B. Triac C. IGBT D. BJT List II A B C D a. 1 2 3 4 b. 1 2 4 3 c. 2 1 3 4 d. 2 1 4 3
41. Natural commutation of a thyristor takes place when
a. Anode current becomes zero b. Gate current becomes zero
c. Voltage across the device becomes zero
d. Voltage across the device becomes negative
42. A gate-turn-off (GTO) thyristor
a. Requires a special turn-off circuit like a thyristor
b. Can be turned off by removing the gate pulse
c. Can be turned off by a negative current pulse at the gate
d. Can be turned off by a positive current pulse at the gate
43. The SCR circuit is shown in the given figure. Which one of the following wave forms represent ‘VT’ when input voltage v is sinusoidal?
44. For a step-down chopper, V1 is the source voltage, ‘R’ is the load resistance and is the duty cycle. RMS and average values of thyristor currents for this chopper are, respectively a. Vs and Vs R R b. Vs and Vs R R c. Vs and Vs R R d. Vs and Vs R R
45. A step - up chopper is required to deliver a load voltage of 660 V from 220 V dc source. If the non -conduction time of SCR is 100 is, the required pulse-width will be a. 300 s
b. 250 s
c. 200 s d. 150 s
46. In a 3-phase half-wave diode rectifier, the ratio of average output voltage to per- phase maximum ac voltage is
a. 0.955 b. 0.827 c. 1.654 d. 1.169
47. Figure 1 shows a 3-phase invertors fed by a constant voltage source VDC and connected to a balanced resistive load at the output. Each switching device may conduct for 1200° or for 180°. The wave form shown in the Figure Ills the
a. Line voltage with 120° firing b. Load phase voltage with 120° firing c. Line voltage with 180° firing d. Load phase voltage with 180° firing 48. The given figure shows electric power
input Pe to a a lossless synchronous motor as a function of torque angle . The load is suddenly increased form P0 to Ps and the motor oscillates around s between 0 and m.
Consider the following statements derived from the figure regarding the relationship between the motor speed and its synchronous speed s at different points in the oscillating cycle:
(i) At point 1, = s
(ii) At point 2, while oscillating from 1 towards 3, <s
(iii)At point 2, while oscillating from 3 towards 1,>s
Which of these statements (s) is/are correct?
a. ii and iv b. i,ii and iv c. i and iii d. Iii alone
49. The reactance of a generator designated X” is given as 0.25 Pu based on the generator’s name plate rating of 18 kV, 500 MVA. If the base for calculations is changed to 20 kV, 100 MVA, the generator reactance X on new base will be a. 1.025 Pu
b. 0.05 Pu c. 0.0405 pu d. 025 pu
50. Consider the following statements:
The calculations performed using short - line approximate model instead of nominal
it model for a medium length transmission line delivering lagging load at a given receiving - end voltage always result in higher
1. Sending - end current 2. Sending - end power 3. Regulation
4. Efficiency
Which of these statements are correct? a. 1 and 2
b. 3 and 4 c. 1, 2 and 3 d. 1, 2 and 4
51. The severity of line to ground and three- phase faults at the terminals of an unloaded synchronous generator is to be same. If the terminal voltage is 1.0 pu, Z1 = Z2 = j 0.1 Pu and Z0 = j 0.05 pu for the alternator, then the required inductive reactance for neutral grounding is
a. 0.0166 pu b. 0.05 pu c. 0.1 pu d. 0.15 pu
52. The surge impedance loading of a long transmission line can be increased without adversely affecting its stability by connecting
a. Lumped inductances in series with the line
b. Lumped inductances in shunt with the line
c. Lumped capacitances in shunt with the line
d. Lumped capacitances in series with the line
53. A transmission line has equal voltages at the two ends, maintained constant by two sources. A third source is to be provided to maintain constant voltage (equal to the end voltages) at either the mid-point of the line (case 1) or at 75% of the distance from the sending end (case 2). Then the maximum power-transfer capabilities of the line in the original case, case 1 and case 2 respectively, will be in the ratio of
a. 1:1:1 b. 1:2:1/0.75 c. 1:2:4 d. 1:4:16
54. A short length of cable is connected between dead-end tower and sub-station at the end of a transmission line. Which of the following will decrease, when voltage wave is entering from overhead line to cable?
