BPSC Exam 2025: Integrated 70th Combined Main (Written) Competitive Examination, Optional, Electrical Engineering
Text of page 1
Serial No.
Booklet Series
02/GO/CC/M-2025 – 12
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Candidate’s Roll Number
Question Booklet
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ELECTRICAL ENGINEERING
Time Allowed : 2 Hours Maximum Marks : 100
Read the following instructions carefully before you begin to answer the questions.
IMPORTANT INSTRUCTIONS
1. This Question Booklet is divided into two Sections. Section – I and Section – II. Section – I is compulsory.
Section – II consists of three Parts. Part – A is compulsory and candidates shall answer questions from any one
Part out of two Parts Part – B or Part – C.
2. This Question Booklet contains 125 questions in all. Section – I consists of Question Nos. 1 to 50 (Compulsory),
Section – II : Part – A consists of Question Nos. 51 to 75 (Compulsory), Section – II : Part – B consists of Question
Nos. 76 to 100 and Section – II : Part – C consists of Question Nos. 101 to 125.
3. Attempt questions from Section – I (Compulsory), Section – II : Part – A (Compulsory) and Section – II : Part – B
OR Section – II : Part – C.
4. All questions carry equal marks.
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SECTION – I
(Compulsory)
1. At a conductor-dieletric boundary, the 4. A sine wave voltage is applied across
a capacitor, when the frequency of the
(A) Along the surface voltage is increased, the current through
the capacitor
(B) Absent
(A) is zero
(C) Normal to the surface
(B) decreases
(D) Zero
(C) remains the same
2. A (0 – 300) V voltmeter has guaranteed
accuracy of 1% full scale reading. The (D) increases
voltage measured by the instrument is
83 V. The percentage limiting error is
5. Multivibrator circuit that remains in stable
(A) 4.85 % state until a triggering signal causes a
transition to quasistable state and returns
(B) 1.81 %
to stable state after certain time is called
(C) 3.61 %
(A) Astable multivibrator
(D) 0.95 %
(B) Bistable multivibrator
(C) Monostable multivibrator
3.
emitter at –2 V and collector at +1 V, (D) None of these
then
6. For successful parallel operation of two
+1V
single phase transformers, the essential
C
0V condition is that their
B
E (A) KVA ratings should be equal
–2V
(B) Turns ratio should be exactly equal
(A) collector is reverse biased
(C) Polarities must be properly
(B) emitter is reverse biased connected
(C) emitter is forward biased (D) Percentage impedances should be
equal
(D) none of these
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7. An integrating digital voltmeter measures 10. 0 sin t, what
(A) Peak to peak value is the phase difference between the
(B) RMS value
conduction current and the displacement
(C) Peak value
current ?
(D) True average value
(A) 180°
8. Maximum starting torque of a 3-phase
(B) 45°
induction motor is obtained when the
(A) rotor resistance is 1.5 times that of (C) 90°
rotor reactance
(D) 0°
(B) rotor resistance is very small and rotor
reactance is large
(C) rotor resistance is double that of the 11.
rotor reactance
of an oscillator. If the voltage gain of the
(D) rotor resistance is equal to the rotor
reactance
what should be the value of feedback
9. What is the peak current through the
fraction ‘m’ to sustain oscillation ?
resistor in the circuit given below assuming
the diode to be ideal ? +
Voltage
V1 V0
Gain A –
1K
12 sin t ~ 4V
mV0 Feedback
Circuit
(A) 0.05
(A) 16 mA
(B) 0.01
(B) 8 mA
(C) 0.1
(C) 12 mA
(D) 4 mA (D) 0.02
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12. Full-load voltage regulation of a power 15.
give
transformer is zero when power factor of
the load is near to (A) larger bandwidth
(A) unity and lagging (B) impedance matching
(B) zero and leading (C) maximum current gain
(D) maximum voltage gain
(C) zero and lagging
(D) unity and leading
16. The armature reaction of a synchronous
generator under short circuit condition is
13. A source of angular frequency 1 rad/s
has a source impedance consisting (A) Both demagnetising and cross
of 1 resistance in series with 1 H magnetising
inductance. The load that will obtain the
(B) Cross magnetising
maximum power transfer is
(C) Demagnetising
(A) 1 resistance in parallel with 1 F
capacitor (D) Magnetising
(B) 1 resistance in parallel with 1 H
17.
