HIL Placement-Paper

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  1. 1. A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second.
    (a) 100 n
    (b) 50 jt
    (c) 25 jt
    (d) 5 n
    Ans: a

    2. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms.
    (a) 2.5
    (b) 5
    (c) 10
    (d) 15
    Ans: c


    3. The period of a wave is
    (a) the same as frequency
    (6) time required to complete one cycle
    (c) expressed in amperes
    (d) none of the above
    Ans: b


    4. The form factor is the ratio of
    (a) peak value to r.m.s. value
    (6) r.m.s. value to average value
    (c) average value to r.m.s. value
    (d) none of the above
    Ans: b


    5. The period of a sine wave is _____ seconds.
    Its frequency is
    (a) 20 Hz
    (b) 30 Hz
    (c) 40 Hz
    (d) 50 Hz
    Ans: d


    6. A heater is rated as 230 V, 10 kW, A.C. The value 230 V refers to
    (a) average voltage
    (b) r.m.s. voltage
    (c) peak voltage
    (d) none of the above
    Ans: b

    7. If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is
    (a) a sinusoid of the same frequency
    (b) a sinusoid of half the original frequency
    (c) a sinusoid of double the frequency
    (d) not a sinusoid
    Ans: a

    8. The peak value of a sine wave is 200 V. Its average value is
    (a) 127.4 V
    (b) 141.4 V
    (c) 282.8 V
    (d)200V
    Ans: a

    9. If two sine waves of the same frequency have a phase difference of JT radians, then
    (a) both will reach their minimum values at the same instant
    (b) both will reach their maximum values at the same instant
    (c) when one wave reaches its maximum value, the other will reach its minimum value
    (d) none of the above
    Ans: c

    10. The voltage of domestic supply is 220V. This figure represents
    (a) mean value
    (b) r.m.s. value
    (c) peak value
    (d) average value
    Ans: a

    11. Two waves of the same frequency have opposite phase when the phase angle between them is
    (a) 360°
    (b) 180°
    (c) 90°
    (d) 0°
    Ans: b

    12. The power consumed in a circuit element will be least when the phase difference between the current and
    voltage is
    (a) 180"
    (b) 90°
    (c) 60°
    (d) 0°
    Ans: b

    13. The r.m.s. value and mean value is the same in the case of
    (a) triangular wave
    (6) sine wave
    (c) square wave
    (d) half wave rectified sine wave
    Ans: c

    14. For the same peak value which of the following wave will 'have the highest r.m.s. value ?
    (a) square wave
    (b) half wave rectified sine wave
    (c) triangular wave
    (d) sine wave
    Ans: a

    15. For the same peak value, which of the following wave has the least mean value ?
    (a) half wave rectified sine wave
    (b) triangular wave
    (c) sine wave
    (d) square wave
    Ans: a

    16. For a sine wave with peak value Imax the r.m.s. value is
    (a) 0.5 Imax
    (b) 0.707
    (c) 0.9
    (d) 1.414 Lmax
    Ans: b

    17. Form Factor is the ratio of
    (a) average value/r.m.s. value
    (b) average value/peak value
    (e) r.m.s. value/average value
    (d) r.m.s. value/peak value
    Ans: c

    18. Form factor for a sine wave is
    (a) 1.414
    (b) 0.707
    (c) 1.11
    (d) 0.637
    Ans: c

    19. For a sine wave with peak value Emax______8.30. the average value is
    (a) 0.636 Emax
    (b) 0.707 Emax
    (c) 0.434 EWc
    (d) lAUEmax
    Ans: a

    20. For a frequency of 200 Hz, the time period will be
    (a) 0.05 s
    (b) 0.005 s
    (c) 0.0005 s
    (d) 0.5 s
    Ans: b

    21. The phase difference between voltage and current wave through a circuit element is given as 30°. The essential condition is that
    (a) both waves must have same frequency
    (b) both waves must have identical peak values
    (c) both waves must have zero value at the same time
    (d) none of the above
    Ans: a

    22. The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.
    (a) 90
    (b) 60
    (c) 45
    (d) 30
    Ans: c

    23. Capacitive reactance is more when
    (a) capacitance is less and frequency of supply is less
    (b) capacitance is less and frequency of supply is more
    (c) capacitance is more and frequency of supply is less
    (d) capacitance is more and frequency of supply is more
    Ans: a

    24. In a series resonant circuit, the impedance of the circuit is
    (a) minimum
    (b) maximum
    (c) zero
    (d) none of the above
    Ans: a

    25. Power factor of an electrical circuit is equal to
    (a) R/Z
    (b) cosine of phase angle difference between current and voltage
    (c) kW/kVA
    (d) ratio of useful current to total current Iw/I
    (e) all above
    Ans: e

    26. The best place to install a capacitor is
    (a) very near to inductive load
    (b) across the terminals of the inductive load
    (c) far away from the inductive load
    (d) any where
    Ans: b

    27. Poor power factor
    (a) reduces load handling capability of electrical system
    (b) results in more power losses in the electrical system
    (c) overloads alternators, transformers and distribution lines
    (d) results in more voltage drop in the line
    (e) results in all above
    Ans: e

    28. Capacitors for power factor correction are rated in
    (a) kW
    (b) kVA
    (c) kV
    (d) kVAR
    Ans: d

    29. In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its half value
    (a) will change the maximum value of current at resonance
    (6) will change the resonance frequency
    (c) will change the impedance at resonance frequency
    (d) will increase the selectivity of the circuit
    Ans: d

    30. Pure inductive circuit
    (a) consumes some power on average
    (b) does not take power at all from a line
    (c) takes power from the line during some part of the cycle and then returns back to it during other part of the cycle
    (d) none of the above
    Ans: c

