MCQOPTIONS
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MCQOPTIONS
This section includes 165 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
_ If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as$? |
| A. | Humming |
| B. | Hunting |
| C. | Crawling |
| D. | Cogging |
| Answer» D. Cogging | |
| 102. |
_ In case the air gap in an induction motor is increased$? |
| A. | The magnetizing current of the rotor will decrease |
| B. | The power factor will decrease |
| C. | Speed of motor will increase |
| D. | The windage losses will increase |
| Answer» C. Speed of motor will increase | |
| 103. |
_ In case of the induction motors the torque is$? |
| A. | Inversely proportional to (V-slip) |
| B. | Directly proportional to (slip)2 |
| C. | Inversely proportional to slip |
| D. | Directly proportional to slip |
| Answer» E. | |
| 104. |
_ Lubricant used for ball bearing is usually$? |
| A. | Graphite |
| B. | Grease |
| C. | Mineral oil |
| D. | Molasses |
| Answer» C. Mineral oil | |
| 105. |
_ Blocked rotor test on induction motors is used to find out$? |
| A. | Leakage reactance |
| B. | Power factor on short circuit |
| C. | Short-circuit current under rated voltage |
| D. | All of the above |
| Answer» E. | |
| 106. |
_ The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type$? |
| A. | Star connected only |
| B. | Delta connected only |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» D. None of the above | |
| 107. |
_ The starting torque of a 3 phase squirrel cage induction motor is$? |
| A. | Twice the full load torque |
| B. | 1.5 times the full load torque |
| C. | Equal to full load torque |
| D. | Any of the above |
| Answer» C. Equal to full load torque | |
| 108. |
_ The torque of a rotor in an induction motor under running condition is maximum$? |
| A. | At the unit value of slip |
| B. | At the zero value of slip |
| C. | At the value of the slip which makes rotor reactance per phase equal to the resistance per phase |
| D. | At the value of the slip which makes the rotor reactance half of the rotor |
| Answer» D. At the value of the slip which makes the rotor reactance half of the rotor | |
| 109. |
_ In three-phase squirrel-cage induction motors$? |
| A. | Rotor conductor ends are short-circuited through slip rings |
| B. | Rotor conductors are short-circuited through end rings |
| C. | Rotor conductors are kept open |
| D. | Rotor conductors are connected to insulation |
| Answer» C. Rotor conductors are kept open | |
| 110. |
_ The shaft of an induction motor is made of$? |
| A. | High speed steel |
| B. | Stainless steel |
| C. | Carbon steel |
| D. | Cast iron |
| Answer» D. Cast iron | |
| 111. |
_ Size of a high speed motor as compared to low speed motor for the same H.P. will be$? |
| A. | Bigger |
| B. | Smaller |
| C. | Same |
| D. | Any of the above |
| Answer» C. Same | |
| 112. |
__Less maintenance troubles are experienced in case of__ |
| A. | Slip ring induction motor |
| B. | Squirrel cage induction motor |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» C. Both (A) and (B) | |
| 113. |
_The starting torque of a three phase induction motor can be increased by$? |
| A. | Increasing slip |
| B. | Increasing current |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» D. None of the above | |
| 114. |
_Which type of bearing is provided in small induction motors to support the rotor shaft?$? |
| A. | Ball bearings |
| B. | Cast iron bearings |
| C. | Bush bearings |
| D. | None of the above |
| Answer» B. Cast iron bearings | |
| 115. |
If any two phases for an induction motor are interchanged$? |
| A. | The motor will run in reverse direction |
| B. | The motor will run at reduced speed |
| C. | The motor will not run |
| D. | The motor will burn |
| Answer» B. The motor will run at reduced speed | |
| 116. |
In induction motor, percentage slip depends on$? |
| A. | Supply frequency |
| B. | Supply voltage |
| C. | Copper losses in motor |
| D. | None of the above |
| Answer» D. None of the above | |
| 117. |
In an induction motor the relationship between stator slots and rotor slots is that$? |
