MCQOPTIONS
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MCQOPTIONS
This section includes 244 Mcqs, each offering curated multiple-choice questions to sharpen your Power Electronics knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
DC motor are still preferred for use in |
| A. | Electric excavators, steel mills and cranes |
| B. | Lathes and machine tools |
| C. | Flour Mills and Jaw crushers |
| D. | Paper industry |
| Answer» B. Lathes and machine tools | |
| 52. |
Hot bearings of a DC motor may be caused by |
| A. | Poor ventilation |
| B. | Incorrect voltage |
| C. | Loose coupling |
| D. | Lack of or dirty lubricant |
| Answer» E. | |
| 53. |
The return circuit for tramcars is through |
| A. | neutral wire |
| B. | rails |
| C. | cables |
| D. | common earthing |
| Answer» C. cables | |
| 54. |
The rate of acceleration on suburban orurban services is restricted by theconsideration of |
| A. | Engine power |
| B. | Track curves |
| C. | Passenger Discomfort |
| D. | Track size |
| Answer» E. | |
| 55. |
The output of the Solar panel is DC. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» B. False | |
| 56. |
The equilibrium speed of a motor load system is obtained |
| A. | when motor torque equals the load torque |
| B. | when motor torque is less than the load torque |
| C. | when motor torque is more than the load torque |
| D. | none of the these. |
| Answer» B. when motor torque is less than the load torque | |
| 57. |
The efficiency of reluctance motor is around |
| A. | 95% |
| B. | 90% |
| C. | 75 to 85% |
| D. | 60 to 75%. |
| Answer» E. | |
| 58. |
the value of the frequency of the DC supply. |
| A. | 0 Hz |
| B. | 50 Hz |
| C. | 20 Hz |
| D. | 10 Hz |
| Answer» B. 50 Hz | |
| 59. |
Which of the following motors has series characteristics ? |
| A. | Shaded pole motor |
| B. | Repulsion motor |
| C. | Capacitor start motor |
| D. | None of the above |
| Answer» C. Capacitor start motor | |
| 60. |
Which of the following devices should be used as a switch for high power and highvoltage application? |
| A. | GTO |
| B. | MOSFET |
| C. | TRIAC |
| D. | Thyristor |
| Answer» E. | |
| 61. |
Centrifugal pumps are usually driven by |
| A. | dc shunt motors |
| B. | dc series motors |
| C. | squirrel cage induction motors |
| D. | any of the above. |
| Answer» D. any of the above. | |
| 62. |
In overhead traveling cranes |
| A. | continuous duty motors are used |
| B. | slow speed motors are preferred |
| C. | short time rated motors arc preferred |
| D. | none of the above. |
| Answer» D. none of the above. | |
| 63. |
The diameter of the rotor shaft for an electric motor depends on which of thefollowing ? |
| A. | r.p.m. only |
| B. | Horse power only |
| C. | Horse power and r.p.m. |
| D. | Horse power, r.p.m. and power factor |
| Answer» D. Horse power, r.p.m. and power factor | |
| 64. |
.............method of starting a three phase induction motor needs six terminals |
| A. | Resistance starting |
| B. | Auto transformer |
| C. | None of the above |
| D. | Star delta |
| Answer» B. Auto transformer | |
| 65. |
In case of contactors, the duty in which the main contacts remain closed for a period bearing a definition relation to the no-load periods, is known as |
| A. | Standard duty |
| B. | Intermittent duty |
| C. | Temporary duty |
| D. | Un-interrupted duty. |
| Answer» C. Temporary duty | |
| 66. |
Which of the following pair is used for frequency converters ? |
| A. | Squirrel cage induction motor and synchronous motor |
| B. | Wound rotor induction motor and synchronous motor |
| C. | Wound rotor induction motor and squirrel cage induction motor |
| D. | Any of the above. |
| Answer» B. Wound rotor induction motor and synchronous motor | |
| 67. |
The selection of control gear for a particular application is based on the consideration of |
| A. | duty |
| B. | starting torque |
| C. | limitations on starting current |
| D. | all of the above. |
| Answer» E. | |
| 68. |
Effect of friction torque is more pronounced |
| A. | when the drive is running on full speed |
| B. | when the drive is being started |
| C. | when the drive is being stopped |
| D. | when the drive at half of its normal speed. |
| Answer» C. when the drive is being stopped | |
| 69. |
For which of the following locomotives the maintenance requirements are theleast? |
| A. | Steam locomotives |
| B. | Diesel locomotives |
| C. | Electric locomotives |
| D. | Equal in all of the above |
| Answer» C. Electric locomotives | |
| 70. |
Rotor of a motor is usually supported on bearings. |
| A. | ball or roller |
| B. | needle |
| C. | bush |
| D. | thrust |
| Answer» B. needle | |
| 71. |
Motor preferred for kiln drives is usually |
| A. | slip ring induction motor |
| B. | three phase shunt wound commutator motor |
| C. | cascade controlled ac motor |
| D. | any of the above. |
| Answer» E. | |
| 72. |
Word Leonard controlled DC Drives are generally used for..... excavators |
| A. | Light duty |
| B. | Medium duty |
| C. | Heavy duty |
| D. | All of the above |
| Answer» D. All of the above | |
| 73. |
For a particular application the type of electric-and control gear are determined bywhich of the following considerations ? |
| A. | Starting torque |
| B. | Conditions of environment |
| C. | Limitation on starting current |
| D. | All of the above |
| Answer» E. | |
| 74. |
When a bogie negotiates a curve, reduction in adhesion occurs resulting in sliding.Thus sliding is acute when |
| A. | wheel base of axles is more |
| B. | degree of curvature is more |
| C. | both (A) and (B) |
| D. | none of the above |