    31. Inductance affects the direct current flow
    (a) only at the time of turning off
    (b) only at the time of turning on
    (c) at the time of turning on and off
    (d) at all the time of operation
    Ans: c

    32. Inductance of a coil Varies
    (a) directly as the cross-sectional area of magnetic core
    (b) directly as square of number of turns
    (c) directly as the permeability of the core
    (d) inversely as the length of the iron path
    (e) as (a) to (d)
    Ans: e

    33. All the rules and laws of D.C. circuit also apply to A.C. circuit containing
    (a) capacitance only
    (b) inductance only
    (c) resistance only
    (d) all above
    Ans: c

    34. Time constant of an inductive circuit
    (a) increases with increase of inductance and decrease of resistance
    (b) increases with the increase of inductance and the increase of resistance
    (c) increases with decrease of inductance and decrease of resistance
    (d) increases with decrease of inductance and increase of resistance
    Ans: a

    35. Power factor of an inductive circuit is usually improved by connecting capacitor to it in
    (a) parallel
    (b) series
    (c) either (a) or (b)
    (d) none of the above
    Ans: a

    36. In a highly capacitive circuit the
    (a) apparent power is equal to the actual power
    (b) reactive power is more than the apparent power
    (c) reactive power is more than the actual powetf
    (d) actual power is more than its reactive power
    Ans: c

    37. Power factor of the following circuit will be zero
    (a) resistance
    (b) inductance
    (c) capacitance
    (d) both (b) and (c)
    Ans: d

    38. Power factor of the following circuit will be unity
    (a) inductance
    (b) capacitance
    (c) resistance
    (d) both (a) and (b)
    Ans: c

    39. Power factor of the system is kept high
    (a) to reduce line losses
    (b) to maximise the utilization of the capacities of generators, lines and transformers
    (c) to reduce voltage regulation of the line
    (d) due to all above reasons
    Ans: d

    40. The time constant of the capacitance circuit is defined as the time during which voltage
    (a) falls to 36.8% of its final steady value
    (b) rises to 38.6% of its final steady value
    (c) rises to 63.2% of its final steady value
    (d) none of the above
    Ans: c

    41. In a loss-free R-L-C circuit the transient current is
    (a) oscillating
    (b) square wave
    (c) sinusoidal
    (d) non-oscillating
    Ans: c

    42. The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces
    (a) the more heat than produced by A.C. when flowing through the same circuit
    (b) the same heat as produced by A.C. when flowing through the same circuit
    (c) the less heat than produced by A.C. flowing through the same circuit
    (d) none of the above
    Ans: b

    43. The square waveform of current has following relation between r.m.s. value and average value.
    (a) r.m.s. value is equal to average value
    (b) r.m.s. value of current is greater than average value
    (c) r.m.s. value of current is less than average value
    (d) none of the above
    Ans: a

    44. The double energy transient occur in the
    (a) purely inductive circuit
    (b) R-L circuit
    (c) R-C circuit
    (d) R-L-C circuit
    Ans: d

    45. The transient currents are associated with the
    (a) changes in the stored energy in the inductors and capacitors
    (b) impedance of the circuit
    (c) applied voltage to the circuit
    (d) resistance of the circuit
    Ans: a

    46. The power factor at resonance in R-L- C parallel circuit is
    (a) zero
    (b) 0.08 lagging
    (c) 0.8 leading
    (d) unity
    Ans: d

    47. In the case of an unsymmetrical alternating current the average value must always be taken over
    (a) unsymmetrical part of the wave form
    (b) the quarter cycle
    (c) the half cycle
    (d) the whole cycle
    Ans: d

    48. In a pure resistive circuit
    (a) current lags behind the voltage by 90°
    (b) current leads the voltage by 90°
    (c) current can lead or lag the voltage by 90°
    (d) current is in phase with the voltage
    Ans: d

    49. In a pure inductive circuit
    (a) the current is in phase with the voltage
    (b) the current lags behind the voltage by 90°
    (c) the current leads the voltage by 90°
    (d) the current can lead or lag by 90°
    Ans: b

    50. In a circuit containing R, L and C, power loss can take place in
    (a) C only
    (b) L only
    (c) R only
    (d) all above
    Ans: c
  2. 51. Inductance of coil
    (a) is unaffected by the supply frequency
    (b) decreases with the increase in supply frequency
    (c) increases with the increase in supply frequency
    (d) becomes zero with the increase in supply frequency
    Ans: c

    52. In any A.C. circuit always
    (a) apparent power is more than actual power
    (b) reactive power is more than apparent power
    (c) actual power is more than reactive power
    (d) reactive power is more than actual power
    Ans: a

    53. Which of the following circuit component opposes the change in the circuit voltage ?
    (a) Inductance
    (b) Capacitance
    (c) Conductance
    (d) Resistance
    Ans:

    54. In a purely inductive circuit
    (a) actual power is zero
    (b) reactive power is zero
    (c) apparent power is zero
    (d) none of above is zero
    Ans: a

    55. Power factor of electric bulb is
    (a) zero
    (b) lagging
    (c) leading
    (d) unity
    Ans: d

    56. Pure inductive circuit takes power from the A.C. line when
    (a) applied voltage decreases but cur¬rent increases
    (b) applied voltage increases but cur¬rent decreases
    (c) both applied voltage and current increase
    (d) both applied voltage and current decrease
    Ans: a

    57. Time constant of a circuit is the time in seconds taken after the application of voltage to each
    (a) 25% of maximum value
    (b) 50% of maximum value
    (c) 63% of maximum value
    (d) 90% of the maximum value
    Ans: c

    58. Time constant of an inductive circuit
    (a) increases with increase of inductance and decrease of resistance
    (b) increases with the increase of inductance and the increase of resistance
    (c) increases with the decrease of inductance and decrease of resistance
    (d) increases with decrease of inductance and increase of resistance
    Ans: a

