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.
| 101. |
is not a part of ball bearing ? |
| A. | Inner race |
| B. | Outer race |
| C. | Cage |
| D. | Bush |
| Answer» E. | |
| 102. |
Besides a constant speed a synchronous rotor possesses which of the followingadvantages ? |
| A. | Lower cost |
| B. | Better efficiency |
| C. | High power factor |
| D. | All of the above |
| Answer» D. All of the above | |
| 103. |
For crane travel which off the following motors is normally used? |
| A. | Synchronous motor |
| B. | DC differential compound motor |
| C. | Ward Leonard controlled DC shunt motor |
| D. | AC slip ring motor |
| Answer» E. | |
| 104. |
Passive torques always oppose the motion of the driven machine. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» B. False | |
| 105. |
The load cycle for a motor driving a power press will be ......... |
| A. | Variable load |
| B. | Continuous |
| C. | Continuous but periodical |
| D. | Intermittent and variable load |
| Answer» E. | |
| 106. |
The output power of the centrifugal pump is proportional to the _________ of the speed. |
| A. | Square |
| B. | Cube |
| C. | Square-root |
| D. | Cube-root |
| Answer» C. Square-root | |
| 107. |
Which of the following motors are best for the rolling mills ? |
| A. | Single phase motors |
| B. | Squirrel cage induction motors |
| C. | Slip ring induction motors |
| D. | D.C. motors |
| Answer» E. | |
| 108. |
Introduction of automation in production process has become possible onlybecause of the use of |
| A. | An electric drive |
| B. | Group drives |
| C. | Individual and multi motor drives |
| D. | Individual Drive |
| Answer» D. Individual Drive | |
| 109. |
Calculate the useful power developed by a motor using the given data: P = 3000 W,I = 60 A, R = .4 Ω. Assume frictional losses are 200 W and windage losses are 400 W. |
| A. | 970 W |
| B. | 960 W |
| C. | 980 W |
| D. | 990 W |
| Answer» C. 980 W | |
| 110. |
Speed controlled by variation of field flux results in |
| A. | Constant power Drive |
| B. | Variable power Drive |
| C. | Constant torture Drive |
| D. | Variable torque Drive |
| Answer» B. Variable power Drive | |
| 111. |
The most suitable servo-motor application is __________ |
| A. | AC series motor |
| B. | DC series motor |
| C. | AC two-phase induction motor |
| D. | DC shunt motor |
| Answer» E. | |
| 112. |
......... is preferred for automatic drives |
| A. | Synchronous motors |
| B. | Word Leonard controlled DC motors |
| C. | None of the above |
| D. | Any of the above |
| Answer» E. | |
| 113. |
While selecting an electric motor for a floor mill, which electrical characteristics willbe of least significance ? |
| A. | Running characteristic |
| B. | Starting characteristics |
| C. | Efficiency |
| D. | Braking |
| Answer» E. | |
| 114. |
The pair used for frequency converter is |
| A. | Squirrel cage induction motor and synchronous motor |
| B. | Sleep ring induction motor and a synchronous motor |
| C. | Sleep ring induction motor and squirrel cage induction motor |
| D. | All of the above |
| Answer» B. Sleep ring induction motor and a synchronous motor | |
| 115. |
The number of sets used in pole changing type squirrel cage motors for derricks and winches, is |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 6. |
| Answer» C. 4 | |
| 116. |
A reluctance motor........ |
| A. | Is provided with slip rings |
| B. | Requires starting gear |
| C. | Has high cost |
| D. | Is compact |
| Answer» E. | |
| 117. |
There are four types of Water pumps. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» C. none | |
| 118. |
The cooling time constant is usually |
| A. | equal to the heating time constant |
| B. | more than heating time constant |
| C. | none of these. |
| D. | all |
| Answer» C. none of these. | |
| 119. |
A solar cell converts light energy into __________ |
| A. | Electrical energy |
| B. | Thermal energy |
| C. | Sound energy |
| D. | Heat energy |
| Answer» B. Thermal energy | |
| 120. |
Power factor in case of reluctance motor is |
| A. | nearly unity |
| B. | always leading |
| C. | 0.8 |
| D. | 0.3 to 0.4. |
| Answer» E. | |
| 121. |
While selecting motor for an air conditioner which of the following characteristicsis of great importance ? |
| A. | Type of bearings |
| B. | Type of enclosure |
| C. | Noise |
| D. | Arrangement for power transmis¬sion |
| Answer» D. Arrangement for power transmis¬sion | |
| 122. |
The conduction loss versus device current characteristic of a power MOSFET isbest approximated by a ________ |
| A. | Straight line |
| B. | Rectangular hyperbola |
| C. | Parabola |
| D. | Exponential decaying functions |
| Answer» D. Exponential decaying functions | |
| 123. |
Which of the following machines has heavy fluctuation of load ? |
| A. | Printing machine |
| B. | Punching machine |
| C. | Planer |
| D. | Lathe |
| Answer» C. Planer | |
| 124. |
A pole changing type squirrel cage motor used in derricks has four, eight andtwenty four poles. In this the lowest speed is used for |
| A. | lifting |
| B. | hoisting |
| C. | lowering |
| D. | landing the load. |
| Answer» E. | |
| 125. |
For handing fragile articles in a crane |
| A. | low speed is preferred |
| B. | medium speed is preferred |
| C. | high speed is preferr |
| Answer» B. medium speed is preferred | |
| 126. |
A typical active load is |
| A. | Hoist |
| B. | Lathe |
| C. | Blower |
| D. | Pump |
| Answer» B. Lathe | |
| 127. |
The selection of an electric motor for any application depends on which of thefollowing factors ? |
