This is the question paper of ISRO for scientist job conducted on may 2017. check out this questions.
1) The starting torque of three phase induction motor can be increased by
A) Increasing rotor reactance
B) Increasing rotor resistance
C) Increasing stator resistance
D) None of the above
Ans:B
2) The capacitor start capacitor run single phase induction motor is operationally a
A) Single phase motor
B) Two phase motor
C) Three phase motor
D) A.C Series motor
Ans:B
3) What would happen if the field of a D.C shunt motor is opened?
A) Speed will be reduced
B) Continue to run normally
C) Speed will enormously increase damaging the motor
D) None of the above
Ans:C
4) Equalizer rings in D.C generator with lap windings are used for
A) Equal distribution of current at brush for sparkless commutation
B) prevention of harmonics
C) Reduction of noise and vibration
D) Avoiding overhang
Ans:A
5) The Buchholz relay is normally used to protect the
A) Alternator against all internal faults
B) Oil immersed transformers against all internal faults
C) Synchronous motors against all internal faults
D) Transmission lines against all short circuit faults
Ans:B
6) A 400/200 volts transformer has pu impedence of 0.05. The HV side voltage required to circulate full load current during short circuit test is
A) 20 V
B) 40 V
C) 10 V
D) 5 V
Ans:A
7) Non-loading heat run test on transformer is performed by means of
A) SC test
B) OC test
C) core balance test
D) sumpner's test
Ans:D
8) A three phase induction motor is driving full load torque which is independent of speed. If the lines voltage drops to 90% of rated value, % increase in motor copper losses
A) 23%
B) -18%
C) 123%
D) None of these
Ans:A
9) A synchronous generator is feeding power to infinite bus bars at unity power factor. Its excitation is now increased. It will feed
A) The same power but at a leading power factor
B) The same power but at a lagging power factor
C) More power at unity power factor
D) Less power at unity power factor
Ans:B
10) The steam input into a turbo generator connected to infinite bus is increased. which of the events will take place?
A) The generator will feed more leading KVAR to bus bar and power angle will not change.
B) The generator will feed more real power to bus bar and power angle will increase.
C) The generator will feed more power to bus bar and power angle will decrease.
D) The generator will feed more lagging KVAR to bus bar and power angle will not change.
Ans:B
11) Copper behaves as a
A) Conductor always
B) Conductor or dielectric depending on field strength
C) Conductor or dielectric depending on frequency
D) Conductor or dielectric depending on the electric current density
Ans:A
12) Assuming constant transmission efficiency, if voltage is increased 'n' times, the size of the conductor would be
A) Reduced to 1/n^2 that of the original
B) Increased to n^2 that of the original
C) Reduced to 1/n that of the original
D) Increased to n times that of the original
Ans:A
13) Shunt conductance in overhead power transmission lines is primarily due to
A) Leakage over the insulators
B) Leakage over the conductors
C) Leakage over the poles
D) Leakage between ground and conductors
Ans:A
14) The dielectric strength of SF6 gas (used in circuit breakers) is approximately
A) Same as that of air
B) 2 to 3 times more than air
C) 10 to 20 times more than air
D) 2 to 3 times less than air
Ans:B
15) Ferranti effect states that under certain conditions, the sending end voltage is
A) Less than receiving end voltage
B) More than receiving end voltage
C) Equal to receiving end voltage
D) Not having any impact on the receiving end voltage
Ans:A
16) Over fluxing protection is normally recommended for
A) Generator transformers in power stations
B) Auto-transformers in power stations
C) Stations transformers in power stations
D) Distribution transformers
Ans:A
17) In general AC distribution systems, arc interruption in vaccum circuit breakers are designed to function in a time period of
A) One cycle
B) Two to three cycles
C) Within ten cycles
D) None of the above
Ans:A
18) Systems for Protection from negative-sequence current is provided normally for
A) Transformers
B) Generators
C) Transmission lines
D) Motors
Ans:B
19) Bundled conductors are mainly used in high voltage overhead transmission lines to
A) Reduced line loss
B) Reduced harmonics
C) Reduced corona
D) Increase strength
Ans:C
20) Surge impedence of overhead transmission line is normally in the order of
A) 1-5 ohms
B) 20-30 ohms
C) 300-500 ohms
D) 300000-500000 ohms
Ans:C
21) The bode diagram approach is applied to
A) Non-minimum phase network
B) Minimum phase network
C) Any network of a control system
D) None of the above
Ans:B
22) An ON-OFF controller is
A) P controller
B) Integral controller
C) Non-linear controller
D) PID controller
Ans:C
23) The transfer function of a phase lead controller is (1+3Ts)/(1+Ts). The maximum value of phase provided by this controller is
A) 90
B) 60
C) 45
D) 30
Ans:D
24) The thermal time constant is the time
A) To reach the final steady temperature if the initial rate of increase of temperature were maintained constant
B) To reach 63% of final steady temperature
C) To reach 66.66% of final steady temperature
D) To reach half of the final steady temperature
Ans:A
25)Which of the following circuit has no transients?