    59. Time constant of a capacitive circuit
    (a) increases with the decrease of capacitance and decrease of resistance
    (b) increases with the decrease of capacitance and increase of resis¬tance
    (c) increases with the increase of capacitance and decrease of resis¬tance
    (d) increase with increase of capacitance and increase of resis¬tance
    Ans: d

    60. Magnitude of current at resonance in R-L-C circuit
    (a) depends upon the magnitude of R
    (b) depends upon the magnitude of L
    (c) depends upon the magnitude of C
    (d) depends upon the magnitude of R, LandC
    Ans: a

    61. In a R-L-C circuit
    (a) power is consumed in resistance and is equal to I R
    (b) exchange of power takes place between inductor and supply line
    (c) exchange of power takes place between capacitor and supply line
    (d) exchange of power does not take place between resistance and the supply line
    (e) all above are correct
    Ans: e

    62. In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of
    (a) R only
    (b) L only
    (c) C only
    (d) L or C
    (e) R,L or C
    Ans: d

    63. In a series L-C circuit at the resonant frequency the
    (a) current is maximum
    (b) current is minimum
    (c) impedance is maximum
    (d) voltage across C is minimum
    Ans: a

    64. The time constant of a series R-C circuit is given by
    (a) R/C
    (b) RC2
    (c) RC
    (d) R2C
    Ans: c

    65. If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be
    (a) 0.001 s
    (b) 0.1 s
    (c) 10 s
    (d) 100 s
    Ans: b

    66. Which of the following coil will have large resonant frequency ?
    (a) A coil with large resistance
    (b) A coil with low resistance
    (c) A coil with large distributed capacitance
    (d) A coil with low distributed capacitance
    Ans: c

    67. If a sinusoidal wave has frequency of 50 Hz with 30 A r.m.s. current which of the following equation represents this wave ?
    (a) 42.42 sin 3141
    (b) 60 sin 25 t
    (c) 30 sin 50 t
    (d) 84.84 sin 25 t
    Ans: a

    68. The safest value of current the human body can carry for more than 3 second is
    (a) 4 mA
    (b) 9 mA
    (c) 15 mA
    (d) 25 mA
    Ans: b

    69. A pure inductance connected across 250 V, 50 Hz supply consumes 100 W.
    This consumption can be attributed to
    (a) the big size of the inductor
    (b) the reactance of the inductor
    (c) the current flowing in the inductor
    (d) the statement given is false
    Ans: d

    70. The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA
    The power drawn by the circuit is
    (a) 12 kW
    (b) 22 kW
    (c) 32 kW
    (d) 64 kW
    Ans: c

    71. The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of
    (a) iron loss in core
    (b) skin effect
    (c) increase in temperature
    (d) capacitive effect between adjacent coil turns
    Ans: a

    72. In an AC. circuit, a low value of kVAR compared with kW indicates
    (a) low efficiency
    (b) high power factor
    (c) unity power factor
    (d) maximum load current
    Ans: b

    73. In AC. circuits, laminated iron is invariably used in order to
    (a) reduce eddy current loss
    (b) increase heat radiation
    (c) make assembly cheap and easier
    (d) reduce circuit permeability
    Ans: a

    74. The ratio of active power to apparent power is known as factor.
    (a) demand
    (b) load
    (c) power
    (d) form
    Ans: c

    75. All definitions of power factor of a series R-L-C circuit are correct except
    (a) ratio of net reactance and impedance
    (b) ratio of kW and kVA
    (c) ratio of J and Z
    (d) ratio of W and VA
    Ans: a

    76. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is
    (a) 4 kVAR
    (b) 6 kVAR
    (c) 8 kVAR
    (d) 16 kVAR
    Ans: b

    77. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?
    (a) 0°
    (b) 45°
    (c) 90°
    (d) 180°
    Ans: c

    78. The purpose of a parallel circuit resonance is to magnify
    (a) current
    (b) voltage
    (c) power
    (d) frequency
    Ans: b

    79. In an A.C. circuit power is dissipated in
    (a) resistance only
    (b) inductance only
    (c) capacitance only
    (d) none of the above
    Ans: a

    80. In a parallel R-C circuit, the current always______the applied voltage
    (a) lags
    (b) leads
    (c) remains in phase with
    (d) none of the above
    Ans: b

    81. At very low frequencies a series R-C circuit behaves as almost purely
    (a) resistive
    (b) inductive
    (c) capacitive
    (d) none of the above
    Ans: c

    82. Skin effect occurs when a conductor carries current at _____ frequencies.
    (a) very low
    (b) low
    (c) medium
    (d) high
    Ans: d

    83. At ______ frequencies the parallel R-L circuit behaves as purely resistive.
    (a) low
    (b) very low
    (c) high
    (d) very high
    Ans: d

    84. In a sine wave the slope is constant
    (a) between 0° and 90°
    (b) between 90° and 180°
    (c) between 180° and 270°
    (d) no where
    Ans: d

    85. The power is measured in terms of decibles in case of
    (a) electronic equipment
    (b) transformers
    (c) current transformers
    (d) auto transformers
    Ans: a

    86. Capacitive susceptance is a measure of
    (a) reactive power in a circuit
    (b) the extent of neutralisation of reactive power in a circuit
    (c) a purely capacitive circuit's ability to pass current
    (d) a purely capacitive circuit's ability to resist the flow of current
    Ans: c

    87. Which of the following statements pertains to resistors only ?
    (a) can dissipate considerable amount of power
    (6) can act as energy storage devices
    (c) connecting them in parallel in¬creases the total value
    (d) oppose sudden changes in voltage
    Ans: a

    88. Which of the following refers to a parallel circuit ?
    (a) The current through each element is same
    (b) The voltage across element is in proportion to it's resistance value
    (c) The equivalent resistance is greater than any one of the resistors
    (d) The current through any one element is less than the source current
    Ans: d

