McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 51. |
Which of the following single-phase motors has relatively poor starting torque ? |
| A. | Universal motor |
| B. | Repulsion motor |
| C. | Capacitor motor |
| D. | All single phase motors have zero starting torque |
| Answer» C. Capacitor motor | |
| 52. |
Which type of load is offered by cranes and hoists ? |
| A. | Gradually varying load |
| B. | Non-reversing, no-load start |
| C. | Reversing, light start |
| D. | Reversing, heavy start |
| Answer» D. Reversing, heavy start | |
| 53. |
The speed of a universal motor is generally reduced by using |
| A. | gear trains |
| B. | V-belts |
| C. | brakes |
| D. | chains |
| Answer» A. gear trains | |
| 54. |
Which of the following motors can be used for unity power factor ? |
| A. | Capacitor run motor |
| B. | Shaded pole motor |
| C. | Hysteresis motor |
| D. | Schrage motor |
| Answer» D. Schrage motor | |
| 55. |
When a D.C. series motor is connected to A.C. supply, the power factor will be low because of |
| A. | high inductance of field and armature circuits |
| B. | induced current in rotor due to variations of flux |
| C. | fine copper wire winding |
| D. | none of the above |
| Answer» A. high inductance of field and armature circuits | |
| 56. |
The direction of rotation of universal motor can be reversed the by reversing the flow of current through |
| A. | armature winding |
| B. | field winding |
| C. | either armature winding or field winding |
| D. | none of the above |
| Answer» C. either armature winding or field winding | |
| 57. |
In which single-phase motor, the rotor has no teeth or winding ? |
| A. | Split phase motor |
| B. | Reluctance motor |
| C. | Hysteresis motor |
| D. | Universal motor |
| Answer» C. Hysteresis motor | |
| 58. |
Which motor is normally free from mechanical and magnetic vibrations ? |
| A. | Split phase motor |
| B. | Universal motor |
| C. | Hysteresis motor |
| D. | Shaded pole motor |
| Answer» C. Hysteresis motor | |
| 59. |
As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for |
| A. | fans |
| B. | blowers |
| C. | sound equipment |
| D. | mixer grinders |
| Answer» C. sound equipment | |
| 60. |
A reluctance motor |
| A. | is self-starting |
| B. | is constant speed motor |
| C. | needs no D.C. excitation |
| D. | all of the above |
| Answer» D. all of the above | |
| 61. |
In a hysteresis motor, the rotor must have |
| A. | retentivity |
| B. | resistivity |
| C. | susceptibility |
| D. | none of the above |
| Answer» A. retentivity | |
| 62. |
The rotor of a hysteresis motor is made of |
| A. | aluminium |
| B. | cast iron |
| C. | chrome steel |
| D. | copper |
| Answer» C. chrome steel | |
| 63. |
The electric motor used in portable drills is |
| A. | capacitor run motor |
| B. | hysteresis motor |
| C. | universal motor |
| D. | repulsion motor |
| Answer» C. universal motor | |
| 64. |
Which of the following applications always have some load whenever switched on ? |
| A. | Vacuum cleaners |
| B. | Fan motors |
| C. | Pistol drills |
| D. | All of the above |
| Answer» C. Pistol drills | |
| 65. |
The speed control of universal motor used for sewing machines is by |
| A. | friction |
| B. | varying the resistance |
| C. | tapping the field |
| D. | centrifugal mechanism |
| Answer» B. varying the resistance | |
| 66. |
Torque developed by a single phase induction motor at starting is |
| A. | pulsating |
| B. | uniform |
| C. | none of the above |
| D. | nil |
| Answer» D. nil | |
| 67. |
In split phase motor main winding is of |
| A. | thin wire placed at the top of the slots |
| B. | thin wire placed at the bottom of the slots |
| C. | thick wire placed at the bottom of the slots |
| D. | thick wire placed at the top of the" slots |
| Answer» C. thick wire placed at the bottom of the slots | |
| 68. |
In repulsion motor, maximum torque is developed when |
| A. | brush axis is at 45° electrical to the field axis |
| B. | brush axis coincides with the field axis |
| C. | brush axis is at 90° electrical to the field axis |
| D. | none of the above |
| Answer» A. brush axis is at 45° electrical to the field axis | |
| 69. |
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in |
| A. | damage to the starting winding |
| B. | damage to the centrifugal switch |
| C. | overloading of running winding |