A) Pure resistive circuit
B) L-C Circuit
C) R-L-C Circuit
D) R-L Circuit
Ans:A
26) A conductor of length 100 cms moves right angles to a magnetic field of flux density of 2 wb/sq.m. with the velocity of 25m/second. The induced emf in the conductor will be
A) 25 Volts
B) 50 Volts
C) 75 Volts
D) 100 Volts
Ans:B
27) The core of a moving iron instrument is made up of permalloy to
A) Increase sensitivity
B) Reduced temperature effect
C) Reduced effect of stray magnetic field
D) Reduced the size of the instrument
Ans:A
28) Accuracy is defined as
A) The measure of consistency of the readings
B) Closeness with which an instrument reading approaches the true value of the quantity being measured
C) The smallest measurable input change
D) The ratio of the input to output
Ans:B
29) If three amplifiers having the same bandwidth are cascaded, the bandwidth of the resulting amplifier will be
A) Better than that of each stage
B) Worse than that of each stage
C) Same as that of each stage
D) None of the above
Ans:B
30) An element is said to have negative resistance when
A) The element has negative tempeature coefficient.
B) The current/voltage curve has negative slope
C) The element has negative specific resistance
D) The current/ voltage curve has a positive slope
Ans:B
31) An ideal rectifier should have transformer utilization factor (TUF) of 1. If the actual TUF is 3.5, it shows that
A) Diode is under-loaded
B) The transformer must be 3.5 times larger
C) The transformer should be only 1/3.5 times the ideal size
D) The ripple factor is low
Ans:B
32) A power MOSFET is a
A) Voltage controlled device
B) Current controlled device
C) frequency controlled device
D) None of the above
Ans:A
33) When transistors are used in series or parallel, a snubber circuit is used to
A) Control the current
B) Control the voltage
C) Limit di/dt
D) All of these
Ans:C
34)
is equal to
A) -∞
B) 0
C) 1
D) ∞
Ans:C
35) A fair (unbiased) coin was tossed four times in succession and resulted in the following outcomes: (i) Head (ii) Head (iii) Head (iv) Head. The probability of getting a "Tail" when the coin is tossed again is
A) 0
B) 1/2
C) 4/5
D) 1/5
Ans:B
36) Using trapezoidal rule for the table given below ∫lnx dx with limits 5.2 to 4 will be
x : 4 4.2 4.4 4.6 4.8 5.0 5.2
lnx: 1.39 1.44 1.48 1.53 1.57 1.61 1.65
A) 1.8277
B) 1.9284
C) 1.6424
D) 0.98795
Ans:A
37) Find the z transform of (n+1)^2
A) z^2(2z+1)/(z-1)^3
B) (2z+1)/(z-1)^3
C) (2+z)/(z-1)^2
D) (3z+2)/(z-1)
Ans:A
38) Consider the following system of euations in three real variables x1,x2 and x3
2x1-x2+3x3=1
3x1-2x2+5x3=2
-x1-4x2+x3=3
The system of equations has
A) No solutions
B) A unique solution
C) More than one but a finite number of solutions
D) An infinite number of solutions
Ans:B
39) Which of the following functions would have only odd powers of x in its Taylors series expansion about the point x=0?
