ELECTRICIAN
(THEORY)
SEMESTER-III
JULY 2018
Which of the following is not a part of theAlternator's specification plate ?
(a) Voltage
(b) Phase
(c)KVA
(d) Type of winding
Answer: (d) Type of winding
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A single phase Hysteresis motor can run at.......
(a) Synchronous speed only
(b) Sub synchronous speed only
(c) Synchronous and super synchronous speed
(d) Synchronous and sub synchronous speed
Answer: (a) Synchronous speed only
The direction of rotation of Hysteresis motor
is reversed by............
(a) Reversing supply leads
(b) Shift shaded pole with respect to main pole
(c) Both (a) & (b)
(d) None of these
Answer: (b) Shift shaded pole with respect to main pole
The motor used in domestic mixer grinder is................
(a) DC motor
(b) Induction motor
(c) Universal motor
(d) Synchronous motor
Answer: (c) Universal motor
A Stepper motor is a.....
(a) DC motor
(b) Two phase motor
(c) Single phase motor
(d) Multi phase motor
Answer:
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The slip ring induction motors have..............rotor.
(a) Phase wound
(b) Squirrel cage
(c) Squirrel cage with winding
(d) Diamond coil wound
Answer: (a) Phase wound
The difference between the speed of a rotating
magnetic field and the associated rotor is called .............
(a) Split
(b) Salient pole
(c) Slip
(d) Pul1 out tor(lue •
Answer: (c) Slip
If the voltage is reduced to half, the torque
developed by an induction motor will be
reduced to..................
(a) 1/4 of original torque
(b) 1/2 of original torque
(c) 1/8 of original torque
(d) 2/3 of original torque
Answer:
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In a three phase induction motor, the cage bars
of the rotor are arranged in an offset
pattern to the axis of rotation in order to prevent ...............
(a) Torque fluctuation
(b) Over heating
(c) Speed variation
(d) Voltage drop on load
Answer: (a) Torque fluctuation
The variation of power factor with respect to the field
current is called ...............
(a) V curve
(b) Inverted curve
(c) Hysteresis curve
(d) Circle diagram
Answer: (b) Inverted curve
When asynchronous motor is running at
synchronous speed, the damper winding
produces.................
(a) Damping torque
(b) Eddy current torque
(c) Torque aiding the developed torque
(d) No torque
Answer: (d) No torque
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A motor which can conveniently be operated
at lagging as well as leading power factor is
the...................
(a) Squirrel cage induction motor
(b) Wound rotor induction motor
(c) Synchronous motor
(d) DC shunt motor
Answer: (c) Synchronous motor
A synchronous motor is operating on no load
at unity power factor. If the field current is
increased, power factor will become............
(a) Leading and current will decrease
(b) Leading and current will increase
(c) Lagging and current will decrease
(d) Lagging and current will increase
Answer: (a) Leading and current will decrease
The frequency of ripple in the output voltage of a
three phase Half controlled bridge rectifier
depends on the................
(a) Firing angle
(b) Load inductance
(c) Load resistance
(d) Supply frequency
Answer: (d) Supply frequency
A PWM switching scheme is used in a three phase inverter to........
(a) Reduce total harmonic distortion with modest filtering
(b) Reduce low order harmonics and increase high order harmonics
(c) Minimize the load on DC side
(d) Increase the life of the batteries
Answer: (b) Reduce low order harmonics and increase
high order harmonics
Which of the following is a Shell type of transformer lamination?
(a) T & I type
(b) E & T type
(c) U & I type
(d) T & U type
Answer: (d) T & U type
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For a given number of poles(2) and armature conductors,
a hp winding will carry.............a wave winding.
(a) More current than
(b) Same current as
(c) Less current than
(d) Half the current than
Answer: (a) More current than
An Eight pole duplex lap winding will have ......... parallel paths.
(a) 8
(b) 12
(c) 32
(d) 16
Answer: (d) 16
In a simplex wave winding the number of
parallel paths is equal to
(a) Number of poles in the machine
(b) Two
(c) Number of pair poles
(d) One
Answer: (b) Two
The number of parallel paths in simplex lap
winding is equal to...
(a) Two
(b) Number of poles
(c) Number of pair poles
(d) One
Answer: (c) Number of pair poles
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In a lap winding, the number of brushes required
is equal to............
(a) Number of coils
(b) Number of pairs of poles
(c) Number of poles
(d) Commutator pitch
Answer: (c) Number of poles
In a wave winding, the commutator pitch is
approximately equal to..................
(a) Twice the pole pitch
(b) Thrice the pole pitch
(c) Half the pole pitch
(d) Pole pitch
Answer: (a) Twice the pole pitch
The AC armature winding of an alternator
operates at........the field winding.
(a) The same voltage as
(b) Much higher voltage than
(c) Much less voltage than
(d) Half the voltage than
Answer: (b) Much higher voltage than
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The stator of an alternator is wound for..........on the stator.
(a) A more number of poles than
(b) Less number of poles than
(c) The same number of poles as
(d) Twice the number of poles
Answer: (c) The same number of poles as
The Damper windings are used in the alternators to ……
(a) Reduce eddy current loss
(b) Achieve synchronism
(c) Reduce winding losses
(d) Prevent hunting
Answer: (d) Prevent hunting
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The AC armature winding of an alternator is.................