| D. | none of the above |
| Answer» A. damage to the starting winding | |
| 70. |
Speed torque characteristic of a repulsion induction motor is similar to that of a D.C. |
| A. | shunt motor |
| B. | series motor |
| C. | compound motor |
| D. | separately excited motor |
| Answer» C. compound motor | |
| 71. |
In a ceilingfan employing capacitor run motor |
| A. | secondary winding surrounds the primary winding |
| B. | primary winding surrounds the secondary winding |
| C. | both are usual arrangements |
| D. | none of the above |
| Answer» A. secondary winding surrounds the primary winding | |
| 72. |
The shaded pole motor is used for |
| A. | high starting torque |
| B. | low starting torque |
| C. | medium starting torque |
| D. | very high starting torque |
| Answer» B. low starting torque | |
| 73. |
The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it |
| A. | improves the efficiency |
| B. | helps the rotor teeth to remain under the stator teeth |
| C. | helps in reducing the tendency of the rotor teeth to remain under the stator teeth |
| D. | improves the power factor |
| Answer» C. helps in reducing the tendency of the rotor teeth to remain under the stator teeth | |
| 74. |
The speed/load characteristics of a universal motor is same as that of |
| A. | A.C. motor |
| B. | D.C. shunt motor |
| C. | D.C. series motor |
| D. | none of the above |
| Answer» C. D.C. series motor | |
| 75. |
The purpose of stator winding in the compensated repulsion motor is to |
| A. | provide mechanical balance |
| B. | improve power factor and provide better speed regulation |
| C. | prevent hunting in the motor |
| D. | eliminate armature reaction |
| Answer» B. improve power factor and provide better speed regulation | |
| 76. |
Which of the following motors is used for unity power factor ? |
| A. | Hysteresis motor |
| B. | Schrage motor |
| C. | Universal motor |
| D. | Reluctance motor |
| Answer» B. Schrage motor | |
| 77. |
The motor used for the compressors is |
| A. | d.c. series motor |
| B. | shaded pole motor |
| C. | capacitor-start capacitor-run motor |
| D. | reluctance motor |
| Answer» C. capacitor-start capacitor-run motor | |
| 78. |
Which of the following motors is used in a situation where load increases with speed ? |
| A. | Induction motor |
| B. | Three-phase series motor |
| C. | Schrage motor |
| D. | Hysteresis motor |
| Answer» B. Three-phase series motor | |
| 79. |
In repulsion motor, zero torque is developed when |
| A. | brush axis is 45° electrical to field axis |
| B. | brush axis coincides with the field axis |
| C. | brush axis is 90° electrical to field axis |
| D. | both (b) and (c) |
| Answer» D. both (b) and (c) | |
| 80. |
Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed |
| A. | 30 to 40 |
| B. | 70 to 80 |
| C. | 80 to 90 |
| D. | 100 |
| Answer» B. 70 to 80 | |
| 81. |
Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a |
| A. | magnetic relay |
| B. | thermal relay |
| C. | centrifugal switch |
| D. | none of the above |
| Answer» A. magnetic relay | |
| 82. |
If a single phase induction motor runs slower than normal, the most likely defect is |
| A. | worn bearings |
| B. | short-circuit in the winding |
| C. | open-circuit in the winding |
| D. | none of the above |
| Answer» A. worn bearings | |
| 83. |
Which of the following motors is used in tape-recorders ? |
| A. | Hysteresis motor |
| B. | Reluctance motor |
| C. | Capacitor-run motor |
| D. | Universal motor |
| Answer» A. Hysteresis motor | |
| 84. |
Which of the following statements regarding two value capacitor motor is incorrect ? |
| A. | It is a reversing motor |
| B. | It is preferred to permanent-split single-value capacitor motor where frequent reversals are required |
| C. | It has low starting as well as rush¬ing currents |
| D. | It has high starting torque |
| Answer» B. It is preferred to permanent-split single-value capacitor motor where frequent reversals are required | |
| 85. |
Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because |
| A. | it is comparatively cheaper |
| B. | it has almost non-destructible capacitor |
| C. | it has low starting as well as running currents at relatively high power factor |
| D. | it is quiet in operation |
| Answer» C. it has low starting as well as running currents at relatively high power factor | |
| 86. |
