single phase induction motors MCQs – Page 2

Practise focused single phase induction motors questions with marked answers for exam preparation and subject revision.

single phase induction motors Mcqs
51. If a single phase induction motor runs slower than normal, the most likely defect is_____________?
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A. open-circuit in the winding

B. short-circuit in the winding

C. worn bearings

D. none of the above

52. Which of the following statements regarding single-phase induction motors correct?
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A. It is not self-starting

B. It can rotate in one direction only

C. It requires only one winding

D. It is self-starting

53. Burning out of winding is due to___________?
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A. capacitor value hiving changed

B. none of the above

C. open circuiting of capacitor

D. short circuited capacitor
54. Which motor is normally free from mechanical and magnetic vibrations ?
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A. Universal motor

B. Shaded pole motor

C. Hysteresis motor

D. Split phase motor

55. In a two value capacitor motor, the capacitor used for running purposes is_______________?
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A. a.c. electrolytic type

B. air capacitor

C. paper spaced oil filled type

D. ceramic type

56. In case of a shaded pole motor the direction of rotation of the motor is__________?
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A. from shaded pole to main pole

B. from main pole to shaded pole

C. either of the above depending on power factor

D. either of the above depending on voltage

57. The wattage rating for a ceiling fan motor will be in the range_________?
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A. 50 to 150 W

B. 250 to 500 W

C. 200 to 250 W

D. 10 to 20 W

58. Which of the following statements regarding a reluctance motor is incorrect ?
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A. Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path between stator and rotor

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. It cannot be reversed, ordinarily
59. The purpose of stator winding in the compensated repulsion motor is to_____________?
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A. improve power factor and provide better speed regulation

B. prevent hunting in the motor

C. eliminate armature reaction

D. provide mechanical balance

60. In a capacitor start motor, the phase displacement between starting and running winding can be nearly__________?
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A. 60

B. 30

C. 10

D. 90
61. Which of the following motor will have relatively higher power factor ?
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A. Capacitor run motor

B. Capacitor start motor

C. Split phase motor

D. Shaded pole motor

62. Most of the fractional horsepower motors have either___________?
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A. soft and porous bearings

B. hard and annealed bearings

C. plain or sleeve bearings

D. ball or roller bearings

63. Single phase induction motor usually operates on__________?
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A. 0.6 power factor lagging

B. unity power factor

C. 0.8 power factor lagging

D. 0.8 power factor leading

64. Which of the following motors has highest starting torque ?
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A. Split-phase motor

B. Capacitor-start motor

C. Shaped pole motor

D. Repulsion motor

65. Which of the following applications always have some load whenever switched on ?
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A. Vacuum cleaners

B. Fan motors

C. All of the above

D. Pistol drills
66. Which of the following statements regarding hysteresis motor is in incorrect?
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A. It accelerates from rest to full-speed almost instantaneously

B. It is extremely quiet in operation

C. It is extremely sensitive to fluctuations in supply voltage

D. Its high starting torque is due to its high rotor hysteresis loss

67. In capacitor start single-phase motors____________?
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A. current in the starting winding lags the voltage

B. current in the starting winding leads the voltage

C. none of the above

D. current in the starting winding is in phase with voltage in running winding

68. The speed control of universal motor used for sewing machines is by____________?
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A. friction

B. varying the resistance

C. tapping the field

D. centrifugal mechanism

69. The rotor of a hysteresis motor is made of___________?
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A. cast iron

B. aluminium

C. chrome steel

D. copper

70. Which of the following motors is inherently self starting ?
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A. None of these

B. Split motor

C. Shaded-pole motor

D. Reluctance motor

71. Which of the following motors has two separate windings on the motor ?
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A. None of the above

B. Repulsion start induction run motor

C. Repulsion motor

D. Repulsion induction motor
72. For which of the applications a reluctance motor is preferred ?
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A. Lifts and hoists

B. Electric shavers

C. Refrigerators

D. Signalling and timing devices
73. The shaded pole motor is used for__________?
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A. high starting torque

B. medium starting torque

C. low starting torque

D. very high starting torque

74. The starting winding of a single-phase motor is placed in_________?
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A. armature