(a) Always star connected .
(b) Star delta connected
(c) Generally delta connected
(d) Pi connected
Answer: (a) Always star connected
While testing a Fluorescent tube starter with series
testing board, the starter is considered good if the lamp................
(a) Glows continuously
(b) Does not glow at all
(c) Continuously flickers
(d) Glows initially then turns off permanently
Answer: (c) Continuously flickers
The illurnination power of a lighting source is measured in.
(a) Lumen
(b) Candela
(c) Foot candle
(d) Candle power
Answer: (d) Candle power
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As per IE rules, the lighting load in a sub-circuit
of the house wiring should not be than.........watts.
(a) 1500W
(b) 1200W
(c) 1000W
(d) 800W
Answer: (d) 800W
As per IE rules, the load in a power sub-circuit in
house wiring is normally restricted to........watt
and number of outlets to.........
(a) 5000, two
(b) 3000, two
(c) 4000, three
(d) 4500, four
Answer: (b) 3000, two
In a Fluorescent tube fixture, if the tube does
not strike a glow but both filaments glow
red, the possible defect is............
(a) Opened choke coil
(b) Short circuited choke coil
(c) Starter contacts permanently opened
(d) Starter contacts permanently shorted
Answer: (d) Starter contacts permanently shorted
The electrical wiring in factories and industries
is done by.........,.
(a) Cleats
(b) Casing capping
(c) Surface metal conduit
(d) Surface PVC conduit
Answer: (c) Surface metal conduit
The magnetic operating limit of C-type of
MCB’s is..........times of the rated current.
(a) 5 to 10
(b) 20 to 30
(c) 3 to 5
(d) 10 to 20
Answer: (a) 5 to 10
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Which one of the following lamps has the
longest operating life?
(a) LED lamp
(b) Fluorescent tube light
(c) CFL
(d) Incandescent lamp
Answer: (a) LED lamp
When the Growler is connected with 230 V,
AC supply and armature is placed over it,
the arrangement behaves like a....................
(a) Potential Divider
(b) AC Motor
(c) Transformer .
(d) DC Bridge
Answer: (c) Transformer
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A motor normally fitted to a domestic
vacuum cleaner is.............motor.
(a) Universal
(b) Cage Induction
(c) Wound rotor
(d) Shunt Wound
Answer: (a) Universal
The type of single-phase induction motor
having the highest power factor at full load
is....:..............
(a) Shaded pole type
(b) Split-phase type
(c) Capacitor-start type
(d) Capacitor-run type
Answer: (d) Capacitor-run type
The method of braking an induction motor by
interchanging the supply to two of the
stator phase windings is called..................
(a) Plugging
(b) Stopping
(c) Commutation
(d) Retarding
Answer: (a) Plugging
If a three phase induction motor is switched on with
one phase disconnected, the motor will ................
(a) Run at low speed
(b) Burn Out
(c) Run at High Speed
(d) Not Run
Answer: (b) Burn Out
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The running of induction motors at slow and
steady speed much less than the actual
speed is known as.
(a) Crawling
(b) Damping,
(c) Sinking
(d) Ageing
Answer: (a) Crawling
The distribution of load between two alternators
operating in parallel can be changed by
changing...............
(a) Phase sequence .
(b) Field excitation of alternators
(c) Current direction
(d) Driving torques of prime movers
Answer: (d) Driving torques of prime movers
A 3-phase synchronous motor connected to
AC mains is running at full load and unity
power factor. If its shaft load is reduced by half,
with field current held constant, its new
power factor will be.........
(a) Unity
(b) Leading
(c) Lagging
(d) Dependent upon motor parameters
Answer: (b) Leading
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The starting torque of slip-ring induction motor
can be increased by inserting a suitable ……..
in series with the rotor circuit of the motor,
(a) Capacitor
(b) Resistance
(c) Inductor
(d) Overload relay
Answer: (b) Resistance
The Growler instrument is made in ...............
type of iron core.
(a) E & I
(b) Shell
(c) T&U
(d) H
Answer: (d) H
The voltage regulation of an alternator with power
factor of 0.8 lagging is ……. at unity power factor.
(a) Greater than
(b) The same as
(c) Smaller than
(d) 100%
Answer: (a) Greater than
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A ceiling fan uses.......
(a) Capacitor start motor
(b) Universal motor
(c) Capacitor start and capacitor run motor
(d) Split-phase motor
Answer: (a) Capacitor start motor
The voltage regulation of an alternator is larger
than that of a DC generator because of ..................
(a) Large armature resistance
(b) Large leakage reactance
(c) Complex effects of armature reaction
(d) Small armature resistance
Answer: (c) Complex effects of armature reaction
[f the excitation an alternator operating in
parallel with other alternators, is increased
above the normal value of excitation, its .........
(a) Output current decreases
(b) Power factor becomes more lagging
(c) Power factor becomes more leading
(d) Output KW decreases
Answer: (b) Power factor becomes more lagging
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