    89. Aphasoris
    (a) a line which represents the mag¬nitude and phase of an alternating quantity
    (b) a line representing the magnitude and direction of an alternating quantity
    (c) a coloured tag or band for distinction between different phases of a 3-phase supply
    (d) an instrument used for measuring phases of an unbalanced 3-phase load
    Ans: a

    89. A parallel AC. circuit in resonance will
    (a) have a high voltage developed across each inductive and capacitive section
    (b) have a high impedance
    (c) act like a resistor of low value
    (d) have current in each section equal to the line current
    Ans: b

    90. Wire-wound resistors are unsuitable for use at high frequencies because they
    (a) create more electrical noise
    (b) are likely to melt under excessive eddy current heat
    (c) consume more power
    (d) exhibit unwanted inductive and capacitive effects
    Ans: d
  3. 91. The inductance of a coil can be increased by
    (a) increasing core length
    (b) decreasing the number of turns
    (c) decreasing the diameter of the former
    (d) choosing core material having high relative permeability
    Ans: d

    92. In a three-phase supply floating neutral is undesirable because it way give rise to
    (a) high voltage across the load
    (b) low voltage across the load
    (c) unequal line voltages across the load
    Ans: c

    93. Which of the following waves has the highest value of peak factor ?
    (a) Square wave
    (b) Sine wave
    (c) Half wave rectified sine wave
    (d) Triangular wave
    Ans: c

    94. The frequency of domestic power supply in India is
    (a) 200 Hz
    (b) 100 Hz
    (c) 60 Hz
    (d) 50 Hz
    Ans: d

    95. The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC. will be
    (a) 282.8 V
    (b) 141.4 V
    (c) 111 V
    (d) 100 V
    Ans: a

    96. The r.m.s. value of pure cosine function is
    (a) 0.5 of peak value
    (b) 0.707 of peak value
    (c) same as peak value
    (d) zero
    Ans: b

    97. Ohm is unit of all of the following except
    (a) inductive reactance
    (b) capacitive reactance
    (c) resistance
    (d) capacitance
    Ans: d

    98. The series ;nd parallel resonance on L-C circui' differs in that
    (a) series resistance needs a low-resistance ource for sharp rise in current
    (b) series resonance needs a high-resistance source for sharp increase in current
    (c) parallel resonance needs a low-resistance source for a sharp in¬crease in impedance
    (d) parallel resonance needs a low-resistance source for a sharp rise in line current
    Ans: a

    99. The phasors for which of the following pair are 180° out of phase for VL, VC and VR?
    (a) Vc and VR
    (b) VL and VR
    (c) Vc and VL
    (d) none of the above
    Ans: c

    100. The frequency of an alternating current is
    (a) the speed with which the alternator runs
    (b) the number of cycles generated in one minute
    (c) the number of waves passing through a point in one second
    (d) the number of electrons passing through a point in one second
    Ans: c

    101. A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to
    (a) the capacitive reactance in ohms
    (b) the current flowing in capacitor
    (c) the size of the capacitor being quite big
    (d) the statement is incorrect
    Ans: d

    102. The power factor of a D.C. circuit is always
    (a) less than unity
    (b) unity
    (c) greater than unity
    (d) zero
    Ans: b

    103. The product of apparent power and cosine of the phase angle between circuit voltage and current is
    (a) true power
    (b) reactive power
    (c) volt-amperes
    (d) instantaneous power
    Ans: a

    104. The equation of 50 Hz current sine wave having r.m.s. value of 60 A is
    (a) 60 sin 25 t
    (b) 60 sin 50 t
    (c) 84.84 sin 3141
    (d) 42.42 sin 314 t
    Ans: c

    105. An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,
    (a) the current through the resistance is more
    (b) the current through the resistance is less
    (c) both resistance and inductance carry equal currents
    (d) none of the above
    Ans: c

    106. In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will
    (a) be reduced by half
    (b) be doubled
    (c) be four times as high
    (d) be reduced to one fourth
    Ans: b

    107. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will
    (a) be reduced by half
    (b) be doubled
    (c) be four times at high
    (d) be reduced to one fourth
    Ans: a

    108. When an alternating current passes through an ohmic resistance the electrical power converted into heat is
    (a) apparent power
    (b) true power
    (c) reactive power
    (d) none of the above
    Ans: b

    109. In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value of 220 V is induced. Which of the following values is indicated by the voltmeters ?
    (a) 220 V
    (b) 220V3V
    (c) 220/V3 V
    (d) none of the above
    Ans: a


    110. Laminations of core are generally made of
    (a) case iron
    (b) carbon
    (c) silicon steel
    (d) stainless steel

    1Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be
    (a) 270 V
    (b) 267.5 V
    (c) 265 V
    (d) 257.4 V
    Ans: b

    Ans: c
    2. Which of the following could be lamina-proximately the thickness of lamina-tions of a D.C. machine ?
    (a) 0.005 mm
    (b) 0.05 mm
    (c) 0.5 m
    (d) 5 m
    Ans: c


    3. The armature of D.C. generator is laminated to
    (a) reduce the bulk
    (b) provide the bulk
    (c) insulate the core
    (d) reduce eddy current loss
    Ans: d


    4. The resistance of armature winding depends on
    (a) length of conductor
    (b) cross-sectional area of the conductor
    (c) number of conductors
    (d) all of the above
    Ans: d


    5. The field coils of D.C. generator are usually made of
    (a) mica
    (b) copper
    (c) cast iron
    (d) carbon
    Ans: b


    6. The commutator segments are connected to the armature conductors by means of
    (a) copper lugs
    (b) resistance wires
    (c) insulation pads
    (d) brazing
    Ans: a

    7. In a commutator
    (a) copper is harder than mica
    (b) mica and copper are equally hard
    (c) mica is harder than copper
    (d) none of the above
    Ans: c