1. Velocity of propagation of voltage wave.
2. Steepness of voltage wave. 3. Magnitude of voltage wave.
Select the correct answer using the codes given below
a. 1 and 2 b. 2 and 3 c. 3 and 1 d. 1, 2 and 3
55. The corona contributes a rd harmonic to the charging current of the line, because it a. Occurs every half cycle of the
fundamental frequency
b. Induces a 3rd harmonic voltage between line and earth
c. Produces random harmonics, but only 3rd harmonic is passed through the line capacitance
d. Affects the system grounding for which a 3rd harmonic voltage appears on the line, and causes 3rd harmonic charging current
56. A single line diagram of a power system is shown in the given figure. The diagonal elements of the YBUS matrix is
a. j 0.7 pu, j 0.75 pu, j 0.45 Pu b. – j 0.7 pu, – j 0.75 p – j 0.45 pu c. – j 7.0 pu, – j 6.0 pu, – j 9.0 Pu d. j 7.0 pu, — j 6.0 pu, j 9.0 pu
57. In load - flow analysis, the load at a bus is represented as
a. A constant current drawn from the bus b. A constant impedance connected at the
bus
c. Constant real and reactive powers drawn from the bus
d. A voltage - dependent impedance at the bus
58. Match List I (Relay) with List II (Equipment) and select the correct answer:
List I
A. Mho Relay
B. Negative Sequence Relay C. Thermal Relay. List II 1. Bus bar 2. Motor 3. Generator 4. Transmission line A B C a. 1 3 2 b. 2 4 1 c. 4 2 3 d. 4 3 2
59. Shunt resistor is connected across the contacts of a circuit-breaker in order to a. Damp out the restricting transient b. Bypass the arc current
c. Limit the short-circuit current
d. Reduce the damage to the contacts due to arcing
60. Phase comparison relaying is
a. Used for providing back-up protection to transmission lines
b. Immune to the effects of power surges c. Adversely affected by the currents
flowing in the protected line due to mutual induction from another nearby circuit
d. Adversely affected by the loss of synchronism between sources of generation beyond the ends of the protected line
61. Maloperation of differential protection of transformers due to magnetizing inrush current is prevented by
a. Setting the current of the relay higher than the maximum value of inrush current
b. Keeping the time-setting long enough for the inrush current to fall to a value below the primary operating current of the relay
c. Bypassing the inrush current from the operating coil of the relay
d. Filtering the third harmonic content of the inrush current flowing through the operating coil and passing through the restraining coil
62. Incremental fuel costs in Rs / MWh for a plant consisting pf two units are given by dF1 / dP1 = 0.4P1+400 and dF2/dP2=0.48 P2+320. The allocation of loads P1 and P2 between the units 1 and 2, respectively, for minimum cost of generation for a total load of 900 MW is
a. 200 MW and 700 MW b. 300 MW and 600 MW c. 400 MW and 500 MW d. 500 MW and 400 MW
63. Given figure shows an electromagnet to lift a load of W gram. Assume infinite permeability for iron. The ampere turns of the exciting coil to maintain an equilibrium at an air-gap of x mm would be given by a. 0.874Wx A b. 0.282Wx A c. 8.74Wx A d. 2.82Wx A
64. The series winding of a cumulatively compounded dc motor is short -circuited while driving a load at rated torque. This results in