B. field

C. rotor

D. stator
75. In a shaded pole single-phase motor, the revolving field is produced by the use of_________?
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A. inductor

B. resistor

C. shading coils

D. capacitor

76. If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in_________?
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A. none of the above

B. overloading of running winding

C. damage to the starting winding

D. damage to the centrifugal switch

77. A reluctance motor____________?
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A. all of the above

B. is self-starting

C. is constant speed motor

D. needs no D.C. excitation

78. A shaded pole motor does not possess___________?
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A. capacitor

B. commutator

C. all of the above

D. centrifugal switch

79. Which type of load is offered by cranes and hoists ?
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A. Reversing, light start

B. Non-reversing, no-load start

C. Reversing, heavy start

D. Gradually varying load

80. The wattage of motor for driving domestic sewing machine will be around__________?
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A. 5 to 10 W

B. 100 to 150 W

C. 10 to 30 W

D. 40 to 75 W

81. If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then____________?
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A. current drawn by the motor will be excessively high

B. electrolytic capacitor will, in all probability, suffer break down

C. motor will not come up to speed

D. motor will not carry the load

82. A capacitor-start single phase induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance value. It will______________?
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A. not start at all

B. start and run slowly

C. start and then stop

D. start and run at rated speed

83. A universal motor is one which______________?
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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

84. The speed of a universal motor is usually reduced by using____________?
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A. gearing

B. chains

C. belts

D. brakes

85. A hysteresis motor works on the principle of__________?
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A. electromagnetic induction

B. hysteresis loss

C. eddy current loss

D. magnetisation of rotor

86. In a shaded pole motor, the shading coil usually consist of___________?
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A. a single turn of heavy copper wire which is short-circuited and carries only induced current

B. a multilayer fine gauge copper wire in parallel with running winding

C. none of the above

D. a single turn of heavy wire which is in parallel with running winding

87. Which of the following motor will give relatively high starting torque ___________?
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A. Shaded pole motor

B. Capacitor run motor

C. Capacitor start motor

D. Split phase motor

88. A.C. series motor as compared to D.C. series motor has__________?
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A. all of the above

B. less air gap

C. less number of field turns

D. more number of armature turns

E. smaller brush width

89. Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because_____________?
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A. it has almost non-destructible capacitor

B. it has low starting as well as running currents at relatively high power factor

C. it is quiet in operation

D. it is comparatively cheaper

90. A shaded pole motor can be used for_____________?
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A. circulators

B. any of the above

C. toys

D. hair dryers

91. Which of the following motors is used for unity power factor ?
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A. Reluctance motor

B. Hysteresis motor

C. Schrage motor

D. Universal motor

92. The speed/load characteristics of a universal motor is same as that of_____________?
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A. none of the above

B. D.C. series motor

C. D.C. shunt motor

D. A.C. motor

93. In a ceilingfan employing capacitor run motor____________?
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A. secondary winding surrounds the primary winding

B. primary winding surrounds the secondary winding

C. both are usual arrangements

D. none of the above

94. Which of the following motors is used in tape-recorders ____________?
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A. Hysteresis motor

B. Reluctance motor

C. Universal motor

D. Capacitor-run motor

95. To reverse the direction of rotation of acapacitor start motor while it is running we should___________?
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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 connections of the auxiliary winding and immediately connect it to supply

D. reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply

96. If a particular application needs high speed and high starting torque, then which of the following motor will be preferred ?
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A. Shaded pole type motor

B. Capacitor start and run motor

C. Capacitor start motor

D. Universal motor
97. Which of the following single-phase motors has relatively poor starting torque ?
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A. Universal motor

B. All single phase motors have zero starting torque

C. Repulsion motor

D. Capacitor motor
98. Speed control of a universal motor is achieved by__________?
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A. all of the above methods

B. applying variable voltage by means of silicon controlled rectifier

C. applying variable voltage by means of variable auto-transformer

D. connecting rheostat in series

E. varying field flux with tapped field windings

99. Which of the following single-phase induction motors is generally used in time phonographs ?
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A. Resistance start

B. Capacitor start capacitor run

C. Shaded pole

D. Universal

100. In a A.C. series motor armature coils are usually connected to commutator____________?
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A. solidly

B. through capacitors

C. through reactances

D. through resistance