    8. In D.C. generators the pole shoes are fastened to the pole core by
    (a) rivets
    (b) counter sunk screws
    (c) brazing
    (d) welding
    Ans: b

    9. According to Fleming's right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of
    (a) motion of conductor
    (b) lines of force
    (c) either of the above
    (d) none of the above
    Ans: b

    10. Fleming's right-hand rule regarding direction of induced e.m.f., correlates
    (a) magnetic flux, direction of current flow and resultant force
    (b) magnetic flux, direction of motion and the direction of e.m.f. induced
    (c) magnetic field strength, induced voltage and current
    (d) magnetic flux, direction of force and direction of motion of conductor
    Ans: b

    11. While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards
    (a) direction of induced e.m.f.
    (b) direction of flux
    (c) direction of motion of the conductor if forefinger points in the direction of generated e.m.f.
    (d) direction of motion of conductor, if forefinger points along the lines of flux
    Ans: d

    12. The bearings used to support the rotor shafts are generally
    (a) ball bearings
    (b) bush bearings
    (c) magnetic bearmgs
    (d) needle bearings
    Ans: a

    13. In D.C. generators, the cause of rapid brush wear may be
    (a) severe sparking
    (b) rough commutator surface
    (c) imperfect contact
    (d) any of the above
    Ans: d

    14. In lap winding, the number of brushes is always
    (a) double the number of poles
    (b) same as the number of poles
    (c) half the number of poles
    (d) two
    Ans: b

    15. For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?
    (a) Lap winding
    (b) Wave winding
    (c) Either of (a) and (b) above
    (d) Depends on other features of design
    Ans: b

    16. In a four-pole D.C. machine
    (a) all the four poles are north poles
    (b) alternate poles are north and south
    (c) all the four poles are south poles
    (d) two north poles follow two south poles
    Ans: b

    17. Copper brushes in D.C. machine are used
    (a) where low voltage and high currents are involved
    (b) where high voltage and small cur-rents are involved
    (c) in both of the above cases
    (d) in none of the above cases
    Ans: a

    18. A separately excited generator as compared to a self-excited generator
    (a) is amenable to better voltage con-trol
    (b) is more stable
    (c) has exciting current independent of load current
    (d) has all above features
    Ans: d

    19. In case of D.C. machines, mechanical losses are primary function of
    (a) current
    (b) voltage
    (c) speed
    (d) none of above
    Ans: c

    20. Iron losses in a D.C. machine are independent of variations in
    (a) speed
    (b) load
    (c) voltage
    (d) speed and voltage
    Ans: b

    21. In D.C. generators, current to the external circuit from armature is given through
    (a) commutator
    (b) solid connection
    (c) slip rings
    (d) none of above
    Ans: a

    23. Brushes of D.C. machines are made of
    (a) carbon
    (b) soft copper
    (c) hard copper
    (d) all of above
    Ans: a

    24. If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by
    (a)Blv
    (b)Blv2
    (c)Bl2v
    (d)Bl2v2
    Ans: a

    25. In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be
    (a) 4
    (b) 8
    (c) 16
    (d) 32
    Ans: b

    26. The material for commutator brushes is generally
    (a) mica
    (b) copper
    (c) cast iron
    (d) carbon
    Ans: d

    27. The insulating material used between the commutator segments is normally
    (a) graphite
    (b) paper
    (c) mica
    (d) insulating varnish
    Ans: c

    28. In D.C. generators, the brushes on commutator remain in contact with conductors which
    (a) lie under south pole
    (b) lie under north pole
    (c) lie under interpolar region
    (d) are farthest from the poles
    Ans: c

    29. If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be
    (a) demagnetisation only
    (b) cross magnetisation as well as magnetisation
    (c) crossmagnetisation as well as demagnetising
    (d) cross magnetisation only
    Ans: c

    30. Armature reaction of an unsaturated D.C. machine is
    (a) crossmagnetising
    (b) demagnetising
    (c) magnetising
    (d) none of above
    Ans: a
  4. 31. D.C. generators are connected to the busbars or disconnected from them only under the floating condition
    (a) to avoid sudden loading of the primemover
    (b) to avoid mechanicaljerk to the shaft
    (c) to avoid burning of switch contacts
    (d) all above
    Ans: d

    32. Eddy currents are induced in the pole shoes of a D.C. machine due to
    (a) oscillating magnetic field
    (b) pulsating magnetic flux
    (c) relative rotation between field and armature
    (d) all above
    Ans: c

    33. In a D.C. machine, short-circuited field coil will result in
    (a) odour of barning insulation
    (b) unbalanced magnetic pull producing vibrations
    (c) reduction of generated voltage for which excitation has to be increased to maintain the voltage
    (d) all above
    Ans:

    34. Equilizer rings are required in case armature is
    (a) wave wound
    (b) lap wound
    (c) delta wound
    (d) duplex wound
    Ans: b

    35. Welding generator will have
    (a) lap winding
    (b) wave winding
    (c) delta winding
    (d) duplex wave winding
    Ans: a

    36. In case of D.C. machine winding, number of commutator segments is equal to
    (a) number of armature coils
    (b) number of armature coil sides
    (c) number of armature conductors
    (d) number of armature turns
    Ans: a

    37. For a D.C. machines laboratory following type of D.C. supply will be suitable
    (a) rotary converter
    (b) mercury are rectifier
    (c) induction motor D.C. generator set
    (d) synchronous motor D.C. generator set
    Ans: c

    38. The function of pole shoes in the case of D.C. machine is
    (a) to reduce the reluctance of the magnetic path
    (b) to spread out the flux to achieve uniform flux density
    (c) to support the field coil
    (d) to discharge all the above functions
    Ans: d