inductance
voltage is zero. The switch is closed at
(C) 1 resistance in series with 1 F
capacitor the capacitor is
(D) 1 resistance
10
20 V 20 F 10
14. Improved commutation in D.C. machines
can not be achieved by
(A) decreasing reactance voltage (A) 0 V
(B) using brushes of higher resistivity (B) 10 V
(C) increasing reactance voltage (C) 5 V
(D) use of interpoles
(D) 20 V
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18. Maxwell’s inductance-capacitance bridge 20. Consider the following statements
regarding an RC phase-shift oscillator.
is used for measurement of inductance of
(A) Low and medium Q coils
(B) Medium Q coils only 3. The phase shift introduced by the
feedback network is 180°.
(C) High Q coils only
4. The phase shift introduced by the
feedback network is 360°.
(D) Low Q coils only
Of these statements :
(A) 1 and 4 are correct
19. (B) 2 and 3 are correct
is to be operated with VCC (C) 2 and 4 are correct
RC . The maximum power
(D) 1 and 3 are correct
dissipation of the transistor is
+VCC 21. In A.C. rotating machines, the generated
or speed emf
IC RC
RB by 180°
by 90°
~ by 90°
(A) 0.25 W
22. The Fourier transform of a rectangular
pulse is
(B) 1.5 W
(A) Impulse function
(B) Triangular pulse
(C) 0.1 W
(C) Sinc function
(D) 0.5 W (D) Another rectangular pulse
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23. On switching a D.C. motor is found to 26.
rotate in the direction opposite to that for
(A) a digital to analog converter
which it is designed. The motor is
(B) a sequential circuit
(A) Shunt
(C) an analog to digital converter
(B) Differential compound
(D) a combinational circuit
(C) Series
(D) Cumulative compound
27.
across terminal A and C and the output
24. in , is across B and D. The output is
then current through the Zener diode is B C
R
Vin
Vz Vout
A D
(A) 6.25 mA (B) Same as input
(B) 12.5 mA
(D) Zero
(C) 50 mA
(D) 25 mA
28. A Lissajous pattern on an oscilloscope
has 5 horizontal tangencies and 2 vertical
D
25. The Maxwell’s equation H J is tangencies. The frequency of the
t
based on horizontal input is 1000 Hz. What is the
frequency of the vertical input ?
(A) Faraday’s law
(A) 5000 Hz
(B) Coulomb’s law
(B) 2500 Hz
(C) Gauss’s law (C) 4000 Hz
(D) Ampere’s law (D) 400 Hz
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29. For an RC driving-point impedance 32. The sequential circuits are circuits whose
function, the poles and zeros
output depends upon
(A) can lie anywhere on the left half
(A) the present combination of input and
plane
past output
(B) should alternate only on the negative
real axis (B) on present input only
(C) should alternate on the imaginary (C) on past output only
axis
(D) none of these
(D) should alternate on real axis
30. When the collector junction in transistors 33. In a charge free space, the Poisson’s
is biased in the reverse direction and the
equation results in which one of the
emitter junction in forward directions, the
following ?
transistor is said to be in the
(A) Continuity equation
(A) cut-off region
(B) active region (B) Laplace equation
(C) saturation region (C) Maxwell’s equation
(D) none of these
(D) None of these
31. The precision of a ramp type digital
34. The power transformer is a
voltmeter depends on
(A) switching time of the gate (A) constant power device
(B) frequency of the generator
(C) slope of the ramp
(C) constant current device
(D) frequency of the generator and slope
of the ramp (D) constant voltage device
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35. A Bipolar junction transistor is a 38. If the mechanical load of a 3 phase
(A) Voltage controlled current device induction motor is increased from no
(B) Current controlled voltage device load, then
(C) Voltage controlled voltage device (A) Power factor becomes zero
(D) Current controlled current device (B) Power factor decreases
36. A transient current in a network is (C) Power factor remains constant
–t – e– 5t
plot of I(s) is (D) Power factor increases
j
(A) o x x
–9 –5 –1
x Pole 39. A plane wave is travelling in the positive
o Zero X-direction in a lossless unbounded
j medium having permeability the same as
(B) o x the free space and a permittivity 9 times
–5 –1 2
that of the free space, the phase velocity
j of the wave will be
(C) x o x o
–1 1 2 5
(A) 3 108 m /s
j
(B) 108 m/s
(D) x x o
1 5 9 1
(C) 108 m /s
3
(D) 3 × 108 m/s
37. In a combinational circuit the output
(A) does not depend upon any present or
past input
40. A full adder has
(B) depends upon the present input and
(A) 2 inputs and 2 outputs
past output
(B) 3 inputs and 2 outputs
(C) depends upon the combination of
present input only (C) 3 inputs and 1 output
(D) depends upon the past output
(D) 3 inputs and 3 outputs
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41. The power in a 3 phase circuit is 44. The full-load copper loss and the iron loss
measured with the help of 2 wattmeters.
