ELECTRICAL ENGINEERING SINGLE PHAGE MOTOR MOSTLY ASKED MCQ PDF

1.In capacitor start single-phase
motors
  1. current in the starting winding leads the voltage
  2. current in the starting winding lags the voltage
  3. current in the starting winding is in phase with voltage
    in running winding
  4. none of the above
ANSWER : current in the starting
winding leads the voltage
2.If the capacitor of a single-phase
motor is short-circuited
  1. the motor will not start
  2. the motor will run
  3. the motor will run in reverse direction
  4. the motor will run in the same direction at reduced
    r.p.m.
ANSWER : : the motor will not start
3.Which of the following motors is
used in mixies ?
  1. Repulsion motor
  2. Reluctance motor
  3. Hysteresis motor
  4. Universal motor
ANSWER : : Universal motor
4.The value of starting capacitor of
a fractional horse power motor will be
  1. 100 uF
  2. 00 uF
  3. 300 uF
  4. 400 uF
  5. ANSWER : 300 uF
5.If a particular application needs
high speed and high starting torque, then which of the following motor will be
preferred ?
  1. Universal motor
  2. Shaded pole type motor
  3. Capacitor start motor
  4. Capacitor start and run motor
ANSWER : : Universal motor
6.In repulsion motor direction of
rotation of motor
  1. is opposite to that of brush shift
  2. is the same as that of brush shift
  3. is independent of brush shift
  4. none
ANSWER : is the same as that of brush shift
7.Which of the following motor will
have relatively higher power factor ?
  1. Capacitor run motor
  2. Shaded pole motor
  3. Capacitor start motor
  4. Split phase motor
ANSWER : : Capacitor run motor
8.Burning out of windings is due to
  1. short circuited capacitor
  2. capacitor value hiving changed
  3. open circuiting of capacitor
  4. none of the above
ANSWER : : short circuited capacitor
9.The range of efficiency for shaded
pole motors is
  1. 95% to 99%
  2. 80% to 90%
  3. 50% to 75%
  4. 5% to 35%
ANSWER : : 5% to 35%
10.A capacitor-start single phase
induction motor is switched on to supply with its capacitor replaced by an inductor
of equivalent reactant value. It will
  1. start and then stop
  2. start and run slowly
  3. start and run at rated speed
  4. not start at all
ANSWER : : not start at all
11.In a capacitor start and run
motors the function of the running capacitor in series with the auxiliary winding
is to
  1. improve power factor
  2. increase overload capacity
  3. reduce fluctuations in torque
  4. to improve torque
ANSWER : : improve power factor
12.In a shaded pole single-phase
motor, the revolving field is produced by the use of
  1. inductor
  2. capacitor
  3. resistor
  4. shading coils
ANSWER : : shading coils
13.Direction of rotation of a split
phase motor can be reversed by reversing the connection of
  1. running winding only
  2. starting winding only
  3. either (1) or (2)
  4. both (1) and (2)
ANSWER : : either (1) or (2)
14.The direction of rotation of an
hysteresis motor is determined by
  1. interchanging the supply leads
  2. position of shaded pole with respect to main pole
  3. retentivity of the rotor material
  4. none of these
ANSWER : : position of shaded pole
with respect to main pole
15.In a split phase motor
  1. the starting winding is connected through a centrifugal
    switch
  2. the running winding is connected through a centrifugal
    switch
  3. both starting and running windings are connected
    through a centrifugal switch
  4. centrifugal switch is used to control supply voltage
ANSWER : : the starting winding is
connected through a centrifugal switch
16.The rotor torque developed by a
single-phase motor at starting is
  1. more than the rated torque
  2. rated torque
  3. less than the rated torque
  4. zero
ANSWER : : zero
17.Which of the following motor will
give relatively high starting torque ?
  1. Capacitor start motor
  2. Capacitor run motor
  3. Split phase motor
  4. Shaded pole motor
ANSWER : : Capacitor start motor
18.Which of the following motors is
inherently self starting ?