    39. In the case of lap winding resultant pitch is
    (a) multiplication of front and back pitches
    (b) division of front pitch by back pitch
    (c) sum of front and back pitches
    (d) difference of front and back pitches
    Ans: d

    40. A D.C. welding generator has
    (a) lap winding
    (b) wave moving
    (c) duplex winding
    (d) any of the above
    Ans: a

    41. Which of the following statement about D.C. generators is false ?
    (a) Compensating winding in a D.C. machine helps in commutation
    (b) In a D. C. generator interpoles winding is connected in series with the armature winding
    (c) Back pitch and front pitch are both odd and approximately equal to the pole pitch
    (d) Equilizing bus bars are used with parallel running of D.C. shunt generators
    Ans: d

    42. The demagnetising component of armature reaction in a D.C. generator
    (a) reduces generator e.m.f.
    (b) increases armature speed
    (c) reduces interpoles flux density
    (d) results in sparking trouble
    Ans: a

    43. Magnetic field in a D.C. generator is produced by
    (a) electromagnets
    (b) permanent magnets
    (c) both (a) and (b)
    (d) none of the above
    Ans: a

    44. The number of brushes in a commutator depends on
    (a) speed of armature
    (b) type of winding
    (c) voltage
    (d) amount of current to be collected
    Ans: d

    45. Compensating windings are used in D.C. generators
    (a) mainly to reduce the eddy currents by providing local short-circuits
    (b) to provide path for the circulation of cooling air
    (c) to neutralise the cross-magnetising effect of the armature reaction
    (d) none of the above
    Ans: c

    46. Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?
    (a) Dummy coils
    (b) Commutator
    (c) Eye bolt
    (d) Equilizer rings
    Ans: b

    47. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by
    (a) using conductor of annealed copper
    (b) using commutator with large number of segments
    (c) using carbon brushes of superior quality
    (d) using equiliser rings
    Ans: c

    48. In D.C. generators, lap winding is used for
    (a) high voltage, high current
    (b) low voltage, high current
    (c) high voltage, low current
    (d) low voltage, low current
    Ans: b

    49. Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be
    (a) 2 : 3
    (b) 3 : 1
    (c) 3 : 2
    (d) 1 : 3
    Ans: b

    50. The voltage drop for which of the following types of brush can be expected to be least ?
    (a) Graphite brushes
    (b) Carbon brushes
    (c) Metal graphite brushes
    (d) None of the above
    Ans: c

    51. The e.m.f. generated by a shunt wound D.C. generator isE. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be
    (a) E/2
    (b) 2E
    (c) slightly less than E
    (d) E
    Ans: b

    52. In a D.C. generator the actual flux distribution depends upon
    (a) size of air gap
    (b) shape of the pole shoe
    (c) clearance between tips of the ad¬jacent pole shoes
    (d) all of the above
    Ans:

    53. The armature core of a D.C. generator is usually made of
    (a) silicon steel
    (b) copper
    (c) non-ferrous material
    (d) cast-iron
    Ans: a

    9.63. Satisfactory commutation of D.C. machines requires
    (a) brushes should be of proper grade and size
    (b) brushes should smoothly run in the holders
    (c) smooth, concentric commutator properly undercut
    (d) all of the above
    Ans: d

    54. Open circuited armature coil of a D.C. machine is
    (a) identified by the scarring of the commutator segment to which open circuited coil is connected
    (b) indicated by a spark completely around the commutator
    (c) both (a) and (b)
    (d) none of the above
    Ans: c

    55. In a D.C. machine, fractional pitch winding is used
    (a) to increase the generated voltage
    (b) to reduce sparking
    (c) to save the copper because of shorter end connections
    (d) due to (b) and (c) above
    Ans:

    56. For the parallel operation of two or more D.C. compound generators, we should ensure that
    (a) voltage of the incoming generator should be same as that of bus bar
    (b) polarity of incoming generator should be same as that of bus bar
    (c) all the series fields should be run in parallel by means of equilizer connection
    (d) series fields of all generators should be either on positive side or negative side of the armature
    (e) all conditions mentioned above should be satisfied
    Ans: d

    57. D.C. series generator is used
    (a) to supply traction load
    (b) to supply industrial load at constant voltage
    (c) voltage at the toad end of the feeder
    (d) for none of the above purpose
    Ans: c

    58. Following D.C. generator will be in a position to build up without any residual magnetism in the poles
    (a) series generator
    (b) shunt generator
    (c) compound generator
    (d) self-excited generator
    Ans: d

    59. Interpole flux should be sufficient to
    (a) neutralise the commutating self induced e.m.f.
    (b) neutralise the armature reaction flux
    (c) neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil
    (d) perform none of the above functions
    Ans: c

    60. D.C. generator generally preferred for charging automobile batteries is
    (a) series generator
    (b) shunt generator
    (c) long shunt compound generator
    (d) any of'the above
    Ans: c

    61. In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when
    (a) r.p.m. is more than 300
    (b) r.p.m. is less than 300
    (c) number of poles is 4
    (d) number of poles is 2
    Ans: d

    62. Permeance is the reciprocal of
    (a) flux density
    (b) reluctance
    (c) ampere-turns
    (d) resistance
    Ans: b

    63. In D.C. generators the polarity of the interpoles
    (a) is the same as that of the main pole ahead
    (b) is the same as that of the immediately preceding pole
    (c) is opposite to that of the main pole ahead
    (d) is neutral as these poles do not play part in generating e.m.f.
    Ans: a

    64. The e.m.f. generated in a D.C. generator is directly proportional to
    (a) flux/pole
    (b) speed of armature
    (c) number of poles
    (d) all of the above
    Ans: b

    65. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when
    (a) there is no load on|he generator
    (b) the generator runs on full load
    (c) the generator runs on overload
    (d) the generator runs on designed speed
    Ans: a