The reading of one of wattmeter is of a transformer are 6400 W and 5000 W
positive and that of the other is negative.
The magnitude of readings is different. It respectively. The copper loss and iron
can be concluded that the power factor
of the circuit is loss at half of full-load will be respectively
(A) Less than 0.5 (lagging)
(A) 1600 W and 1250 W
(B) Zero (lagging)
(C) 0.5 (lagging)
(B) 1600 W and 5000 W
(D) Unity
(C) 3200 W and 5200 W
42. Which of the following shift register will
require minimum number of clock pulses
(D) 3200 W and 2500 W
to give the output ?
(A) Parallel In Parallel Out (PIPO)
(B) Parallel In Serial Out (PISO)
45.
(C) Serial In Parallel Out (SIPO)
(D) Serial In Serial Out (SISO) has
VCC
RC
43 Which of the following Dirichlet’s
conditions are correct for convergence of RB
Fourier transform of the function x(t) ?
1. x(t) is square integrable. V
RE
2. x(t) must be periodic.
interval. (A) Fixed biasing scheme
(B) No biasing arrangement
interval.
(A) Only 2, 3 and 4 (C) Self-biasing or emitter biasing
(B) Only 1, 2 and 4 scheme
(C) Only 1, 3 and 4
(D) None of these
(D) 1, 2, 3 and 4
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46. 48. 1 and C2 are
of Z is ideal capacitors, C1 has been charged to
12 V before the ideal switch S is closed
A
B
Z
C S
–
(A) A BC C1 C2
i (t)
––
(B) A B C
(A) an impulse function
(C) Zero (B) a step function
(C) an exponentially decaying function
(D) ABC
(D) zero
47. Assume that D1 and D2 49. By increasing the number of stages in an
given below are ideal diodes. The value
of current ‘I’ is
(A) increases
(B) becomes unity
2k
D1 (C) remains constant
(D) goes to zero
1mA
(DC) I
2k 50. An electromagnetic wave is transmitted
D2 into a conducting medium of conductivity .
The depth of penetration is
(A) inversely proportional to square root
(A) 2 mA
of frequency
(B) 0.5 mA (B) directly proportional to square root of
frequency
(C) 1 mA
(C) inversely proportional to frequency
(D) 0 mA (D) directly proportional to frequency
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SECTION – II (Part – A)
(Compulsory)
51. The system with the open loop transfer 54. Ward-Leonard system of speed control is
1 not recommended for
function G(s) H(s) 2
has a
gain margin of s(s s 1) (A) Very low speed
(A) 6 dB (B) Constant speed operation
(B) 0 dB (C) Frequent motor reversal
(C) 3.5 dB (D) Wide speed range
(D) – 6 dB
55. Consider a characteristic equation given
by s4 + 3s3 + 5s2 + 6s + K + 10. The
52. If a separately excited DC motor is to be
condition for stability is
o
converter is used in (A) – 10 < K < – 4
(A) Four quadrant chopper (B) – 10 < K
(C) K > – 4
(C) S i ng le p ha s e d u a l co nt r o l l ed (D) K > 5
56. Th
K (s a )
controller is given as Gc (s)
53. (s b )
Y(s) where K, a and b are positive real
given below. The transfer function numbers. The condition for this controller
U(s)
for this system is to act as a phase lead compensator is
(A) K > ab
(B) a > b
(C) K < ab
(D) a < b
s 1 57. Which one of the following device is
(A) 2 uncontrolled ?
