MCQ on single phase motor 81-100

81. 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

82. 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✔

83. The speed of a universal motor is generally reduced by using
(a) gear trains✔
(b) V-belts
(c) brakes
(d) chains

84. 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✔

85. 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

86. 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

87. 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

88. Which motor is normally free from mechanical and magnetic vibrations ?
(a) Split phase motor
(b) Universal motor
(c) Hysteresis motor✔
(d) Shaded pole motor

89. 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

90. A reluctance motor
(a) is self-starting
(b) is constant speed motor
(c) needs no D.C. excitation
(d) all of the above✔

91. In a hysteresis motor, the rotor must have
(a) retentivity✔
(b) resistivity
(c) susceptibility
(d) none of the above

92. The rotor of a hysteresis motor is made of
(a) aluminium
(b) cast iron
(c) chrome steel✔
(d) copper

93. The electric motor used in portable drills is
(a) capacitor run motor
(b) hysteresis motor
(c) universal motor✔
(d) repulsion motor

94. 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

95. 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

96. Torque developed by a single phase induction motor at starting is
(a) pulsating
(b) uniform
(c) none of the above
(d) nil✔

97. 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

98. 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

99. 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

100. 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