    66. In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except
    (a) interpoles
    (b) dummy coils
    (c) compensating winding
    (d) shifting of axis of brushes
    Ans: b

    67. In D.C. generators on no-load, the air gap flux distribution in space is
    (a) sinusoidal
    (b) triangular
    (c) pulsating
    (d) flat topped
    Ans: d

    68. A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly
    (a) 150 V
    (b) 175 V
    (c) 240 V
    (d) 290 V
    Ans: c

    69. The purpose of providing dummy coils in a generator is
    (a) to reduce eddy current losses
    (b) to enhance flux density
    (c) to amplify voltage
    (d) to provide mechanical balance for the rotor
    Ans: d

    70. In a shunt generator the voltage build up is generally restricted by
    (a) speed limitation
    (b) armature heating
    (c) insulation restrictions
    (d) saturation of iron
    Ans:

    71. If a D.C. generator fails to build up the probable cause could not be
    (a) imperfect brush contact
    (b) field resistance less than the critical resistance
    (c) no residual magnetism in the generator
    (d) faulty shunt connections tending to reduce the residual magnetism
    Ans: b

    72. Flashing the field of D.C. generator means
    (a) neutralising residual magnetism
    (b) creating residual magnetism by a D.C. source
    (c) making the magnetic losses of forces parallel
    (d) increasing flux density by adding extra turns of windings on poles
    Ans: b

    73. The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be
    (a) 640 V
    (b) 620 V
    (c) 600 V
    (d) 580 V
    Ans: d
  5. 74. In a D.C. generator the critical resistance refers to the resistance of
    (a) brushes
    (b) field
    (c) armature
    (d) load
    Ans: b

    75. To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them
    (a) just ahead of magnetic neutral axis
    (b) in magnetic neutral axis
    (c) just behind the magnetic neutral axis
    Ans: a

    76. Armature coil is short circuited by brushes when it lies
    (a) along neutral axis
    (b) along field axis
    (c) in any of the above positions
    (d) in none of the above positions
    Ans: a

    77. A cumulatively compounded long shunt generator when operating as a motor would be
    (a) cumulatively compounded long shunt
    (b) differentially compounded long shunt
    (c) cumulatively compounded short shunt
    (d) differentially compounded short shunt
    Ans: b

    78. To avoid formation of grooves in the commutator of a D.C. machine
    (a) the brushes of opposite polarity should track each other
    (b) the brushes of same polarity should track each other
    (c) brush position has no effect on the commutator grooving
    Ans: a

    79. The following constitute short-circuit in the armature winding.
    (a) Insulation failure between two com-mutator bars
    (6) Insulation failure between two turns of a coil
    (c) Two of more turns of the same coil getting grounded
    (d) All of the above
    Ans: d

    80. The rapid wear of brushes takes place due to
    (a) abrasion from dust
    (b) excessive spring pressure
    (c) rough commutator bars
    (d) high mica insulation between com-mutation bars
    (e) all of the above factors
    Ans: e

    81. Number of tappings for each equilizer ring is equal to
    (a) number of pole pairs
    (b) number of poles
    (c) number of parallel paths
    (d) number of commutator segments
    Ans: a

    82. A D.C. generator can be considered as
    (a) rectifier
    (b) primemover
    (c) rotating amplifier
    (d) power pump
    Ans: c

    83. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called
    (a) rotor
    (b) stator
    (c) field
    (d) armature
    Ans: d

    84. In a D.C. machine stray loss is the sum of
    (a) total copper loss and mechanical loss
    (b) armature copper loss and iron loss
    (c) shunt field copper loss and mechanical loss
    (d) iron loss and mechanical loss
    Ans: d

    85. Lap winding is composed of
    (a) any even number of conductors
    (b) any odd number of conductors
    (c) that even number which is exact multiple of poles + 2
    (d) that even number which is exact multiple of poles
    Ans: a

    86. In a D.C. generator in case the resistance of the field winding is increased, then output voltage will
    (a) increase
    (b) decrease
    (c) remain unaffected
    (d) fluctuate heavily
    Ans: b

    87. An exciter for a turbo generator is a
    (a) separately excited generator
    (b) shunt generator
    (c) series generator
    (d) compound generator
    Ans: b

    88. In case of a flat compounded generator
    (a) voltage generated is less than the rated voltage
    (b) generated voltage is proportional to the load on the generator
    (c) voltage remains constant irrespec¬tive of the load
    (d) speed varies in proportion to the load on the generator
    Ans: c

    89. Which of the following generator will have negligible terminal voltage while running on no-load ?
    (a) Series generator
    (b) Shunt generator
    (c) Compound generator
    (d) Separately excited generator
    Ans: a

    90. Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ?
    (a) Series generator
    (b) Shunt generator
    (c) Compound generator
    (d) None of the above
    Ans: d

    91. In over compounded generator, full load terminal voltage is
    (a) almost zero
    (b) less than noload terminal voltage
    (c) more than noload terminal voltage
    (d) equal to no-load terminal voltage
    Ans: c

    92. In a level compounded D.C. generator, full load terminal voltage is
    (a) negligibly low
    (b) equal to no-load terminal voltage
    (c) more than no-load terminal voltage
    (d) less than no-load terminal voltage
    Ans: b

    93. The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except
    (a) armature reaction
    (b) armature resistance drop
    (c) field weakening due to armature reaction and armature
    (d) commutation
    Ans: d

    94. In a D.C. generator
    (a) external resistance = internal char-acteristic - armature reaction
    (b) internal characteristic = magnetisation characteristic - ohmic drop
    (c) external characteristic = magnetisation characteristic - ohmic drop - armature reaction
    (d) magnetisation characteristic = external characteristic
    Ans: c

    95. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave
    (a) will be zero
    (b) will be of 5 Hz
    (c) willbeof5xiVHz
    (d) will be of v Hz 5
    Ans: b