5s 6s 2
s 1 (A) TRIAC
(B) 2
s 4s 2
(B) MOSFET
s 1
(C) (C) Diode
s2 6s 2
(D) None of these (D) SCR
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58. An element that stores kinetic energy of 63. The presence of ac source resistance in
rotational motion is called
(A) Mass
(B) Torsional spring (A) Reduction in output dc voltage
(C) Damper (B) Reduction in the load current ripples
(D) Inertia
(C) Increase in the load current angle
10
59. The polar plot of G(s) intercepts (D) Increase in output dc voltage
s(s 1)2
real axis at 0. Then the real part and
0 are, respectively, given by
(A) – 5, 2 64. The root locus diagram for a closed loop
(B) – 5, 0.5
(C) – 5, 1 The system is overdamped
(D) – 2.5, 1
60. Ideal regulated power supplies have
voltage regulation in percentage as
(A) 5
(B) 7
(C) 0
(D) 2
61. A single phase full bridge inverter has (A) If 0 K < 1 or K > 5
F. The dc input voltage is 230 V (B) Only if 1 < K < 5
and the output frequency is 50 Hz. Find
the rms value of the fundamental load (C) Only if K > 5
current.
(A) 26.90 A (D) Only if 0 K 1
(B) 20.02 A
(C) 16.69 A
65. A unity feedback control system has an
(D) 28.31 A
open loop transfer function a1 2 0,
62. A critically damped, continuous-time, a3 0. If the input to the system is a unit
second order system, when sampled, will ramp, the steady state error will be
have in z-domain
(A) A pair of complex conjugate poles
(B) 0.5
(B) Double pole on real axis
(C) 2
(C) Double pole on imaginary axis
(D) 0
(D) A simple pole
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66. 69. A second order system has a transfer
C( s) function given by x1(t ) 2x1(t ) u( t) . If
is the system, initially at rest, is subjected to
R(s)
in the response will occur at
(A) /2 sec
(B) /3 sec
(C) 2 /3 sec
(D) sec
70. What is the formula for output voltage for
Buck-Boost converter ?
1 (A) D × Vin / (1 + D)
(A)
1 G1G2H1 G3 G4H2 G2G3H3 G1G2 G3G4H1H2
(B) Vin / (1 – D)
G1G2G3 G4 (C) D × Vin / (1 – D)
(B)
1 G1G2H1 G3G4H2 G2G3H3 G1G2G3 G4H1H2
(D) D × Vin
1
(C) 1 G1G2H1 G3G4H2 G2G3H3 G1G2G3 G4H1H2
71. The approximate Bode magnitude plot
of a minimum phase system is shown in
G1G2 G3 G4
(D) 1 G1G2H1 G3G4H2 G2G3H3 G1G2G3G4H1H2 system is
67. A certain pulse measures 10 ms and has
a period of 50 ms. The duty cycle is
(A) 50%
(B) 10%
(C) 20%
(D) 5%
68. Power is delivered to a resistive load
of 50 by a three-phase diode bridge
9 (s 0.1)3
50 Hz ac supply. The peak value of the (A) 10
(s 10)(s 100)2
instantaneous load voltage would be
7 (s 0.1)3
(A) 400 2 / 3 V (B) 10
(s 10)(s 100)
(B) 400 2 V
8 (s 0.1)2
(C) 10
(C) 400 V (s 10)2 (s 100)
8 (s 0.1)3
400 (D) 10
(D) V (s 10)2 (s 100)
3
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72. 74. A chopper is employed to charge a battery
is/are covers the range of very smooth current is 5 A. The duty ratio is 0.2. The
chopper output voltage is also shown in
in the charging current is
(D) All of the above
C(s)
73. The transfer function of the block
R(s)
(A) 1 A
(B) 1.2 A
(C) 2.4 A
(D) 0.48 A
G1
(A)
1 G1 G2
75. A unity feedback control system has an
open-loop transfer function
K
(B) G1G2 + G1 + 1 G(s) . The gain K for
2
s(s 7s 12)
of this system is
(C) G1G2 + G2 + 1
(A) 10
(B) 5.5
G1G2
(D) (C) 6.5
1 G1 G2
(D) 4
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SECTION – II (Part – B)
76. The direct axis and quadrature axis 79. Speed of induction motor
reactances of a salient pole alternator
are 1.2 pu and 1.0 pu respectively. The (A) Decreases slightly with the increase
armature resistance is negligible. If this
of load
alternator is delivering rated kVA at upf and
at rated voltage then its power angle is (B) Remains constant with the increase
(A) 90°
of load
(B) 45°
(C) 60° (C) Decreases too much with the increase
(D) 30°
of load
77. A 220 kV, 20 km long, 3-phase
(D) Increases with the increase of load
transmission line has the
following A, B, C, D constants :
A D 0.96 3 , B 55 65 /phase, 80. A 50 Hz synchronous generator is initially
4
C 0.5 10 90 S/phase. Its correct connected to a long lossless transmission
charging current per phase is line which is open circuited at the receiving
220 the generator is disconnected from the
(A) A
3 transmission line. Which of the following
may be said about the steady state
(B) 11 A
(C) 220 A generator ?
