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MCQOPTIONS
This section includes 244 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens |
| A. | Nothing will happen to the motor |
| B. | This will make armature to take heavy current, possibly burning it |
| C. | This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| D. | Motor will run at very slow speed |
| Answer» D. Motor will run at very slow speed | |
| 52. |
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens |
| A. | This will make armature to take heavy current, possibly burning it |
| B. | This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| C. | Nothing will happen to motor |
| D. | Motor will come to stop |
| Answer» B. This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses | |
| 53. |
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? |
| A. | The motor will stop |
| B. | The motor will continue to run |
| C. | The armature may burn |
| D. | The motor will run noisy |
| Answer» D. The motor will run noisy | |
| 54. |
Which D.C. motor is generally preferred for cranes and hoists? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 55. |
For the same H.P. rating and full load speed, following motor has poor starting torque |
| A. | Shunt |
| B. | Series |
| C. | Differentially compounded |
| D. | Cumulatively compounded |
| Answer» D. Cumulatively compounded | |
| 56. |
At the instant of starting when a D.C. motor is put on supply, it behaves like |
| A. | A highly resistive circuit |
| B. | A low resistance circuit |
| C. | A capacitive circuit |
| D. | None of the above |
| Answer» C. A capacitive circuit | |
| 57. |
Differentially compound D.C. motors can find applications requiring |
| A. | High starting torque |
| B. | Low starting torque |
| C. | Variable speed |
| D. | Frequent on-off cycles |
| Answer» C. Variable speed | |
| 58. |
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be |
| A. | Level compounded |
| B. | Under compounded |
| C. | Cumulatively compounded |
| D. | Differentially compounded |
| Answer» D. Differentially compounded | |
| 59. |
Which motor has the poorest speed control? |
| A. | Differentially compounded motor |
| B. | Cumulatively compounded motor |
| C. | Shunt motor |
| D. | Series motor |
| Answer» E. | |
| 60. |
The direction of rotation of a D.C. series motor can be changed by |
| A. | Interchanging supply terminals |
| B. | Interchanging field terminals |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| Answer» C. Either of (A) and (B) above | |
| 61. |
The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is |
| A. | 4.0 |
| B. | 2.0 |
| C. | 1.0 |
| D. | 0.5 |
| Answer» E. | |
| 62. |
Which of the following motors is most suitable for signalling devices and many kinds of timers ? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Induction motor |
| D. | Reluctance motor |
| Answer» E. | |
| 63. |
Ward-Leonard control is basically a |
| A. | Voltage control method |
| B. | Field diverter method |
| C. | Field control method |
| D. | Armature resistance control method |
| Answer» B. Field diverter method | |
| 64. |
By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor? |
| A. | Frame |
| B. | Shaft |
| C. | Commutator |
| D. | Stator |
| Answer» D. Stator | |
| 65. |
For constant torque drive which speed control method is preferred? |
| A. | Field control |
| B. | Armature voltage control |
| C. | Shunt armature control |
| D. | Mechanical loading system |
| Answer» C. Shunt armature control | |
| 66. |
In a D.C. generator, the iron losses mainly take place in |
| A. | Yoke |
| B. | Commutator |
| C. | Armature conductors |
| D. | Armature rotor |
| Answer» E. | |
| 67. |
In D.C. machines the residual magnetism is of the order of |
| A. | 2 to 3 percent |
| B. | 10 to 15 percent |
| C. | 20 to 25 percent |
| D. | 50 to 75 percent |
| Answer» B. 10 to 15 percent | |
| 68. |
In D.C. machines fractional pitch winding is used |
| A. | To improve cooling |
| B. | To reduce copper losses |
| C. | To increase the generated e.m.f. |
| D. | To reduce the sparking |
| Answer» E. | |
| 69. |
In which of the following applications D.C. series motor is invariably tried? |
| A. | Starter for a car |
| B. | Drive for a water pump |
| C. | Fan motor |
| D. | Motor operation in A.C. or D.C. |
| Answer» B. Drive for a water pump | |
| 70. |
In the D.C. motor the iron losses occur in |
| A. | The field |
| B. | The armature |
| C. | The brushes |
| D. | The commutator |
| Answer» C. The brushes | |
| 71. |
The hysteresis loss in a D.C. machine least depends on |
| A. | Frequency of magnetic reversals |
| B. | Maximum value of flux density |
| C. | Volume and grade of iron |
| D. | Rate of flow of ventilating air |
| Answer» E. | |
| 72. |
Which of the following loss in a D.C. generator is dissipated in the form of heat? |
| A. | Mechanical loss |
| B. | Core loss |
| C. | Copper loss |
| D. | All of the above |
| Answer» E. | |
| 73. |
Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator? |
| A. | Providing laminations in armature core |
| B. | Providing laminations in stator |
| C. | Using nonmagnetic material for frame |
| D. | Using material of low hysteresis coefficient for armature core material |
| Answer» E. | |
| 74. |
To get the speed of D.C, motor below the normal without wastage of electrical energy is used. |
| A. | Ward Leonard control |
| B. | Rheostat control |
| C. | Any of the above method |
| D. | None of the above method |
| Answer» B. Rheostat control | |
| 75. |
In a D.C. shunt motor, speed is |
| A. | Independent of armature current |
| B. | Directly proportional to the armature current |
| C. | Proportional to the square of the current |
| D. | Inversely proportional to the armature current |