A) sin(x^3)
B) sin(x^2)
C) cos(x^3)
D) cos(x^2)
Ans:A
40) An inductance of one H carying a current of two amperes will store the energy of
A) 2 watts
B) 2 joules
C) 4 watts
D) 4 joules
Ans:B
41) The square waveform of current has following relation between r.m.s value and average value
A) r.m.s value of current is greater than the average value
B) r.m.s value of current is less than the average value
C) r.m.s value of current is equal to the average value
D) There is no definite relation between the r.m.s value and average value for a square wave
Ans:C
42) Two numbers of 500 ohms one watt resistors are connected in parallel. Their combined resistance and wattage rating will be
A) 250 ohms, 1 watt
B) 250 ohms, 2 watts
C) 1000 ohms, 2 watts
D) 500 ohms, 2 watts
Ans:B
43) In a long uniform coil of inductance 2L and associated resistance 2R ohms is physically cut in to two exact halves which are rewound in parallel. The resistance and inductance of the combination are
A) R and L
B) 2R and 2L
C) R/2 and L/2
D) R/4 and L/4
Ans:C
44) For transfer function of a physical two-port network
A) All zeros must lie only in the left half of the s-plane
B) All poles may lie anywhere in the s-plane
C) The poles lying on the imaginary axis must be simple
D) All the above
Ans:D
45) The power transformer is a
A) Constant current device
B) Constant voltage device
C) Constant frequency device
D) Pulsating main flux device
Ans:D
46) A change of 5% in supply voltage to an induction motor will produce a change of approximately
A) 5% in the rotor torque
B) 7.5% in the rotor torque
C) 10% in the rotor torque
D) 25% in the rotor torque
Ans:D
47) If the supply frequency to the transformer is increased, the iron loss
A) will increase
B) will decrease
C) will not change
D) may reach zero
Ans:A
48) The maximum temperature permitted for class A insulation is
A) 180 degree centigrade
B) 105 degree centigrade
C) 120 degree centigrade
D) None of the above
Ans:B
49) Two transformers connected in parallel share load in the ratio of their KVA ratings, provided their ohmic impedence are
A) Equal
B) In direct ratio of their ratings
C) In inverse ratio of their ratings
D) Purely reactive
Ans:C
50) The high frequency hum in the transformer is mainly due to
A) Loose laminations
B) Magnetostriction
C) Impurity in oil
D) Weakness of tank wall
Ans:B
51) In an ideal transformer, which of the following statement is correct?
A) no voltage drops in resistance or leakage reactance
B) mmf required to maintain main flux is small
C) no core loss
D) all the above are correct
Ans:D
52) The voltage applied to a transformer primary is increased keeping v/f fixed. How will core loss and magnetising current change
A) Core loss will increase and magnetizing current remain same
B) Core loss will remain same and magnetizing current will remain same
C) Core loss will decrease and magnetizing current will increase
D) Core loss will remain same and magnetizing current will decrease
Ans:A
53) Frequency in the UHF range normally propagate by means of
A) Ground waves
B) Sky waves
C) Surface waves
D) Space waves
Ans:D
54) Indicate the antenna that is not wideband
A) Discone
B) Folded dipole
C) Helical
D) Marconi
Ans:D
55) The depth of penetration of a wave in a lossy dielectric increases with increasing
A) Conductivity
B) Permeability
C) Wavelength
D) Permittivity
Ans:C
56) The equal area criterion of stability is applicable to
A) Two machine system and infinite bus bars
B) One machine system and infinite bus bars
C) Multi-machine system only
D) None of the above
Ans:B
57) The power transmisssion capacity of the transmission line is
A) Inversely proportional to the square of the voltage
B) Proportional to the voltage
C) Inversely proportional to the voltage
D) Proportional to the square of the operating voltage
Ans:D
58) If the torque angle 'delta' increases indefinitely, the system indicates
A) Steady state stability
B) Permanent stability
C) Instability
D) None of the above
Ans:C
59) Resistance switching is normally employed in
A) All breakers
B) Bulk oil breaker
C) Minimum oil breaker
D) Air-blast circuit breaker
Ans:D
60) Series capacitors are used to
A) Improve line frequency and eliminate harmonics
B) Compensation for line inductance reactance
C) Neutralise line capacitive reactance
D) None of the above
Ans:B
61) Which of the following methods is the strongest tool to determine the stability and the transient response of the system?