    96. A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be
    (a) zero
    (b) about 2 V
    (c) about 50 V
    (d) 220 V
    Ans: b

    97. In a separately excited generator supplying rated load the armature reaction ,
    (a) is always present
    (b) is always absent
    (c) may be sometimes present
    (d) none of the above
    Ans: a

    98. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be
    (a) zero
    (b) small
    (c) the same as rated voltage
    (d) high
    Ans: a

    99. Armature reaction in a generator results in
    (a) demagnetisation of leading pole tip and magnetisation of trailing pole tip
    (b) demagnetisation of trailing pole tip and magnetisation of leading pole tip
    (c) damagnetising the centre of all poles
    (d) magnetising the centre of all poles
    Ans: a

    100. Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.
    (a) Series field
    (b) Compensating field
    (c) Inter pole field
    (d) Shunt field
    Ans: d

    101. Wave winding is composed of
    (a) any even number of conductors
    (b) any odd number of conductors
    (c) that even number which is exact multiple of poles + 2
    (d) that even number which is exact multiple of poles
    Ans: c

    102. The critical resistance of the D.C. generator is the resistance of
    (a) field
    (b) brushes
    (c) armature
    (d) load
    Ans: a

    103. When two D.C. series generators are running in parallel, an equilizer bar is used
    (a) to increase the speed and hence generated e.m.f.
    (b) to increase the series flux
    (c) so that two similar machines will pass approximately equal currents to the load
    (d) to reduce the combined effect of ar-mature reaction of both machines
    Ans: c

    104. Which of the following generating machine will offer constant voltage on all loads ?
    (a) Self-excited generator
    (b) Separately excited generator
    (c) Level compounded generator .
    (d) All of the above
    Ans: c

    105. Which of the following generators will be preferred if they are required to be run in parallel ?
    (a) Shunt generators
    (b) Series generators
    (c) Compound generators
    (d) None of the above
    Ans: a

    106. Two generators are running in parallel. One of the generators may run as motor for which of the following reasons ?
    (a) The direction of that generator is reversed
    (b) The speed of that generator is increased
    (c) The field of that generator is weakened
    (d) That generator takes large share of loads
    Ans: d

    107. A D.C. generator works on the principle of
    (a) Lenz's law
    (b) Ohm's law
    (c) Faraday's law of electromagnetic induction
    (d) none of the above
    Ans: c

    108. A series generator can self-excite
    (a) only if the load current is zero
    (b) only if the load current is not zero
    (c) irrespective of the value of load current
    (d) none of the above
    Ans: b

    109. A shunt generator can self-excite
    (a) only if the resistance of the field circuit is less than critical value
    (b) only if the resistance of the field circuit is greater than critical value
    (c) irrespective of the value of the resis-tance in the field circuit
    Ans: a

    110. The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be
    (a) 150 V
    (b) less than 150 V
    (c) greater than 150 V
    (d) none of the above
    Ans: c

    111. The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage
    (a) will be less than 250 V
    (b) will always be 250 V
    (c) may be greater or less than 250 V
    (d) none of the above
    Ans: c

    112. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be
    (a) 270 V
    (b) 267.5 V
    (c) 265 V
    (d) 257.4 V
    Ans: b

    113. The essential condition for parallel operation of two D.C. generators is that they have '
    (a) same kW rating
    (b) the same operation r.p.m.
    (c) the same drooping voltage charac-teristics
    (d) same percentage regulation
    Ans: c

    114. When two D.C. generators are running in parallel an equilizer bar is used
    (a) to increase the series flux
    (b) to increase the generated e.m.f.
    (c) to reduce the combined effect of ar-mature reaction of both the machines
    (d) so that the two identical machines will pass approximately equal currents to the load
    Ans: d

    115. With a D.C. generator which of the following regulation is preferred ?
    (a) 100% regulation
    (b) infinite regulation
    (c) 50% regulation
    (d) 1% regulation
    Ans: d

    116. Which generator would you prefer for feeding long D.C. transmission lines ?
    (a) Series generator
    (b) Shunt generator
    (c) Over compound generator
    (d) Flat compound generator
    Ans: c

    117. In a D.C. generator the critical resistance can be increased by
    (a) increasing its field resistance
    (b) decreasing its field resistance
    (c) increasing its speed
    (d) decreasing its speed
    Ans: c

    118. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is
    (a) 2
    (b) 4
    (c) 6
    (d) 8
    Ans: b

    119. For both lap and wave windings, there are as many commutator bars as the number of
    (a) slots
    (b) armature conductors
    (c) winding elements
    (d) poles
    Ans: c
  6. 120. The series field of a short-shunt D.C. generator is excited by
    (a) external current
    (b) armature current
    (c) shunt current
    (d) load current
    Ans: d

    121. As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately
    (a) 40 percent
    (b) 25 percent
    (c) 10 percent
    (d) 5 percent
    Ans: d

    122. Shunt generators are most suited for stable parallel operation because of their
    (a) rising voltage characteristics
    (b) identical voltage characteristics
    (c) drooping voltage characteristics
    (d) linear voltage characteristics
    Ans: c

    123. The main factor which leads to unstable parallel operation of flat and over compounded generators is
    (a) their rising voltage characteristics
    (b) unequal number of turns in their series field windings
    (c) unequal speed regulation of their primemovers
    (d) unequal series field resistances
    Ans: a

    124. If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to
    (a) reverse the field connections
    (b) increase the field resistance
    (c) increase the speed of primemover
    (d) check armature insulation resis¬tance
    Ans: a

    125.The essential condition for parallel operation of two D.C. generators is that they have '
    (a) same kW rating
    (b) the same operation r.p.m.
    (c) the same drooping voltage charac-teristics
    (d) same percentage regulation
    Ans: c

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