a. Reduction in both the armature current and the motor speed
b. Increase in the armature current and reduction in the motor speed
c. Increase in- both the armature current as well as the motor speed
d. Reduction in the armature current and increase in the motor speed
65. Consider the following statements regarding an electrical machine having cylindrical stator and salient-pole rotor:
1. Reluctance torque is produced when rotor winding is excited.
2. Reluctance torque is produced when stator winding is excited.
3. When both stator and rotor windings are excited, electromagnetic torque is produced.
4. When both stator and rotor windings are excited, electromagnetic as well as reluctance torques are produced. Which of these statements are correct? a. 2 and 4
b. 1 and 4 c. 1 and 3 d. 2 and 3
66. The identical synchronous machines A and B, running at the same speed, are linked through inductors as shown in the given figure:
Machine A will supply active and reactive power to machine B when is
a. Positive and VA is less than VB b. Positive and VA is greater than VB c. Negative and VA is less than VB d. Negative and VA is greater than VB 67. The given figure shows the equivalent
circuit of a 3-phase induction motor with deep-bar rotor. The sequence of the magnitudes of the parameters of resistances and reactance’s in the ascending order is
a. R R X X R X s, r, / 'r / 'r c' m b. X X R X R / 's / 'r s' m' c c. R R X X R X r' s' / 's / 'r c' m d. R R X X X R s' r' / 's / 'r m' c
68. Which one of the following statements for a dc machine which is provided with inter pole windings (IW) as well as compensating winding (CW) is correct?
a. Both IW and CW are connected in series with the armoire winding,
b. Both IW and CW are connected in parallel with the armature winding c. IW is connected in series but CW is
connected in parallel with the armature winding
d. IW is connected in parallel but CW is connected in series with the armature winding
69. A 3-phase 20-pole, synchronous generator has 180 stator slots with single-layer full pitch coils. There are 6 conductors per slot and all coils per phase are connected in series. The rotor is driven at 300 rpm and the flux per pole (sinusoid ally distributed) is 25 mWb. The voltage induced per phase is nearest to
a. 500 V b. 1000 V c. 1500 V d. 2000 V
70. The Zero Power Factor Characteristic (ZPFC), along with the Open - Circuit Characteristic (0CC) as shown in the given figure are used to determine the Leakage Reactance Drop IaXI at the rated current Ia from the “Potier Triangle” ABC.
In this triangle, BC represents the Isxi (=Vx) drop, because
a. Vx is induced by the mmf AB b. VX is induced by the mmf BD c. VX is induced by the mmf OF
d. VX and the air-gap voltage Er are 180° out of phase at zero p.f. load
71. To calculate the full - load voltage regulation of a synchronous generator at any power factor using mmf method, it is required to have
a. Open-circuit and short - circuit characteristics
b. Open - circuit and zero power factor characteristics
c. Open - circuit characteristics, field current at rated short- circuit current and armature resistance
d. Short - circuit characteristics, zero power factor characteristics and armature resistance
72. Match List I with List II and select the correct answer:
List I (Motors)
A. 1 -phase induction motor B. Steppe motor
C. Universal motor D. Brushless dc motor
List II (Applications)
1. Fast- acting servo drive 2. Hand drilling machine 3. Computer numerical control 4. Domestic pump A B C D a. 3 4 1 2 b. 3 4 2 1 c. 4 3 1 2 d. 4 3 2 1
73. In a 3-phase induction motor, the rotor impedance angle at standstill is . The load angle will be
a. b. c. / 2 d. / 2
74. In the slew range of a stepper motor, it a. Can start, stop and reverse as desired b. Cannot start but can stop and reverse
on command
c. Cannot start, stop and reverse on command
d. Cannot start and synchronize but can reverse on command
75. A 3-phase induction motor develops a torque T when driven from a balanced 3- phase supply. The terminal voltage and frequency are halved so that the air-gap flux remains the same while the load torque is kept constant. Then the slip
a. Is reduced to half
b. Remains same as the previous value c. Speed is reduced to half
d. Speed remains the same 76. Consider the following statements:
A ceiling fan fails to start because 1. Main winding is open-circuited.
2. Auxiliary winding is open-circuited. 3. Capacitor is short-circuited.
4. Supply terminals are reversed.
5. Main and auxiliary winding connections are interchanged.
Which of these statements are correct? a. 1, 2 and 5
b. 2, 3, 4 and 5 c. 1, 2 and 3 d. 1, 3 and 4
77. Hysteretic loss of a transformer designed at voltage ‘V’ and frequency ‘f’ is Ph. If the transformer is operated from a voltage xV’ and frequency ‘xf’ the hysteretic loss for a Steinmetz constant of 2 will be a. X2Ph
b. XPh c. Ph d. X3Ph
78. Which one of the following figures represents the correct direction of flow of currents in the different sections of the windings of an auto transformer?