  1. Split motor
  2. Shaded-pole motor
  3. Reluctance motor
  4. None of these
ANSWER : : Shaded-pole motor
19.Short-circuited is used in
  1. repulsion induction motor
  2. repulsion motor
  3. repulsion start induction run motor
  4. none of the above
ANSWER : : repulsion start induction
run motor 
20.The power factor of a
single-phase induction motor is usually
  1. lagging
  2. always leading
  3. unity
  4. unity to 0.8 leading
ANSWER : : lagging
21.In a shaded pole motor, the
shading coil usually consist of
  1. a single turn of heavy wire which is in parallel with
    running winding
  2. a single turn of heavy copper wire which is
    short-circuited and carries only induced current
  3. a multilayer fine gauge copper wire in parallel with
    running winding
  4. none of the above
ANSWER : : a single turn of heavy
copper wire which is short-circuited and carries only induced current
22.The running winding of a single
phase motor on testing with meggar is found to be ground. Most probable location of the ground will be
  1. at the end connections
  2. at the end terminals
  3. anywhere on the winding inside a slot
  4. at the slot edge where coil enters or comes out of the
    slot
ANSWER : : at the slot edge where
coil enters or comes out of the slot
23.A centrifugal switch is used to
disconnect starting winding when motor has
  1. run for about 1 minute
  2. run for about 5 minutes
  3. picked up about 50 to 70 per cent of rated speed
  4. picked up about 10 to 25 per cent of rated speed
ANSWER : : picked up about 50 to 70
per cent of rated speed
24.In a capacitor start motor, the
phase displacement between starting and running winding can be nearly
  1. 10
  2. 30
  3. 60
  4. 90
ANSWER : : 90
25.In a capacitor start single-phase
motor, when capacitor is replaced by a resistance
  1. torque will increase
  2. the motor will consume less power
  3. motor will run in reverse direction
  4. motor will continue to run in same direction
ANSWER : : motor will continue to
run in same direction
26.Which of the following motors can
be run on AC. as well as D.C. supply ?
  1. Universal motor
  2. Repulsion motor
  3. Synchronous motor
  4. Reluctance motor
ANSWER : : Universal motor
27.Which of the following motors
will operate at high power factor ?
  1. Shaped pole motor
  2. Split phase motor
  3. Capacitor start motor
  4. Capacitor run motor
ANSWER : : Capacitor run motor
28..In split-phase motor auxiliary
winding is of
  1. thick wire placed at the bottom of the slots
  2. thick wire placed at the top of the slots
  3. thin wire placed at the top of the slots
  4. thin wire placed at the bottom of the slots
ANSWER : : thin wire placed at the
top of the slots
29.In case of high speed universal
motor which of the following needs more attention ?
  1. End play
  2. Air gap
  3. Insulation in rotor
  4. Balancing of rotor
ANSWER : : Balancing of rotor
30.In case of a shaded pole motor
the direction of rotation of the motor is
  1. from main pole to shaded pole
  2. from shaded pole to main pole
  3. either of the above depending on voltage
  4. either of the above depending on power factor
ANSWER : : from main pole to shaded
pole
31.In A.C. series motor compensating
winding is employed to
  1. reduce the effects of armature reaction
  2. increase the torque
  3. reduce sparking at the brushes
  4. none of the above
ANSWER : : reduce sparking at the
brushes
32.In a two value capacitor motor,
the capacitor used for running purposes is
  1. air capacitor
  2. paper spaced oil filled type
  3. ceramic type
  4. a.c. electrolytic type
ANSWER : : paper spaced oil filled
type
33.Which type of load is offered by
cranes and hoists ?
  1. Gradually varying load
  2. Non-reversing, no-load start
  3. Reversing, light start
  4. Reversing, heavy start
ANSWER : Reversing, heavy start
34.Which of the following motors has
highest starting torque ?
  1. Repulsion motor
  2. Shaped pole motor
  3. Capacitor-start motor
  4. Split-phase motor
ANSWER : : Capacitor-start motor
35.Which of the following
single-phase motors has relatively poor starting torque ?