A) Routh-Hurwitz criterion
B) Bode plot
C) Nyquist plot
D) Root locus
Ans:D
62) If the gain of a critically damped system is increased, it will become
A) Under damped system
B) Over damped system
C) Oscillatory system
D) Critically damped system
Ans:A
63) The frequency domain and time domain are related through
A) Laplace transform
B) Gauss elimination
C) Both (A) and (B)
D) None of the above
Ans:A
64) A system with characteristic equation s^4+2s^3+11s^2+18s+18=0 will have closed loop poles such that
A) All poles lie in the left half of the s-plane
B) All poles lie in the right half of the s-plane
C) Two poles lie symmetrically on the imaginary axis of the s-plane
D) No poles lies on the imaginary axis of the s-plane.
Ans:C
65) If the gain of an open loop system is doubled, the gain margin
A) Is not affected
B) Gets double
C) Becomes half
D) Becomes one-fourth
Ans:C
66) An all pass network imparts only
A) Negative phase to the input
B) Positive phase to the input
C) +/- 90 degree phase shift to the input
D) +/- 180 degree phase shift to the input
Ans:D
67) Which of the following devices are required to measure three phase balanced power?
A) One watt meter
B) One watt meter and one voltage transformer of 1:1 ratio
C) One watt meter and two voltmeter
D) None of the above
Ans:B
68) The sensitivity of an instrument is
A) The smallest increment in the input that can be detected with certainty
B) The largest input change to which the instrument fails to respond
C) Ratio of the change in the magnitude of the output to the corresponding change in the magnitude of the input
D) Closeness of the output values for repeated application of a constant input.
Ans:C
69) Potentiometer sensitivity can be increased by
A) Decrease current in the potentiometer wire
B) Increasing the length of the potentiometer wire
C) Decreasing the length of the potentiometer wire
D) Replacing the cell by a regulated power supply
Ans:B
70) Low resistance is measured with
A) De Sauty's bridge
B) Maxwell's bridge
C) Kelvin's double bridge
D) wien bridge
Ans:C
71) Which bridge is used to determine frequency?
A) Anderson bridge
B) De sautys bridge
C) Wien bridge
D) Campell's bridge
Ans:C
72) The operational amplifier are seldom used for differentiation because
A) Of the problem of drift with differentiating circuits
B) Because of the poor efficiency
C) Because of the complex circuitry requirements
D) The noises are amplified and this can be significant in the output
Ans:D
73) Which of the following multivibrator is called the flipflop ?
A) Astable multivibrator
B) Monostable multivibrator
C) Bistable multivibrator
D) Both (B) and (C)
Ans:C
74) The amount of feedback applied to an amplifier reduces the gain by a factor of 10. The bandwidth
A) Decrease by a factor of 10
B) Increase by a factor of 10
C) Remains the same
D) None of the above
Ans:B
75) In a negative feedback amplifier, the output impedence is decreased
A) If the signal sampled is a voltage
B) If the signal sampled is a current
C) If the feedback signal is a voltage
D) If the feedback signal is a current
Ans:A
76) The ROM consists of
A) A decoder followed by an encoder
B) An encoder followed by an decoder
C) A multiplexer followed by a decoder
D) A multivibrator
Ans:A
77) What are the eign values of the following 2x2 matrix 2 -1 ?
-4 5
A) -1 and 1
B) 1 and 6
C) 2 and 5
D) 4 and -1
Ans:B
78) ∬sin(x+y)dxdy with both limits 0 to Ï€/2
A) 0
B) π
C) π/2
D) 2
Ans:D
79) In the Taylor series expansion of e^x+sinx about the point x=Ï€, the coefficient
A) e^Ï€
B) 0.5 e^Ï€
C) e^(Ï€+1)
D) e^(Ï€-1)
Ans:B
80) A deck of five cards (each carrying a distinct number from 1 to 5) is shuffled thoroughly. Two cards are then removed from the deck, one at a time. What is the probability that the two cards are selected with the number of the first card being one higher than the number on the second card?