11 (A) The magnitude of terminal voltage
(D) A
3
decreases
78. Under no-load condition, if the applied
voltage to an induction motor is reduced (B) The magnitude of terminal voltage
from the rated voltage to half the rated
value not change
(A) There is negligible change in the speed
but the stator current decreases (C) The magnitude of terminal voltage
(B) Both the speed and the stator current
decreases increases
(C) The speed and the stator current
remain practically constant (D) The magnitude of the terminal voltage
(D) The speed decreases and the stator
current increases not change
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81. A single phase AC distributor supplies 84. Xd, Xd and X d are steady state d-axis
two single phase loads as shown in the
synchronous reactance, transient d-axis
ure. The voltage drop from A to C is
reactance of a synchronous machine
respectively. Which of the following
statements is true ?
(A) X d Xd Xd
(B) X d Xd Xd
(C) X d Xd Xd
(A) 20 V
(D) X d Xd X d
(B) 31.5 V
(C) 30 V
(D) 4.5 V 85. A cylindrical rotor generator delivers 0.5 pu
82. The motor enclosure used for industrial
purpose is through a transmission line of reactance
(A) Drip proof type 0.5 pu. The generator no-load voltage is
(B) Protected type
(C) Open type and drip proof type
The inertia constant of the generator is
(D) Totally enclosed type
5 MW-s/MVA and the generator reactance
is 1 pu. The critical clearing angle, in
83. An induction motor having full load torque
of 60 Nm, when delta connected develops degrees, for a three phase dead short
a starting torque of 120 Nm. For the same
supply voltage, if the motor is changed circuit fault at the generator terminal is
to star connection, the starting torque
developed will be (A) 79.6
(A) 120 Nm
(B) 60.2
(B) 60 Nm
(C) 70.8
(C) 90 Nm
(D) 40 Nm (D) 53.5
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86. The bus impedance matrix of a 4-bus 88. The fuel cost functions of
power system is given by two power plants are, Plant
j0.3435 j0.2860 j0.2723 j0.277 P 1 : C1 0.05 Pg12 APg1 B and
j0.2860 j0.3408 j0.2586 j0.2414 Plant P 2 : C 2 0.10Pg22 3APg2 2B
Zbus
j0.2723 j0.2586 j0.2791 j0.2209 where Pg1 and Pg2 are the generator
j0.2277 j0.2414 j0.2209 j0.2791 . powers of two plants and A and B are the
constants. If two plants optimally share
Branch having an impedance of j0.2 1000 MW load at incremental fuel cost of
is connected between bus 2 and the 100 RS/MWhr, the ratio of load shared
by plants P1 and P2 is
reference. Then the value of Z22, new and
(A) 4 : 1
Z23, new of the bus impedance matrix of
(B) 2 : 3
(C) 3 : 2
(D) 1 : 4
(A) j0.1260 and j0.1630
(B) j0.1260 and j0.0956 89.
