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