A) 1/5
B) 4/25
C) 1/4
D) 2/5
Ans:D
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1) The starting torque of three phase induction motor can be increased by
A) Increasing rotor reactance
B) Increasing rotor resistance
C) Increasing stator resistance
D) None of the above
Ans:B
2) The capacitor start capacitor run single phase induction motor is operationally a
A) Single phase motor
B) Two phase motor
C) Three phase motor
D) A.C Series motor
Ans:B
3) What would happen if the field of a D.C shunt motor is opened?
A) Speed will be reduced
B) Continue to run normally
C) Speed will enormously increase damaging the motor
D) None of the above
Ans:C
4) Equalizer rings in D.C generator with lap windings are used for
A) Equal distribution of current at brush for sparkless commutation
B) prevention of harmonics
C) Reduction of noise and vibration
D) Avoiding overhang
Ans:A
5) The Buchholz relay is normally used to protect the
A) Alternator against all internal faults
B) Oil immersed transformers against all internal faults
C) Synchronous motors against all internal faults
D) Transmission lines against all short circuit faults
Ans:B
6) A 400/200 volts transformer has pu impedence of 0.05. The HV side voltage required to circulate full load current during short circuit test is
A) 20 V
B) 40 V
C) 10 V
D) 5 V
Ans:A
7) Non-loading heat run test on transformer is performed by means of
A) SC test
B) OC test
C) core balance test
D) sumpner's test
Ans:D
8) A three phase induction motor is driving full load torque which is independent of speed. If the lines voltage drops to 90% of rated value, % increase in motor copper losses
A) 23%
B) -18%
C) 123%
D) None of these
Ans:A
9) A synchronous generator is feeding power to infinite bus bars at unity power factor. Its excitation is now increased. It will feed
A) The same power but at a leading power factor
B) The same power but at a lagging power factor
C) More power at unity power factor
D) Less power at unity power factor
Ans:B
10) The steam input into a turbo generator connected to infinite bus is increased. which of the events will take place?
A) The generator will feed more leading KVAR to bus bar and power angle will not change.
B) The generator will feed more real power to bus bar and power angle will increase.
C) The generator will feed more power to bus bar and power angle will decrease.
D) The generator will feed more lagging KVAR to bus bar and power angle will not change.
Ans:B
11) Copper behaves as a
A) Conductor always
B) Conductor or dielectric depending on field strength
C) Conductor or dielectric depending on frequency
D) Conductor or dielectric depending on the electric current density
Ans:A
12) Assuming constant transmission efficiency, if voltage is increased 'n' times, the size of the conductor would be
A) Reduced to 1/n^2 that of the original
B) Increased to n^2 that of the original
C) Reduced to 1/n that of the original
D) Increased to n times that of the original
Ans:A
13) Shunt conductance in overhead power transmission lines is primarily due to
A) Leakage over the insulators
B) Leakage over the conductors
C) Leakage over the poles
D) Leakage between ground and conductors
Ans:A
14) The dielectric strength of SF6 gas (used in circuit breakers) is approximately
A) Same as that of air
B) 2 to 3 times more than air
C) 10 to 20 times more than air
D) 2 to 3 times less than air
Ans:B
15) Ferranti effect states that under certain conditions, the sending end voltage is
A) Less than receiving end voltage
B) More than receiving end voltage
C) Equal to receiving end voltage
D) Not having any impact on the receiving end voltage
Ans:A
16) Over fluxing protection is normally recommended for
A) Generator transformers in power stations
B) Auto-transformers in power stations
C) Stations transformers in power stations
D) Distribution transformers
Ans:A
17) In general AC distribution systems, arc interruption in vaccum circuit breakers are designed to function in a time period of
A) One cycle
B) Two to three cycles
C) Within ten cycles
D) None of the above
Ans:A
18) Systems for Protection from negative-sequence current is provided normally for
A) Transformers
B) Generators
C) Transmission lines
D) Motors
Ans:B
19) Bundled conductors are mainly used in high voltage overhead transmission lines to
A) Reduced line loss
B) Reduced harmonics
C) Reduced corona
D) Increase strength
Ans:C
20) Surge impedence of overhead transmission line is normally in the order of
A) 1-5 ohms
B) 20-30 ohms
C) 300-500 ohms
D) 300000-500000 ohms
Ans:C
21) The bode diagram approach is applied to
A) Non-minimum phase network
B) Minimum phase network
C) Any network of a control system
D) None of the above
Ans:B
22) An ON-OFF controller is
A) P controller
B) Integral controller
C) Non-linear controller
D) PID controller
Ans:C
23) The transfer function of a phase lead controller is (1+3Ts)/(1+Ts). The maximum value of phase provided by this controller is
A) 90
B) 60
C) 45
D) 30
Ans:D
24) The thermal time constant is the time
A) To reach the final steady temperature if the initial rate of increase of temperature were maintained constant
B) To reach 63% of final steady temperature
C) To reach 66.66% of final steady temperature
D) To reach half of the final steady temperature
Ans:A
25)Which of the following circuit has no transients?