| Answer» D. none of the above | |
| 75. |
Which feature, while selecting a.motor for centrifugal pump, will be of leastsignificance ? |
| A. | Starting characteristics |
| B. | Operating speed |
| C. | Horse power |
| D. | Speed control |
| Answer» E. | |
| 76. |
An elevator Drive is required to operate in |
| A. | One quadrant only |
| B. | Two quadrants |
| C. | Three quadrants |
| D. | Four quadrants |
| Answer» E. | |
| 77. |
method can bring the locomotive to dead stop. |
| A. | Plugging braking |
| B. | Rheostatic braking |
| C. | Regenerative braking |
| D. | None of the above |
| Answer» B. Rheostatic braking | |
| 78. |
The advantage of a synchronous motor in addition to its constant speed is |
| A. | high power factor |
| B. | better efficiency |
| C. | lower cost |
| D. | all of the above. |
| Answer» B. better efficiency | |
| 79. |
What type of force handles for active torques? |
| A. | Strong nuclear forces |
| B. | Weak nuclear forces |
| C. | Gravitational forces |
| D. | Electrostatic forces |
| Answer» D. Electrostatic forces | |
| 80. |
15 minute rated motors are suitable for |
| A. | Light duty cranes |
| B. | Medium duty cranes |
| C. | Heavy duty cranes |
| D. | All of the above |
| Answer» B. Medium duty cranes | |
| 81. |
motor is a constant speed motor. |
| A. | Synchronous motor |
| B. | Schrage motor |
| C. | Induction motor |
| D. | Universal motor |
| Answer» B. Schrage motor | |
| 82. |
In case of centrifugal pumps the starting torque is generally |
| A. | double the running torque |
| B. | slightly more than running torque |
| C. | same as running torque |
| D. | less than running torque. |
| Answer» E. | |
| 83. |
Which of the following happens when start Delta starter is used ? |
| A. | Starting voltage is reduced |
| B. | Starting current is reduced |
| C. | None of the above |
| D. | Both A and B |
| Answer» E. | |
| 84. |
In tramways which of the following motors is used ? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | A.C. three phase motor |
| D. | AC. single phase capacitor start motor |
| Answer» C. A.C. three phase motor | |
| 85. |
In........ method of starting three phase induction motors the starting voltage is not reduced |
| A. | Auto transformer |
| B. | Star Delta |
| C. | Slip ring |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 86. |
By the use of which of the followingm D.C. can be obtained from AC? |
| A. | Silicon diodes |
| B. | Mercury arc rectifier |
| C. | Motor generator set |
| D. | Any of the above |
| Answer» E. | |
| 87. |
Which one is an example of variable loss? |
| A. | Windage loss |
| B. | Hysteresis loss |
| C. | Armature copper loss |
| D. | Friction loss |
| Answer» D. Friction loss | |
| 88. |
Which of the following motors is preferred when quick speed reversal is the mainconsideration? |
| A. | Squirrel cage induction motor |
| B. | Wound rotor induction motor |
| C. | Synchronous motor |
| D. | DC motor |
| Answer» E. | |
| 89. |
Light duty cranes are generally used in |
| A. | Power houses |
| B. | . Pumping stations |
| C. | Auto mobile workshops |
| D. | All of the above |
| Answer» E. | |
| 90. |
Which electromagnet is preferred for noiseless operation |
| A. | DC operated |
| B. | AC operated |
| C. | Any of the above. |
| D. | all |
| Answer» B. AC operated | |
| 91. |
The motor enclosure used for industrial purposes is |
| A. | Protected type |
| B. | Drip proof type |
| C. | Totally enclosed type |
| D. | Open type |
| Answer» B. Drip proof type | |
| 92. |
When an electric train is moving down a hill the DC motor operates as a DC |
| A. | Series motor |
| B. | Series generator |
| C. | Shunt motor |
| D. | Shunt generator |
| Answer» C. Shunt motor | |
| 93. |
method of starting a three phase induction motor needs six terminals. |
| A. | Stardelta |
| B. | Resistance starting |
| C. | Auto-transformer |
| D. | None of the above |
| Answer» B. Resistance starting | |
| 94. |
Which of the following drives is suitable for mines where explosive gas exists ? |
| A. | Steam engine |
| B. | Diesel engine |
| C. | Battery locomotive |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 95. |
Which of the following drive can be used for derricks and winches ? |
| A. | DC motors with Ward Leonard control |
| B. | AC slip-ring motors with variable resistance |
| C. | Pole changing squirrel cage motors |
| D. | Any of the above. |
| Answer» E. | |
| 96. |
The characteristics of drive for crane hoisting and lowering are which of thefollowing ? |
| A. | Precise control |
| B. | Smooth movement |
| C. | Fast speed control |
| D. | All of the above |
| Answer» E. | |
| 97. |
In series motor which of the following methods can be used for changing the flux per pole ? |
| A. | Tapped field control |
| B. | Diverter field control |
| C. | Series-parallel control |
| D. | Any of the above |
| Answer» E. | |
| 98. |
In case of speed control by injecting e.m.f. in the rotor circuit is possible, |
| A. | d.c. shunt motor |
| B. | schrage motor |
| C. | synchronous motor |
| D. | slip ring induction motor |
| Answer» E. | |
| 99. |
The motor normally used for crane travel is |
| A. | AC slip ring motor |
| B. | Ward Leonard controlled DC shunt motor |
| C. | Synchronous motor |
| D. | DC differentially compound motor. |
| Answer» B. Ward Leonard controlled DC shunt motor | |
| 100. |
The consideration involved in the selection of the type of electric drive for a particular application depends on |
| A. | Speed control range and its nature |
| B. | Starting torque |
| C. | Environmental conditions |
| D. | All of the above. |
| Answer» E. | |