(C) j0.5408 and j0.0956
(B) One set of brushes per pole
(D) j0.5408 and j0.4586
quadrature
(D) All of the above
87. A 400V, 50 Hz, 30 hp, 3-phase induction
motor is drawing 50 A current at 0.8 power
factor lagging. The stator and rotor copper 90. A 100 kVA, 415 V star connected
losses are 1.5 kW and 900 W respectively. synchronous machine generates rated
The friction and windage losses are 1050 W
and the core losses are 1200 W. The air current of 15 A. The rated armature
gap power of the motor will be current is 10 A. The per unit saturated
(A) 26.21 kW synchronous reactance is
(A) 0.5777
(B) 24.11 kW
(B) 1.5
(C) 25.01 kW (C) 0.666
(D) 23.06 kW (D) 1.731
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91. A 3-phase induction motor is driving a 93.
constant torque load at rated voltage and zero sequence reactances in pu are
indicated. The zero sequence driving
frequency. If both voltage and frequency point reactance of the node 3 is
are halved, following statements relate
to the new condition if stator resistance,
leakage reactance and core loss are
ignored
i. The difference between synchronous
speed and actual speed remains (A) 0.20
same.
(B) 0.30
(C) 0.10
iii. The stator current remains same.
(D) 0.12
iv. The pu slip remains same.
Among the above correct statements are
94. The armature of a single phase alternator
(A) i and iv is completely wound with T single turn
coils distributed uniformly. The induced
(B) i, ii and iii voltage in each turn is 2 V(rms). The emf
of the whole winding is
(C) ii, iii and iv (A) 1.273 T V
(D) All (B) 1.11 T V
(C) 1.414 T V
(D) 2 T V
92.
(A) To provide current path during positive
95. The plugging provides _________ braking
half cycle
torque in comparison to rheostatic and
(B) To provide current path of discharging regenerative breaking systems.
of capacitor
(A) Negligible
(C) To provide current path during (B) Highest
negative half cycle (C) Small
(D) None of these (D) None of these
02/GO/CC/M-2025 – 12/I -34-
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96. The quantity which make rotating 98. A 400 V, 15 kW, 4 pole, 50 Hz Y-connected
induction motor has full load slip of 4%.
The output torque of the machine at full
is/are
load is
(A) Favourable steady state conditions
(A) 624.73 Nm
(B) Favourable transient conditions (B) 95.50 Nm
(C) High power gain (C) 99.47 Nm
(D) 1.66 Nm
(D) High power gain and favourable
transient conditions
99. The rate of heat produced by dielectric
heating is increased by
97. A 500 MVA, 50 Hz 3-phase turbo generated
(A) Decreasing frequency and increasing
produces power at 22 kV. Generator is voltage supply
Y-connected and its neutral is solidly
(B) Increasing frequency and decreasing
grounded. Its sequence reactances are voltage supply
X1 2 0
(C) Decreasing frequency and voltage
at rated voltage and disconnected from the
supply
rest of the system. The magnitude of the
(D) Increasing frequency and voltage
sub-transient line current for single line to
supply
ground fault at the generator terminal in
pu will be 100. The ordinary dc machines are not
favourable as amplidynes due to
(A) 8.553
(A) High steady state error
(B) 3.333
(B) Low stability
(C) 6.667 (C) Poor gain
(D) 2.851 (D) Sluggish transient response
02/GO/CC/M-2025 – 12/I -36-
Text of page 38
OR
SECTION – II (Part – C)
101. Two dissimilar antennas having their 104. The principle of operation of a Gunn
maximum directivities equal diode is based on
(A) Must have their effective aperture
(A) Carrier recombination
areas also equal
(B) Cannot have their beam widths (B) Negative resistance
equal because they are dissimilar
(C) Tunnelling effect
antennas
(C) May not necessarily have their (D) Avalanche breakdown
maximum power gains equal
(D) Must have their beam widths also
equal 105. A zero mean white Gaussian noise is
102. Any device with negative impedance as
of bandwidth 10 KHz. The output is then
its characteristic property can be called
uniformly sampled with sampling period
(A) Energy source
ts
(B) Oscillator
would be
(C) Energy sink
(D) None of the above (A) Orthogonal
(B) Statistically independent
2 sin 2 t
103. m(t ) , (C) Uncorrelated
t
sin199 t
s( t ) cos 200 t and n(t ) . (D) Correlated
The output y(t) will be t
106. When both input and output of an
the transducer power gain is
2
sin 2 t sin 0.5 t (A) S11
(A) cos 0.75 t
t t
sin 2 t sin t 2
(B) cos 3 t (B) S22
t t
2
sin 2 t sin 0.5 t cos 1.5 t (C) S12
(C)
2t t
2
sin2 t (D) S21
t
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107. Which of the following is a common 110. Magnetron is a
(A) Low power oscillator
(A) Wireless communication CCCCCCCCCCCC
(C) High power oscillator
(B) Signal conditioning in instrumentation CCCCCCCCCCCC
systems
111. What type of microwave tube is typically
(C) Radio frequency transmission
used in radar transmitters ?