A) Pure resistive circuit
B) L-C Circuit
C) R-L-C Circuit
D) R-L Circuit
Ans:A
26) A conductor of length 100 cms moves right angles to a magnetic field of flux density of 2 wb/sq.m. with the velocity of 25m/second. The induced emf in the conductor will be
A) 25 Volts
B) 50 Volts
C) 75 Volts
D) 100 Volts
Ans:B
27) The core of a moving iron instrument is made up of permalloy to
A) Increase sensitivity
B) Reduced temperature effect
C) Reduced effect of stray magnetic field
D) Reduced the size of the instrument
Ans:A
28) Accuracy is defined as
A) The measure of consistency of the readings
B) Closeness with which an instrument reading approaches the true value of the quantity being measured
C) The smallest measurable input change
D) The ratio of the input to output
Ans:B
29) If three amplifiers having the same bandwidth are cascaded, the bandwidth of the resulting amplifier will be
A) Better than that of each stage
B) Worse than that of each stage
C) Same as that of each stage
D) None of the above
Ans:B
30) An element is said to have negative resistance when
A) The element has negative tempeature coefficient.
B) The current/voltage curve has negative slope
C) The element has negative specific resistance
D) The current/ voltage curve has a positive slope
Ans:B
31) An ideal rectifier should have transformer utilization factor (TUF) of 1. If the actual TUF is 3.5, it shows that
A) Diode is under-loaded
B) The transformer must be 3.5 times larger
C) The transformer should be only 1/3.5 times the ideal size
D) The ripple factor is low
Ans:B
32) A power MOSFET is a
A) Voltage controlled device
B) Current controlled device
C) frequency controlled device
D) None of the above
Ans:A
33) When transistors are used in series or parallel, a snubber circuit is used to
A) Control the current
B) Control the voltage
C) Limit di/dt
D) All of these
Ans:C
34)
is equal to
A) -∞
B) 0
C) 1
D) ∞
Ans:C
35) A fair (unbiased) coin was tossed four times in succession and resulted in the following outcomes: (i) Head (ii) Head (iii) Head (iv) Head. The probability of getting a "Tail" when the coin is tossed again is
A) 0
B) 1/2
C) 4/5
D) 1/5
Ans:B
36) Using trapezoidal rule for the table given below ∫lnx dx with limits 5.2 to 4 will be
x : 4 4.2 4.4 4.6 4.8 5.0 5.2
lnx: 1.39 1.44 1.48 1.53 1.57 1.61 1.65
A) 1.8277
B) 1.9284
C) 1.6424
D) 0.98795
Ans:A
37) Find the z transform of (n+1)^2
A) z^2(2z+1)/(z-1)^3
B) (2z+1)/(z-1)^3
C) (2+z)/(z-1)^2
D) (3z+2)/(z-1)
Ans:A
38) Consider the following system of euations in three real variables x1,x2 and x3
2x1-x2+3x3=1
3x1-2x2+5x3=2
-x1-4x2+x3=3
The system of equations has
A) No solutions
B) A unique solution
C) More than one but a finite number of solutions
D) An infinite number of solutions
Ans:B
39) Which of the following functions would have only odd powers of x in its Taylors series expansion about the point x=0?