  1. Universal motor
  2. Repulsion motor
  3. Capacitor motor
  4. All single phase motors have zero starting torque
ANSWER : : Capacitor motor
36.The wattage of motor for driving
domestic sewing machine will be around
  1. 100 to 150 W
  2. 40 to 75 W
  3. 10 to 30 W
  4. 5 to 10 W
ANSWER : : 100 to 150 W
37.Single phase induction motor
usually operates on
  1. 0.6 power factor lagging
  2. 0.8 power factor lagging
  3. 0.8 power factor leading
  4. unity power factor
ANSWER : : 0.6 power factor lagging
38.The motor used on small lathes is
usually
  1. universal motor
  2. D.C. shunt motor
  3. single-phase capacitor run motor
  4. 3-phase synchronous motor
ANSWER : : single-phase capacitor
run motor
39.Which of the following motors can
be used for unity power factor ?
  1. Capacitor run motor
  2. Shaded pole motor
  3. Hysteresis motor
  4. Schrage motor
ANSWER : : Schrage motor
40.A hysteresis motor works on the
principle of
  1. hysteresis loss
  2. magnetization of rotor
  3. eddy current loss
  4. electromagnetic induction
ANSWER : : hysteresis loss
41.The speed of a universal motor is
generally reduced by using
  1. gear trains
  2. V-belts
  3. brakes
  4. chains
ANSWER : : gear trains
42.The repulsion-start induction-run
motor is used because of
  1. good power factor
  2. high efficiency
  3. minimum cost
  4. high starting torque
ANSWER : : high starting
torque 
43.Which of the following motors is
preferred for tape-recorders ?
  1. Shaded pole motor
  2. Hysteresis motor
  3. Two value capacitor motor
  4. Universal motor
ANSWER : : Hysteresis motor
44.The wattage rating for a ceiling
fan motor will be in the range
  1. 200 to 250 W
  2. 250 to 500 W
  3. 50 to 150 W
  4. 10 to 20 W
ANSWER : : 50 to 150 W
45.Which of the following
single-phase induction motors is generally used in time phonographs ?
  1. Resistance start
  2. Capacitor start capacitor run
  3. Shaded pole
  4. Universal
ANSWER : Shaded pole
46.A schrage motor can run on
  1. zero slip
  2. negative slip
  3. positive slip
  4. all of the above
ANSWER : : all of the above
47.Which of the following
single-phase motors is suitable for timing and control purposes ?
  1. Reluctance motor
  2. Series motor
  3. Repulsion motor
  4. Universal motor
ANSWER : : Reluctance motor
48.Which of the following motor will
give the highest starting torque ?
  1. D.C. shunt motor
  2. Schrage motor
  3. Repulsion start and induction run motor
  4. Universal motor
ANSWER : : Schrage motor
49.A universal motor can run on
  1. A.C. only
  2. D.C. only
  3. either A.C. or D.C.
  4. none of the above
ANSWER : : either A.C. or D.C.
50.A single-phase induction motor is
  1. inherently self-starting with high torque
  2. inherently self-starting with low torque
  3. inherently non-self-starting with low torque
  4. inherently non-self-starting with high torque
ANSWER : : inherently
non-self-starting with low torque
51.For which of the applications a
reluctance motor is preferred ?
  1. Electric shavers
  2. Refrigerators
  3. Signalling and timing devices
  4. Lifts and hoists
ANSWER : : Signalling and timing
devices
52.Torque developed by a single
phase induction motor at starting is
  1. pulsating
  2. uniform
  3. none of the above
  4. nil
ANSWER : : nil
53.As hysteresis motors are free
from mechanical and magnetic vibrations therefore these are considered as suitable
for
  1. fans
  2. blowers
  3. sound equipment
  4. mixer grinders
ANSWER : : sound equipment
54.In which single-phase motor, the
rotor has no teeth or winding ?