79. Assertion (A): The driving point
admittance function of a passive network cannot have multiple poles on the j - axis.
Reason (R) : Multiple poles on the j - axis give rise to time domain functions of the type t cos t and t sin t.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
80. Assertion (A): If the voltages across R. L
and C elements connected in series in an ac circuit are 300 V, 100 V and 500 V respectively, then the total voltage applied will be 500 V.
Reason (R): The applied voltage in LCR
series circuit is equal to the maximum
voltage existing across any of these elements.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
81. Assertion (A): Hardware stack registers
speed up the operation of computer..
Reason (R): Hardware stack registers
reduce the number of memory references required.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
82. Assertion (A): ECL gate has less
propagation delay as compared to TTL and CMOS gates.
Reason (R): ECL gate consumes less
power.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
83. Assertion (A): The individual active and
passive components in IC should be electrically isolated from one another before metallization.
Reason (R): The epitomical layer in
which these components are fabricated can provide a common leakage path.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
84. Assertion (A): A low voltage standing
wave ratio (VSWR) is the goal in a transmission line.
Reason (R): The higher the VSWR the
greater is the mismatch on the line.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
85. Assertion (A): Square law detectors,
though simple, are not satisfactory for the detection of amplitude modulated signals.
Reason (R): Square law detection leads to
large second harmonic distortion, which is proportional to the modulation index of the sinusoidal signal.
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is NOT the correct explanation of A
c. A is true but R is false d. A is false but R is true
86. For network shown in the given figure, the current in the 2 resistor would be
a. 5 A b. 20A c. 25A d. 30A
87. In the given circuit, if the inductor is initially relaxed, then the current in the circuit will be a. Zero b. L R/
t c. 1e Rt L L d. 1 1 e Rt L L 88. In a two-port network, the output short- circuit current was measured while the source voltage at the input was 1 V; the value of the output current would provide the parameter
a. B b. y12
c. y21 d. h21
89. An RC driving point impedance function has zeros at s = – 2 and s = – 5. The admissible poles for the function are
a. S = 0 and s= –6 b. S = – l and s = –3 c. S = 0 and s –1 d. S = –3 and s = –4
90. For the circuit shown in the given figure, the switch ‘K’ was closed for a long time till steady state conditions reached. At time t = 0, the switch ‘K’ is opened, then the current through inductor will be
a. 5 cos 10t b. 5 cos 100t c. 5 cos 1000t d. 5 cos 10000t
91. For the circuit shown in the given figure, steady state is reached with switch ‘S open. At t = 0, when switch S is closed, then the values of v (in V) and dv/dt (in V/s) respectively at t = 0+ will be
a. 1 and 0 b. 2 and 1 c. 2 and 0 d. 1 and 1
92. Input impedance of a CR0 measured at 10 kHz is Z1 and at 10 MHz is Z2. Which one of the following relations is correct? a. |Z1| | Z2|
b. |Z1| | Z2| c. |Z1| | Z2| d. |Z1| 1000 | Z2|
93. The quality factor of a series circuit consisting of 20 resistance, 0.05 H inductance and 1 F capacitance is
a. 20.15 b. 11.2 c. 8.7 d. 4.5
94. The voltage v0 for the circuit shown in the given figure will be
a. 1 1 s M V L b. 1 1 s M V L c. 1 1 s M V L d. 2 1 s M V L
95. The dc component of the function it sin t is a. 0
b. 1 c. 2 d. 2 /
96. Consider the following statements:
If the differential equation for the circuit shown in the given figure is v(t) = – 4 v(t) + 4. Then the set of values of E, R and C are, respectively
1. 1V,1 and 0.25 F 2. 2V.0.5 and 0.5F 3. 2 V. 1 and 0.5 F. 4. 1 V.0.25 and 1 F.