A) sin(x^3)
B) sin(x^2)
C) cos(x^3)
D) cos(x^2)
Ans:A
40) An inductance of one H carying a current of two amperes will store the energy of
A) 2 watts
B) 2 joules
C) 4 watts
D) 4 joules
Ans:B
41) The square waveform of current has following relation between r.m.s value and average value
A) r.m.s value of current is greater than the average value
B) r.m.s value of current is less than the average value
C) r.m.s value of current is equal to the average value
D) There is no definite relation between the r.m.s value and average value for a square wave
Ans:C
42) Two numbers of 500 ohms one watt resistors are connected in parallel. Their combined resistance and wattage rating will be
A) 250 ohms, 1 watt
B) 250 ohms, 2 watts
C) 1000 ohms, 2 watts
D) 500 ohms, 2 watts
Ans:B
43) In a long uniform coil of inductance 2L and associated resistance 2R ohms is physically cut in to two exact halves which are rewound in parallel. The resistance and inductance of the combination are
A) R and L
B) 2R and 2L
C) R/2 and L/2
D) R/4 and L/4
Ans:C
44) For transfer function of a physical two-port network
A) All zeros must lie only in the left half of the s-plane
B) All poles may lie anywhere in the s-plane
C) The poles lying on the imaginary axis must be simple
D) All the above
Ans:D
45) The power transformer is a
A) Constant current device
B) Constant voltage device
C) Constant frequency device
D) Pulsating main flux device
Ans:D
46) A change of 5% in supply voltage to an induction motor will produce a change of approximately
A) 5% in the rotor torque
B) 7.5% in the rotor torque
C) 10% in the rotor torque
D) 25% in the rotor torque
Ans:D
47) If the supply frequency to the transformer is increased, the iron loss
A) will increase
B) will decrease
C) will not change
D) may reach zero
Ans:A
48) The maximum temperature permitted for class A insulation is
A) 180 degree centigrade
B) 105 degree centigrade
C) 120 degree centigrade
D) None of the above
Ans:B
49) Two transformers connected in parallel share load in the ratio of their KVA ratings, provided their ohmic impedence are
A) Equal
B) In direct ratio of their ratings
C) In inverse ratio of their ratings
D) Purely reactive
Ans:C
50) The high frequency hum in the transformer is mainly due to
A) Loose laminations
B) Magnetostriction
C) Impurity in oil
D) Weakness of tank wall
Ans:B
51) In an ideal transformer, which of the following statement is correct?
A) no voltage drops in resistance or leakage reactance
B) mmf required to maintain main flux is small
C) no core loss
D) all the above are correct
Ans:D
52) The voltage applied to a transformer primary is increased keeping v/f fixed. How will core loss and magnetising current change
A) Core loss will increase and magnetizing current remain same
B) Core loss will remain same and magnetizing current will remain same
C) Core loss will decrease and magnetizing current will increase
D) Core loss will remain same and magnetizing current will decrease
Ans:A
53) Frequency in the UHF range normally propagate by means of
A) Ground waves
B) Sky waves
C) Surface waves
D) Space waves
Ans:D
54) Indicate the antenna that is not wideband
A) Discone
B) Folded dipole
C) Helical
D) Marconi
Ans:D
55) The depth of penetration of a wave in a lossy dielectric increases with increasing
A) Conductivity
B) Permeability
C) Wavelength
D) Permittivity
Ans:C
56) The equal area criterion of stability is applicable to
A) Two machine system and infinite bus bars
B) One machine system and infinite bus bars
C) Multi-machine system only
D) None of the above
Ans:B
57) The power transmisssion capacity of the transmission line is
A) Inversely proportional to the square of the voltage
B) Proportional to the voltage
C) Inversely proportional to the voltage
D) Proportional to the square of the operating voltage
Ans:D
58) If the torque angle 'delta' increases indefinitely, the system indicates
A) Steady state stability
B) Permanent stability
C) Instability
D) None of the above
Ans:C
59) Resistance switching is normally employed in
A) All breakers
B) Bulk oil breaker
C) Minimum oil breaker
D) Air-blast circuit breaker
Ans:D
60) Series capacitors are used to
A) Improve line frequency and eliminate harmonics
B) Compensation for line inductance reactance
C) Neutralise line capacitive reactance
D) None of the above
Ans:B
61) Which of the following methods is the strongest tool to determine the stability and the transient response of the system?