  1. Split phase motor
  2. Reluctance motor
  3. Hysteresis motor
  4. Universal motor
ANSWER : : Hysteresis motor
55.The rotor of a hysteresis motor
is made of
  1. aluminum
  2. cast iron
  3. chrome steel
  4. copper
ANSWER : : chrome steel
56.The speed control of universal
motor used for sewing machines is by
  1. friction
  2. varying the resistance
  3. tapping the field
  4. centrifugal mechanism
ANSWER : : varying the resistance
57.In repulsion motor, maximum
torque is developed when
  1. brush axis is at 45 electrical to the field axis
  2. brush axis coincides with the field axis
  3. brush axis is at 90 electrical to the field axis
  4. none of the above
ANSWER : : brush axis is at 45
electrical to the field axis
58.In a hysteresis motor, the rotor
must have
  1. retentivity
  2. resistivity
  3. susceptibility
  4. none of the above
ANSWER : : retentivity
59.The motor used for the
compressors is
  1. d.c. series motor
  2. shaded pole motor
  3. capacitor-start capacitor-run motor
  4. reluctance motor
ANSWER : : capacitor-start
capacitor-run motor
60.The direction of rotation of
universal motor can be reversed the by reversing the flow of current through
  1. armature winding
  2. field winding
  3. either armature winding or field winding
  4. none of the above
ANSWER : : either armature winding
or field winding
61.A reluctance motor
  1. is self-starting
  2. is constant speed motor
  3. needs no D.C. excitation
  4. all of the above
ANSWER : : all of the above
62.Which of the following motors is
used for unity power factor ?
  1. Hysteresis motor
  2. Schrage motor
  3. Universal motor
  4. Reluctance motor
ANSWER : : Schrage motor
63.The speed/load characteristics of
a universal motor is same as that of
  1. A.C. motor
  2. D.C. shunt motor
  3. D.C. series motor
  4. none of the above
ANSWER : : D.C. series motor
64.In a ceiling fan employing
capacitor run motor
  1. secondary winding surrounds the primary winding
  2. primary winding surrounds the secondary winding
  3. both are usual arrangements
  4. none of the above
ANSWER : : secondary winding
surrounds the primary winding
65.Which motor is normally free from
mechanical and magnetic vibrations ?
  1. Split phase motor
  2. Universal motor
  3. Hysteresis motor
  4. Shaded pole motor
ANSWER : : Hysteresis motor
66.Speed torque characteristic of a
repulsion induction motor is similar to that of a D.C.
  1. shunt motor
  2. series motor
  3. compound motor
  4. separately excited motor
ANSWER : : compound motor
67.The shaded pole motor is used for
  1. high starting torque
  2. low starting torque
  3. medium starting torque
  4. very high starting torque
ANSWER : : low starting torque
68.Which of the following motors is
used in a situation where load increases with speed ?
  1. Induction motor
  2. Three-phase series motor
  3. Schrage motor
  4. Hysteresis motor
ANSWER : : Three-phase series motor
69.In repulsion motor, zero torque
is developed when
  1. brush axis is 45 electrical to field axis
  2. brush axis coincides with the field axis
  3. brush axis is 90 electrical to field axis
  4. both (2) and (3)
ANSWER : : both (2) and (3)
70.In split phase motor main winding
is of
  1. thin wire placed at the top of the slots
  2. thin wire placed at the bottom of the slots
  3. thick wire placed at the bottom of the slots
  4. thick wire placed at the top of the” slots
ANSWER : : thick wire placed at the
bottom of the slots
71.The electric motor used in
portable drills is
  1. capacitor run motor
  2. hysteresis motor
  3. universal motor
  4. repulsion motor
ANSWER : : universal motor
72.The purpose of stator winding in
the compensated repulsion motor is to
  1. provide mechanical balance
  2. improve power factor and provide better speed
    regulation
  3. prevent hunting in the motor
  4. eliminate armature reaction
ANSWER : : improve power factor and
provide better speed regulation
73.The rotor slots, in an induction
motor, are usually not quite parallel to the shaft because it
  1. improves the efficiency
  2. helps the rotor teeth to remain under the stator teeth
  3. helps in reducing the tendency of the rotor teeth to
    remain under the stator teeth
  4. improves the power factor
ANSWER : : helps in reducing the
tendency of the rotor teeth to remain under the stator teeth
74.If the centrifugal switch does
not open at 70 to 80 percent of synchronous speed of motor, it would result in
  1. damage to the starting winding
  2. damage to the centrifugal switch
  3. overloading of running winding
  4. none of the above
ANSWER : : damage to the starting
winding
75.Which of the following
applications always have some load whenever switched on ?
