.C. series motors are used

1. where load is constant
2. where load changes frequently
3. where constant operating speed is needed
4. in none of the above situations.

71. D.C. shunt motors are used for driving

1. trains
2. cranes
3. hoists
4. machine tools

72. Differentially compound D.C. motors can find applications requiring

1. high starting torque
2. low starting torque
3. variable speed
4. frequent on-off cycles

73. During rheostat braking of D.C. series motors

1. motor is run as a generator
2. motor is reversed in direction
3. motor is run at reduced speed

74. Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be

1. level compounded
2. under compounded
3. cumulatively compounded
4. differentially compounded

75. Following motor is used where high starting torque and wide speed range control is required.

1. Single phase capacitor start
2. Induction motor
3. Synchronous motor
4. D.C. motor