| A. | Electrical characteristics |
| B. | Mechanical characteristics |
| C. | Size and rating of motors |
| D. | All of the above |
| Answer» E. | |
| 128. |
........has least range of speed control |
| A. | Slip ring induction motor |
| B. | Synchronous motor |
| C. | DC shunt motor |
| D. | Schrage motor |
| Answer» C. DC shunt motor | |
| 129. |
Stator voltage control for speed control of induction motors is suitable for |
| A. | fan and pump drives |
| B. | drive of a crane |
| C. | running it as generator |
| D. | constant load drive. |
| Answer» B. drive of a crane | |
| 130. |
The basic elements of an electric drive are |
| A. | Electric motor and the transmission system |
| B. | Electric motor, the transmission and control system |
| C. | The transmission and control system |
| D. | Electric motor and conversion equipment |
| Answer» C. The transmission and control system | |
| 131. |
Fan type of loads exhibits which type of load torque characteristics? |
| A. | Constant torque characteristics |
| B. | Linearly rising torque characteristics |
| C. | Non-Linearly rising torque characteristics |
| D. | Non-Linearly decreasing torque characteristics |
| Answer» D. Non-Linearly decreasing torque characteristics | |
| 132. |
need frequent starting and stopping of electric motors, |
| A. | Paper mills |
| B. | Grinding mills |
| C. | Air-conditioners |
| D. | Lifts and hoists |
| Answer» E. | |
| 133. |
The unit of angular velocity is rad/s . |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» C. none | |
| 134. |
has the least value of starting torque to full load torque ratio. |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Squirrel cage induction motor |
| D. | Slip ring induction motor |
| Answer» D. Slip ring induction motor | |
| 135. |
Which of the following device is NOT suitable for parallel operation? |
| A. | MOSFET |
| B. | BJT |
| C. | IGBT |
| D. | TRIAC |
| Answer» C. IGBT | |
| 136. |
Specific energy consumption is affected by which of the following factors ? |
| A. | Retardation and acceleration values |
| B. | Gradient |
| C. | Distance between stops |
| D. | All of the above |
| Answer» E. | |
| 137. |
In squirrel cage induction motors which of the following methods of starting cannot be used ? |
| A. | Resistance in rotor circuit |
| B. | Resistance in stator circuit |
| C. | Auto-transformer starting |
| D. | Star-delta starting |
| Answer» B. Resistance in stator circuit | |
| 138. |
In case belt conveyors |
| A. | squirrel cage motors with direct-on-line starters are used |
| B. | single phase induction motors are used |
| C. | dc shunt motors are used |
| D. | induction motors with star-delta starters are used. |
| Answer» B. single phase induction motors are used | |
| 139. |
A motor of less than full load power rating can be used if the load is |
| A. | continuous duty |
| B. | short time duty |
| C. | intermittent periodic duty |
| D. | none of these. |
| Answer» C. intermittent periodic duty | |
| 140. |
When was the first solar cell invented? |
| A. | 1950 |
| B. | 1954 |
| C. | 1965 |
| D. | 1952 |
| Answer» C. 1965 | |
| 141. |
Boost converter is used to _________ |
| A. | Step down the voltage |
| B. | Step up the voltage |
| C. | Equalize the voltage |
| D. | Step up and step down the voltage |
| Answer» C. Equalize the voltage | |
| 142. |
Rotor resistance speed control is used in |
| A. | squirrel cage induction motor |
| B. | synchronous motor |
| C. | slip ring induction motor |
| D. | dc shunt motor. |
| Answer» D. dc shunt motor. | |
| 143. |
Torque inversely varies with the speed in the windage load torque component. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» C. none | |
| 144. |
Ward-Leonard controlled dc drives are generally used for |
| A. | light duty excavators |
| B. | medium duty excavators |
| C. | heavy duty excavators |
| D. | all of the above. |
| Answer» D. all of the above. | |
| 145. |
Which of the following is the disadvantage of electric traction over other systems oftraction ? |
| A. | Corrosion problems in the under-ground pipe work |
| B. | Short time power failure interrupts traffic for hours |
| C. | High capital outlay in fixed instal-lations beside route limitation |
| D. | Interference with communication lines |
| Answer» D. Interference with communication lines | |
| 146. |
In a centrifugal pump if the liquid to be pumped has density twice that of water, then the horse power required(as compared to that while pumping water) will be |
| A. | half |
| B. | same |
| C. | double |
| D. | four times. |
| Answer» D. four times. | |
| 147. |
Sleeve bearings |
| A. | Are normally of bronze |
| B. | Have self lubricating properties |
| C. | Are used where noise is to be avoided |
| D. | All of the above |
| Answer» E. | |
| 148. |
Load torque of the crane is independent of _________ |
| A. | Speed |
| B. | Seebeck eect |
| C. | Hall eect |
| D. | Thomson eect |
| Answer» B. Seebeck eect | |
| 149. |
What is the relationship between torque and speed in constant type loads? |
| A. | Torque is independent of speed |
| B. | Torque linearly increases with increase in speed |
| C. | Torque non-linearly increases with an increase in speed |
| D. | Torque non-linearly decreases with an increase in speed |
| Answer» B. Torque linearly increases with increase in speed | |
| 150. |
Which of the following motors are pre-ferred for overhead travelling cranes ? |
| A. | Slow speed motor |
| B. | Continuous duty motors |
| C. | Short time rated motors |
| D. | None of the above |
| Answer» D. None of the above | |