If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then |
| A. | motor will not come upto speed |
| B. | motor will not carry the load |
| C. | current drawn by the motor will be excessively high |
| D. | electrolytic capacitor will, in all probability, suffer break down |
| Answer» D. electrolytic capacitor will, in all probability, suffer break down | |
| 87. |
In a universal motor, the most common cause of brush sparking is |
| A. | open armature winding |
| B. | shorted armature winding |
| C. | shorted field winding" |
| D. | all of the above |
| Answer» D. all of the above | |
| 88. |
If starting winding of a single-phase induction motor is left in the circuit, it will |
| A. | run faster |
| B. | spark at light loads |
| C. | draw excessive current and overheat |
| D. | run slower |
| Answer» C. draw excessive current and overheat | |
| 89. |
Most of the fractional horsepower motors have either |
| A. | hard and annealed bearings |
| B. | ball or roller bearings |
| C. | soft and porous bearings |
| D. | plain or sleeve bearings |
| Answer» D. plain or sleeve bearings | |
| 90. |
Which of the following statements regarding reluctance-start motor is incorrect ? |
| A. | It is similar to reluctance motor |
| B. | It is basically an induction motor and not a synchronous one |
| C. | So far as its basic working principle is concerned, it is similar to shaded pole motor |
| D. | the air-gap between rotor and salient poles is non- uniform |
| Answer» A. It is similar to reluctance motor | |
| 91. |
To reverse the direction of rotation of acapacitor start motor while it is running we should |
| A. | disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding |
| B. | disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding |
| C. | reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply |
| D. | reverse the direction of connections of the auxiliary winding and im-mediately connect it to supply |
| Answer» A. disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding | |
| 92. |
In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will |
| A. | become unstable |
| B. | draw excessive armature current and may burn out |
| C. | fall out of synchronism and come to stand still |
| D. | run as induction motor |
| Answer» D. run as induction motor | |
| 93. |
Which of the following motors has two separate windings on the motor ? |
| A. | Repulsion motor |
| B. | Repulsion induction motor |
| C. | Repulsion start induction run motor |
| D. | None of the above |
| Answer» B. Repulsion induction motor | |
| 94. |
A shaded pole motor does not possess |
| A. | centrifugal switch |
| B. | capacitor |
| C. | commutator |
| D. | all of the above |
| Answer» D. all of the above | |
| 95. |
In a A.C. series motor armature coils are usually connected to commutator |
| A. | through resistance |
| B. | through reactances |
| C. | through capacitors |
| D. | solidly |
| Answer» A. through resistance | |
| 96. |
Which of the following statements regarding a reluctance motor is incorrect ? |
| A. | It cannot be reversed, ordinarily |
| B. | It requires no D.C. field excitation for its operation |
| C. | It is nothing else but a single-phase, salient pole synchronous-induction motor |
| D. | Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path bet¬ween stator and rotor |
| Answer» A. It cannot be reversed, ordinarily | |
| 97. |
A universal motor is one which |
| A. | can be operated either on D.C. or A.C. supply at approximately the same speed and output |
| B. | can be marketed internationally |
| C. | runs at dangerously high speed on no-load |
| D. | none |
| Answer» A. can be operated either on D.C. or A.C. supply at approximately the same speed and output | |
| 98. |
A repulsion motor is equipped with |
| A. | slip rings |
| B. | commutator |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» B. commutator | |
| 99. |
The capacitors used in single-phase capacitor motors have no |
| A. | voltage rating |
| B. | dielectric medium |
| C. | polarity marking |
| D. | definite value |
| Answer» C. polarity marking | |
| 100. |
If a D.C. series motor is operated on A.C. supply, it will |
| A. | spark excessively |
| B. | have poor efficiency |
| C. | have poor power factor |
| D. | all of the above |
| Answer» D. all of the above | |
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