  1. Vacuum cleaners
  2. Fan motors
  3. Pistol drills
  4. All of the above
ANSWER : : Pistol drills
76.Most of the fractional horsepower
motors have either
  1. hard and annealed bearings
  2. ball or roller bearings
  3. soft and porous bearings
  4. plain or sleeve bearings
ANSWER : : plain or sleeve bearings
77.After the starting winding of a
single phase induction motor is disconnected from supply, it continues to run only on
  1. running winding
  2. rotor winding
  3. field winding
  4. compensating winding
ANSWER : : running winding
78.In a universal motor, the most
common cause of brush sparking is
  1. open armature winding
  2. shorted armature winding
  3. shorted field winding”
  4. high commutator mica
ANSWER : : all of the above
79.Speed control of a universal
motor is achieved by
  1. varying field flux with tapped field windings
  2. connecting rheostat in series
  3. applying variable voltage by means of silicon
    controlled rectifier
  4. applying variable voltage by means of variable
    auto-transformer
ANSWER : : all of the above methods
90.A universal motor is one which
  1. can be operated either on D.C. or A.C. supply at
    approximately the same speed and output
  2. can be marketed internationally
  3. runs at dangerously high speed on no-load
  4. runs at dangerously high speed on load
ANSWER : can be operated either on D.C. or A.C. supply at
approximately the same speed and output
91.To reverse the direction of
rotation of a capacitor start motor while it is running we should 
  1. Disconnect motor from the supply till it stops then
    reconnect it to supply with reversed
    connection of main or auxiliary winding
  2. Disconnect motor from supply and immediately reconnect
    it to supply with reversed
    connections of the main winding
  3. Reverse the direction of connection of the auxiliary
    winding and after motor comes to rest then connect auxiliary winding to
    the supply
  4. Reverse the direction of connections of the auxiliary
    winding and immediately connect it to supply
ANSWER : : Disconnect motor from the
supply till it stops then reconnect it to supply with reversed connection of
main or auxiliary winding
92.Which of the following motors is
used in tape-recorders ?
  1. Hysteresis motor
  2. Reluctance motor
  3. Capacitor-run motor
  4. Universal motor
ANSWER : : Hysteresis motor
93.A shaded pole motor does not
possess
  1. centrifugal switch
  2. capacitor
  3. commutator
  4. all of the above
ANSWER : : all of the above
94.Which of the following motors has
two separate windings on the motor ?
  1. Repulsion motor
  2. Repulsion induction motor
  3. Repulsion start induction run motor
  4. None of the above
ANSWER : : Repulsion induction motor
95.In a A.C. series motor armature
coils are usually connected to commutator
  1. through resistance
  2. through reactances
  3. through capacitors
  4. solidly
ANSWER : : through resistance
96.If starting winding of a
single-phase induction motor is left in the circuit, it will
  1. run faster
  2. spark at light loads
  3. draw excessive current and overheat
  4. run slower
ANSWER : : draw excessive current
and overheat
97.Which of the following statements
regarding reluctance-start motor is incorrect ?
  1. It is similar to reluctance motor
  2. It is basically an induction motor and not a
    synchronous one
  3. So far as its basic working principle is concerned, it
    is similar to shaded pole motor
  4. the air-gap between rotor and salient poles is non-
    uniform
ANSWER : : It is similar to
reluctance motor
98.Which of the following statements
regarding two value capacitor motor is incorrect ?