A) Routh-Hurwitz criterion
B) Bode plot
C) Nyquist plot
D) Root locus
Ans:D
62) If the gain of a critically damped system is increased, it will become
A) Under damped system
B) Over damped system
C) Oscillatory system
D) Critically damped system
Ans:A
63) The frequency domain and time domain are related through
A) Laplace transform
B) Gauss elimination
C) Both (A) and (B)
D) None of the above
Ans:A
64) A system with characteristic equation s^4+2s^3+11s^2+18s+18=0 will have closed loop poles such that
A) All poles lie in the left half of the s-plane
B) All poles lie in the right half of the s-plane
C) Two poles lie symmetrically on the imaginary axis of the s-plane
D) No poles lies on the imaginary axis of the s-plane.
Ans:C
65) If the gain of an open loop system is doubled, the gain margin
A) Is not affected
B) Gets double
C) Becomes half
D) Becomes one-fourth
Ans:C
66) An all pass network imparts only
A) Negative phase to the input
B) Positive phase to the input
C) +/- 90 degree phase shift to the input
D) +/- 180 degree phase shift to the input
Ans:D
67) Which of the following devices are required to measure three phase balanced power?
A) One watt meter
B) One watt meter and one voltage transformer of 1:1 ratio
C) One watt meter and two voltmeter
D) None of the above
Ans:B
68) The sensitivity of an instrument is
A) The smallest increment in the input that can be detected with certainty
B) The largest input change to which the instrument fails to respond
C) Ratio of the change in the magnitude of the output to the corresponding change in the magnitude of the input
D) Closeness of the output values for repeated application of a constant input.
Ans:C
69) Potentiometer sensitivity can be increased by
A) Decrease current in the potentiometer wire
B) Increasing the length of the potentiometer wire
C) Decreasing the length of the potentiometer wire
D) Replacing the cell by a regulated power supply
Ans:B
70) Low resistance is measured with
A) De Sauty's bridge
B) Maxwell's bridge
C) Kelvin's double bridge
D) wien bridge
Ans:C
71) Which bridge is used to determine frequency?
A) Anderson bridge
B) De sautys bridge
C) Wien bridge
D) Campell's bridge
Ans:C
72) The operational amplifier are seldom used for differentiation because
A) Of the problem of drift with differentiating circuits
B) Because of the poor efficiency
C) Because of the complex circuitry requirements
D) The noises are amplified and this can be significant in the output
Ans:D
73) Which of the following multivibrator is called the flipflop ?
A) Astable multivibrator
B) Monostable multivibrator
C) Bistable multivibrator
D) Both (B) and (C)
Ans:C
74) The amount of feedback applied to an amplifier reduces the gain by a factor of 10. The bandwidth
A) Decrease by a factor of 10
B) Increase by a factor of 10
C) Remains the same
D) None of the above
Ans:B
75) In a negative feedback amplifier, the output impedence is decreased
A) If the signal sampled is a voltage
B) If the signal sampled is a current
C) If the feedback signal is a voltage
D) If the feedback signal is a current
Ans:A
76) The ROM consists of
A) A decoder followed by an encoder
B) An encoder followed by an decoder
C) A multiplexer followed by a decoder
D) A multivibrator
Ans:A
77) What are the eign values of the following 2x2 matrix 2 -1 ?
-4 5
A) -1 and 1
B) 1 and 6
C) 2 and 5
D) 4 and -1
Ans:B
78) ∬sin(x+y)dxdy with both limits 0 to Ï€/2
A) 0
B) π
C) π/2
D) 2
Ans:D
79) In the Taylor series expansion of e^x+sinx about the point x=Ï€, the coefficient
A) e^Ï€
B) 0.5 e^Ï€
C) e^(Ï€+1)
D) e^(Ï€-1)
Ans:B
80) A deck of five cards (each carrying a distinct number from 1 to 5) is shuffled thoroughly. Two cards are then removed from the deck, one at a time. What is the probability that the two cards are selected with the number of the first card being one higher than the number on the second card?
A) 1/5
B) 4/25
C) 1/4
D) 2/5
Ans:D
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2 comments
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ReplySir, I think in question 47, if the frequency increases then the value of the iron losses will be decreases because the iron losses is directly proportional to the frequency only when the flux is constant(V/f constant) but here only frequency is increases.
ReplySo eddy current losses is constant and hysteresis losses will decreases.
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