| Answer» B. Directly proportional to the armature current | |
| 76. |
The purpose of retardation test on D.C. shunt machines is to find out |
| A. | Stray losses |
| B. | Eddy current losses |
| C. | Field copper losses |
| D. | Windage losses |
| Answer» B. Eddy current losses | |
| 77. |
Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» D. Differentially compounded motor | |
| 78. |
For which types of D.C. motor, dynamic braking is generally used? |
| A. | Shunt motors |
| B. | Series motors |
| C. | Compound motors |
| D. | All of the above |
| Answer» E. | |
| 79. |
Speed control by Ward Leonard method gives uniform speed variation |
| A. | In one direction |
| B. | In both directions |
| C. | Below normal speed only |
| D. | Above normal speed only |
| Answer» C. Below normal speed only | |
| 80. |
In a D.C. generator all of the following could be the effects of iron losses except |
| A. | Loss of efficiency |
| B. | Excessive heating of core |
| C. | Increase in terminal voltage |
| D. | Rise in temperature of ventilating air |
| Answer» D. Rise in temperature of ventilating air | |
| 81. |
During rheostatic braking of D.C. series motors |
| A. | Motor is run as a generator |
| B. | Motor is reversed in direction |
| C. | Motor is run at reduced speed |
| D. | None of these |
| Answer» B. Motor is reversed in direction | |
| 82. |
Which D.C. motor is preferred for elevators? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential compound motor |
| D. | Cumulative compound motor |
| Answer» E. | |
| 83. |
Starters are used with D.C. motors because |
| A. | These motors have high starting torque |
| B. | These motors are not self-starting |
| C. | Back e.m.f. of these motors is zero initially |
| D. | To restrict armature current as there is no back e.m.f. while starting |
| Answer» E. | |
| 84. |
The armature voltage control of D.C. motor provides |
| A. | Constant torque drive |
| B. | Constant voltage drive |
| C. | Constant current drive |
| D. | None of the above |
| Answer» B. Constant voltage drive | |
| 85. |
The speed of a D.C. shunt motor can be increased by |
| A. | Increasing the resistance in armature circuit |
| B. | Increasing the resistance in field circuit |
| C. | Reducing the resistance in the field circuit |
| D. | Reducing the resistance in the armature circuit |
| Answer» C. Reducing the resistance in the field circuit | |
| 86. |
Which method of braking is generally used in elevators?~! |
| A. | Plugging |
| B. | Regenerative braking |
| C. | Rheostat braking |
| D. | None of the above |
| Answer» B. Regenerative braking | |
| 87. |
Which of the following motor is preferred for operation in highly explosive atmosphere? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Air motor |
| D. | Battery operated motor |
| Answer» D. Battery operated motor | |
| 88. |
Which of the following motor is preferred for operation in highly explosive atmosphere?~! |
| A. | Series motor |
| B. | Shunt motor |
| C. | Air motor |
| D. | Battery operated motor |
| Answer» D. Battery operated motor | |
| 89. |
Starters are used with D.C. motors because%! |
| A. | These motors have high starting torque |
| B. | These motors are not self-starting |
| C. | Back e.m.f. of these motors is zero initially |
| D. | To restrict armature current as there is no back e.m.f. while starting |
| Answer» E. | |
| 90. |
By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?%! |
| A. | Frame |
| B. | Shaft |
| C. | Commutator |
| D. | Stator |
| Answer» D. Stator | |
| 91. |
The speed of a D.C. shunt motor more than its full-load speed can be obtained by%! |
| A. | Decreasing the field current |
| B. | Increasing the field current |
| C. | Decreasing the armature current |
| D. | Increasing the armature current |
| Answer» B. Increasing the field current | |
| 92. |
The condition for maximum power in case of D.C. motor is%! |
| A. | Back e.m.f. = 2 √ó supply voltage |
| B. | Back e.m.f. = I √ó supply voltage |
| C. | Supply voltage =I √ó back e.m.f. |
| D. | Supply voltage = back e.m.f. |
| Answer» C. Supply voltage =I ‚àö√≥ back e.m.f. | |
| 93. |
Which of the following motors one will choose to drive the rotary compressor?%! |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Universal motor |
| D. | Synchronous motor |
| Answer» E. | |
| 94. |
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%! |
| A. | Series motor |
| B. | Shunt motor |
| C. | Compound motor |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 95. |
Which D.C. motor has got maximum self relieving property?%! |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 96. |
For starting a D.C. motor a starter is required because%! |
| A. | It limits the speed of the motor |
| B. | It limits the starting current to a safe value |
| C. | It starts the motor |
| D. | None of the above |
| Answer» C. It starts the motor | |
| 97. |
D.C. generators are installed near the load centers to reduce%! |
| A. | Iron losses |
| B. | Line losses |
| C. | Sparking |
| D. | Corona losses |
| Answer» C. Sparking | |
| 98. |
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%! |
| A. | Series motor |
| B. | Shunt motor |
| C. | Compound motor |
| D. | Any of the above |
| Answer» B. Shunt motor | |
| 99. |
In D.C. shunt motors as load is reduced%! |
| A. | The speed will increase abruptly |
| B. | The speed will increase in proportion to reduction in load |
| C. | The speed will remain almost/constant |
| D. | The speed will reduce |
| Answer» D. The speed will reduce | |
| 100. |
The main disadvantage of the Ward-Leonard control method is%! |
| A. | High initial cost |
| B. | High maintenance cost |
| C. | Low efficiency at high loads |
| D. | All of the above |
| Answer» E. | |