| A. | Stator slots are equal to rotor slots |
| B. | Stator slots are exact multiple of rotor slots |
| C. | Stator slots are not exact multiple of rotor slots |
| D. | None of the above |
| Answer» D. None of the above | |
| 118. |
A change of 4% of supply voltage to an induction motor will produce a change of approximately$? |
| A. | 4% in the rotor torque |
| B. | 8% in the rotor torque |
| C. | 12% in the rotor torque |
| D. | 16% in the rotor torque |
| Answer» E. | |
| 119. |
The crawling in the induction motor is caused by$? |
| A. | Low voltage supply |
| B. | High loads |
| C. | Harmonics developed in the motor |
| D. | Improper design of the machine |
| Answer» D. Improper design of the machine | |
| 120. |
Temperature of the stator winding of a three phase induction motor is obtained by$? |
| A. | Resistance rise method |
| B. | Thermometer method |
| C. | Embedded temperature method |
| D. | All above methods |
| Answer» E. | |
| 121. |
If a 3-phase supply is given to the stator and rotor is short circuited rotor will move$? |
| A. | In the opposite direction as the direction of the rotating field |
| B. | In the same direction as the direction of the field |
| C. | In any direction depending upon phase sequence of supply |
| D. | None of these |
| Answer» C. In any direction depending upon phase sequence of supply | |
| 122. |
In medium sized induction motors, the slip is generally around$? |
| A. | 0.04 % |
| B. | 0.4 % |
| C. | 4 % |
| D. | 14 % |
| Answer» D. 14 % | |
| 123. |
The shape of the torque/slip curve of induction motor is$? |
| A. | Parabola |
| B. | Hyperbola |
| C. | Rectangular parabola |
| D. | Straight line |
| Answer» D. Straight line | |
| 124. |
Step-less speed control of induction motor is possible by which of the following methods?$? |
| A. | e.m.f. injection in rotor eueuit |
| B. | Changing the number of poles |
| C. | Cascade operation |
| D. | None of the above |
| Answer» C. Cascade operation | |
| 125. |
Short-circuit test on an induction motor cannot be used to determine$? |
| A. | Windage losses |
| B. | Copper losses |
| C. | Transformation ratio |
| D. | Power scale of circle diagram |
| Answer» B. Copper losses | |
| 126. |
Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor?$? |
| A. | By changing the number of stator poles |
| B. | Rotor rheostat control |
| C. | By operating two motors in cascade |
| D. | By injecting e.m.f. in the rotor circuit |
| Answer» B. Rotor rheostat control | |
| 127. |
The maximum torque in an induction motor depends on$? |
| A. | Frequency |
| B. | Rotor inductive reactance |
| C. | Square of supply voltage |
| D. | All of the above |
| Answer» E. | |
| 128. |
In a squirrel cage motor the induced e.m.f. is$? |
| A. | Dependent on the shaft loading |
| B. | Dependent on the number of slots |
| C. | Slip times the stand still e.m.f. induced in the rotor |
| D. | None of the above |
| Answer» D. None of the above | |
| 129. |
An induction motor with 1000 r.p.m. speed will have$? |
| A. | 8 poles |
| B. | 6 poles |
| C. | 4 poles |
| D. | 2 poles |
| Answer» C. 4 poles | |
| 130. |
An induction motor with 1000 r.p.m. speed will have? |
| A. | 8 poles |
| B. | 6 poles |
| C. | 4 poles |
| D. | 2 poles |
| Answer» C. 4 poles | |
| 131. |
Slip rings are usually made of |
| A. | Copper |
| B. | Carbon |
| C. | Phosphor bronze |
| D. | Aluminium |
| Answer» D. Aluminium | |
| 132. |
In a three-phase induction motor, the number of poles in the rotor winding is always |
| A. | Zero |
| B. | More than the number of poles in stator |
| C. | Less than number of poles in stator |
| D. | Equal to number of poles in stator |
| Answer» E. | |
| 133. |
The rotor of an induction motor runs at |
| A. | Synchronous speed |
| B. | Below synchronous speed |
| C. | Above synchronous speed |
| D. | Any of the above |
| Answer» C. Above synchronous speed | |
| 134. |
The injected e.m.f. in the rotor of induction motor must have |
| A. | Zero frequency |
| B. | The same frequency as the slip frequency |
| C. | The same phase as the rotor e.m.f. |
| D. | High value for the satisfactory speed control |
| Answer» C. The same phase as the rotor e.m.f. | |