  1. It is a reversing motor
  2. It is preferred to permanent-split single-value
    capacitor motor where frequent reversals are required
  3. It has low starting as well as rushing currents
  4. It has high starting torque
ANSWER : : It is preferred to
permanent-split single-value capacitor motor where frequent reversals are required
99.Which of the following statements
regarding repulsion-start induction motor is incorrect ?
  1. It requires more maintenance of commutator and other
    mechanical devices
  2. It makes quite a bit of noise on starting
  3. In fractional horse power motors, it has replaced the
    capacitor motors
  4. It is not easily reversed
ANSWER : : In fractional horse power
motors, it has replaced the capacitor motors
100.A.C. series motor as compared to
D.C. series motor has
  1. smaller brush width
  2. less number of field turns
  3. more number of armature turns
  4. less air gap
ANSWER : : all of the above
101.Which of the following
statements regarding a reluctance motor is incorrect ?
  1. It cannot be reversed, ordinarily
  2. It requires no D.C. field excitation for its operation
  3. It is nothing else but a single-phase, salient pole
    synchronous-induction motor
  4. Its squirrel cage-rotor is of unsymmetrical magnetic
    construction in order to vary reluctance path between stator and rotor
ANSWER : : It cannot be reversed,
ordinarily
102.If the centrifugal switch of a
two-value capacitor motor using two capacitors fails to open then
  1. motor will not come upto speed
  2. motor will not carry the load
  3. current drawn by the motor will be excessively high
  4. electrolytic capacitor will, in all probability, suffer
    break down
ANSWER : : electrolytic capacitor
will, in all probability, suffer break down
103.If a D.C. series motor is
operated on A.C. supply, it will
  1. spark excessively
  2. have poor efficiency
  3. have poor power factor
  4. all of the above
ANSWER : : all of the above
104.Locked rotor current of a shaded
pole motor is
  1. equal to full load current
  2. less than full load current
  3. slightly more than full load current
  4. several times the full load current
ANSWER : : slightly more than full
load current
105.In case of a reluctance motor,
when the load is increased so that it cannot maintain synchronous speed the
motor will
  1. become unstable
  2. draw excessive armature current and may burn out
  3. fall out of synchronism and come to stand still
  4. run as induction motor
ANSWER : : run as induction motor
106.Two-value capacitor motor finds
increased application as compressor motor in small home air conditioners
because
  1. it is comparatively cheaper
  2. it has almost non-destructible capacitor
  3. it has low starting as well as running currents at
    relatively high power factor
  4. it is quiet in operation
ANSWER : : it has low starting as
well as running currents at relatively high power factor
107.If a single phase induction
motor runs slower than normal, the most likely defect is
  1. worn bearings
  2. short-circuit in the winding
  3. open-circuit in the winding
  4. none of the above
ANSWER : : worn bearings
108.Starting winding of a single
phase motor of a refrigerator is disconnected from the circuit by means of a
  1. magnetic relay
  2. thermal relay
  3. centrifugal switch
  4. none of the above
ANSWER : : magnetic relay
109.The capacitors used in
single-phase capacitor motors have no
  1. voltage rating
  2. dielectric medium
  3. polarity marking
  4. definite value
ANSWER : : polarity marking
110.The speed of a universal motor is
usually reduced by using
  1. gearing
  2. belts
  3. brakes
  4. chains
ANSWER : : gearing
111.The starting winding of a
single-phase motor is placed in
  1. armature
  2. field
  3. rotor
  4. stator
ANSWER : : stator
112.Which of the following
statements regarding hysteresis motor is in incorrect ?
  1. It is extremely sensitive to fluctuations in supply
    voltage
  2. Its high starting torque is due to its high rotor
    hysteresis loss
  3. It is extremely quiet in operation
  4. It accelerates from rest to full-speed almost
    instantaneously
ANSWER : : It is extremely sensitive
to fluctuations in supply voltage
113. Which of the following
statements regarding single-phase induction motors correct ?
  1. It requires only one winding
  2. It can rotate in one direction only
  3. It is self-starting
  4. It is not self-starting
ANSWER : : It is not self-starting
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