DC Motors Quizzes | Trivia Quiz for Practice

76. For a D.C. shunt motor if the excitation is changed

1. torque will remain constant
2. torque will change but power will remain constant
3. torque and power both will change
4. torque, power and speed, all will change

77. For constant torque drive which speed control method is preferred ?

1. Field control
2. Armature voltage control
3. Shunt armature control
4. Mechanical loading system

78. For starting a D.C. motor a starter is required because

1. it limits the speed of the motor
2. it limits the starting current to a safe value
3. it starts the motor
4. none of the above

79. For the same H.P. rating and full load speed, following motor has poor starting torque

1. shunt
2. series
3. differentially compounded
4. cumulativelycompounded

80. For which of the following applications a D.C. motor is preferred over an A.C. motor ?

1. Low speed operation
2. High speed operation
3. Variable speed operation
4. Fixed speed operation

81. For which types of D.C. motor, dynamic braking is generally used ?

1. Shunt motors
2. Series motors
3. Compound motors
4. All of the above

82. Hopkinsons test on D.C. machines is conducted at

1. no-load
2. part load
3. full-load
4. overload

83. If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor

1. of lower H.P. should be selected
2. of higher H.P. should be selected
3. can be used for 50°C ambient temperature also
4. is to be derated by a factor recom-mended by manufacturer and select the next higher H.P. motor

84. If a D.C. motor is connected across the A.C. supply it will

1. run at normal speed
2. not run
3. run at lower speed
4. burn due to heat produced in the field winding by .eddy currents

85. If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ?

1. Series motor
2. Shunt motor
3. Differentially compound motor
4. Cumulative compound motor

86. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens

1. this will make armature to take heavy current, possibly burning it
2. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
3. nothing will happen to motor
4. motor will come to stop

87. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens

1. nothing will happen to th£ motor
2. this will make armature to take heavy current, possibly burning it
3. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
4. motor will run at very slow speed

88. If I2 be the armature current, then speed of a D.C. shunt motor is

1. independent of Ia
2. proportional to la
3. varies as (Ia)
4. varies as la

89. If the field of a D.C. shunt motor gets opened while motor is running

1. the speed of motor will be reduced %
2. the armature current will reduce
3. the motor will attain dangerously high speed 1
4. the motor will continue to nuvat constant speed

90. If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will

1. increase
2. decrease
3. remain same
4. become zero