| 135. |
DOL starting of induction motors is usually restricted to |
| A. | Low horsepower motors |
| B. | Variable speed motors |
| C. | High horsepower motors |
| D. | High speed motors |
| Answer» B. Variable speed motors | |
| 136. |
Star-delta starting of motors is not possible in case of |
| A. | Single phase motors |
| B. | Variable speed motors |
| C. | Low horse power motors |
| D. | High speed motors |
| Answer» B. Variable speed motors | |
| 137. |
Slip ring motor is preferred over squirrel cage induction motor where |
| A. | High starting torque is required |
| B. | Load torque is heavy |
| C. | Heavy pull out torque is required |
| D. | All of the above |
| Answer» B. Load torque is heavy | |
| 138. |
The 'crawling' in an induction motor is caused by |
| A. | High loads |
| B. | Low voltage supply |
| C. | Improper design of machine |
| D. | Harmonics developed in the motor |
| Answer» E. | |
| 139. |
In the squirrel-cage induction motor the rotor slots are usually given slight skew |
| A. | To reduce the magnetic hum and locking tendency of the rotor |
| B. | To increase the tensile strength of the rotor bars |
| C. | To ensure easy fabrication |
| D. | None of the above |
| Answer» B. To increase the tensile strength of the rotor bars | |
| 140. |
Slip ring motor is recommended where |
| A. | Speed control is required |
| B. | Frequent starting, stopping and reversing is required |
| C. | High starting torque is needed |
| D. | All above features are required |
| Answer» E. | |
| 141. |
The term 'cogging' is associated with |
| A. | Three-phase transformers |
| B. | Compound generators |
| C. | D.C. series motors |
| D. | Induction motors |
| Answer» E. | |
| 142. |
In a star-delta starter of an induction motor |
| A. | Resistance is inserted in the stator |
| B. | Reduced voltage is applied to the stator |
| C. | Resistance is inserted in the rotor |
| D. | Applied voltage per stator phase is 57.7% of the line voltage |
| Answer» E. | |
| 143. |
The speed characteristics of an induction motor closely resemble the speed-load characteristics of which of the following machines |
| A. | D.C. series motor |
| B. | D.C. shunt motor |
| C. | Universal motor |
| D. | None of the above |
| Answer» C. Universal motor | |
| 144. |
The circle diagram for an induction motor cannot be used to determine |
| A. | Efficiency |
| B. | Power factor |
| C. | Frequency |
| D. | Output |
| Answer» B. Power factor | |
| 145. |
It is advisable to avoid line starting of induction motor and use starter because |
| A. | It will run in reverse direction |
| B. | It will pick up very high speed and may go out of step |
| C. | Motor takes five to seven times its full load current |
| D. | Starting torque is very high |
| Answer» D. Starting torque is very high | |
| 146. |
Insertion of reactance in the rotor circuit |
| A. | Reduces starting torque as well as maximum torque |
| B. | Increases starting torque as well as maximum torque |
| C. | Increases starting torque but maximum torque remains unchanged |
| D. | Increases starting torque but maximum torque decreases |
| Answer» B. Increases starting torque as well as maximum torque | |
| 147. |
In the circle diagram for induction motor, the diameter of the circle represents |
| A. | Slip |
| B. | Rotor current |
| C. | Running torque |
| D. | Line voltage |
| Answer» C. Running torque | |
| 148. |
The complete circle diagram of induction motor can be drawn with the help of data found from |
| A. | No-load test |
| B. | Blocked rotor test |
| C. | Stator resistance test |
| D. | All of the above |
| Answer» E. | |
| 149. |
Which is of the following data is required to draw the circle diagram for an induction motor? |
| A. | Block rotor test only |
| B. | No load test only |
| C. | Block rotor test and no-load test |
| D. | Block rotor test, no-load test and stator resistance test |
| Answer» E. | |
| 150. |
The power scale of circle diagram of an induction motor can be found from |
| A. | Stator resistance test |
| B. | No-load test only |
| C. | Short-circuit test only |
| D. | None of the above |
| Answer» D. None of the above | |