Which of these statements are correct? a. 1 and 2 b. 2 and 3 c. 3 and 4 d. 1 and 4 97. If X(z) = Z transform of x(n), then a. X
1 x
0 b. X
1
x n
c. X
1 x
0 d. X
1
x n
98. The function x(t) is shown in the given figure. If X
j is the fourier transform of the x(t), then |X j
|
at = 0 will bea. 0.5 b. 1.5 c. 2 d. 3
99. The function
2n is equal to a.
nb. 1 / 2
n c. 2
n d. 2
n/ 2
100. A band pass signal having the frequency contents in the range of 1 MHz to 2 MHz is to be sampled. The original signal can be reconstructed, if the minimum sampling rate is
a. 106 samples/s b. 2 ×106 samples/s c. 4 × 106 samples/s d. 6 × 106 samples/s
101. For the feedback system shown in the given figure, the forward path does not affect the system output when KG is
a. Small b. Negative c. One d. Very large
102. If a system has an open loop transfer function 1
1 s s
then the gain of the system at frequency at 1 rad/s will be
a. 1 b. ½ c. Zero
d. -1
103. A system block diagram is shown in the given figure. The overall transfer function of the system is
The value of ‘X’ would b e equal a. H3
b. G1H3 c. G2H3 d. G3H3
104. The signal flow graph of the system is shown in the given figure. The transfer function C(s) / D(s) of the system is
a.
1 2 1 2 1 G s G s G s G s H s b.
1 2 1 2 1 G s G s G s G s H s c.
2 1 2 1 G s G s G s H s d.
2 1 2 1 G s G s G s H s 105. The response of a system to a unit ramp input is ½ t-1/8 u(t)+1/8e-4t. Which one of the following is the unit impulse response of the system?
a. 1e4t
b. 2 1
e4t
c. e4td. 2e4t
106. If a second order system has poles at —1 ± j, then step response of the system will exhibit a peak value at
a. 4.5 s b. 3.5 s
c. 3.14 s d. 1 s
107. The gain margin of a unity negative feedback system having forward transfer function
1
k s sT is a. Infinity b. kT c. 1 d. Zero108. The impulse response of a linear system is given by g(t) =Ke-t/r A tangent is drawn to the impulse response curve at time t=0. the tangent will intersect the time axis at a. 1 / 2
b. c. 2 d. K
109. A system is shown in the given figure. The value of K which gives a steady - state error of 20% to a unit step - input is given by
a. 500 b. 100 c. 20 d. 4
110. The transfer function for a system is
2
, 0 1 3 4 K s G s K s s s Two branches (loci) of the plot directed along asymptotes are centered at a point a. –3
b. –4 c. –2 d. –1
111. The number of roots in the left-half of s- plane for the equation s3 — 4s2 + s + 6 = 0, would be
a. 1 b. 2 c. 3 d. 4
1. Squirrel-cage or drag-up type rotor.
2. Nearly linear torque -speed characteristics.
3. High X / R ratio.
Which of these features are possessed by a two-phase ac servomotor?
a. 1,2 and 3 b. 1 and 2 c. 2 and 3 d. 1 and 3
113. The current ‘I’ flowing through a resistance of value 100 0.2% is
4A0.5%
The uncertainty in measurement of power is
a. 1600 W ± 0.01% b. 1600 W ± 0.02% c. 1600 W ± 0.05% d. 1600 W ± 1.2%
114. The impedances of a basic ac bridge arms are 250 100 60 400 30 AB BC CD Z A Z DA Z Unknown
If 1000radian/s, the components of the unknown arm has the resistance
500 3 in
a. Series with a capacitor of 2. F b. Parallel with a capacitor of 2 F c. Series with an inductor of 2 H d. Parallel with an inductor of 2 . H 115. In a low power-factor wattmeter.
compensating coil is employed in order to a. Neutralize the capacitance effect of
pressure coil
b. Compensate for the inductance of pressure coil
c. Compensate for the error caused by power loss in the pressure coil
d. Reduce the error caused by the eddy - currents
116. The battery voltage of an analog multimetr drops by 20% of its original value. The
multimeter is used to measure dc voltage in a circuit. The true voltage compared to the measured value is
a. 10% higher b. 20% higher c. 20% lower d. Same
117. Which one of the following causes the disc in an induction type of energy meter to rotate in the opposite direction?
a. The breaking magnet is faulty
b. Both current coil and voltage coil are wrongly connected
c. Either current coil or voltage coil is wrongly connected
d. The load is highly reactive
118. In a semiconductor strain gauge, the