(B) Klystron
(C) TWT
108. A 4 GHz carrier is DSC-SC modulated by (D) Magnetron
a low pass message signal with maximum
112. The AM signal gets added to a noise
frequency of 2 MHz. The resultant signal
with power spectral density Sn(f) given
is to be ideally sampled. The minimum he ratio of average
frequency of the sampling impulse train sideband power to mean noise power
should be would be
(A) 8.004 GHz
(B) 8 MHz
(C) 8 GHz
(D) 4 MHz
25
109. In air, a lossless transmission line of length
(A) N B
0
is operated at 25 MHz. Its electrical path
25
length is (B)
4N0B
(A) 180 degrees
25
(B) meters (C)
2N0B
(C) /2 radians
25
(D)
(D) 0.5 meters 8N0B
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113. In microwave circuits, a waveguide is 116. In an FM system, a carrier of 100 MHz
is modulated by a sinusoidal signal
of 5 KHz. The bandwidth by Carson’s
approximation is 1 MHz. If, then by using
Carson’s approximation, the bandwidth of
y(t) around 300 MHz and the spacing of
spectral components are, respectively
(A) 1 MHz, 5 KHz
(B) 1 MHz, 15 KHz
114. In a microwave test bench, why is the (C) 3 MHz, 15 KHz
microwave signal amplitude modulated at
(D) 3 MHz, 5 KHz
1 KHz ?
(A) Because crystal detector fails at
117. A step-down chopper is operated in the
microwave frequencies
continuous conduction mode in steady
(B) To transmit the signal to a far-off state with a constant duty ratio D. If V 0 is
place the magnitude of the DC output voltage
and if Vs is the magnitude of the DC input
(C) To study amplitude modulation V
voltage, the ratio 0 is given by
Vs
(D) To increase the sensitivity of
D
measurement (A)
1 D
(B) 1 – D
1
115. A 1 mW video signal having a bandwidth (C)
1 D
of 100 MHz is transmitted to a receiver
(D) D
through a cable that has 40 dB loss. If the
effective one-sided noise spectral density
at the receiver is 10–20 Watt/Hz, then 118. What is the purpose of a slotted line in
signal to noise ratio of the receiver is microwave measurements ?
(A) Increase signal bandwidth
(A) 60 dB
(B) Measure frequency of the signal
(B) 30 dB
(C) Generate microwave signals
(C) 40 dB
(D) Measure voltage standing wave
(D) 50 dB patterns
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119. White Gaussian noise is passed through 123. Which of the following demodulator can
be used for demodulating the signal
density function of the envelope of the t)cos 20000 t ?
(A) Envelope demodulator
(A) Rayleigh
(B) Poisson (B) Synchronous demodulator
(C) Gaussian (C) Square law demodulator
(D) Uniform (D) None of the above
120. 124.
a very poor open loop voltage gain of 45
of power supply noise ? but is otherwise ideal. The gain of the
121. The cutoff frequency of a waveguide
depends upon
(A) 4.5
(A) The transverse and axial components
(B) 20
(B) The dielectric property of the medium (C) 4
in the waveguide (D) 5
(C) The characteristic impedance of the
waveguide
125.
(D) The cross-section of waveguide a dielectric material of relative permittivity
r
3 cm × 1.2 cm. The cut-off frequency for
122. What is the purpose of reducing the the dominant mode is
side lobe level in an antenna’s radiation
pattern ? (A) 12.5 GHz
(B) 5 GHz
(B) Enhance directivity
(C) 10 GHz
(C) Minimize interference and noise
(D) All of the above (D) 2.5 GHz
02/GO/CC/M-2025 – 12/I -44-
Official key not published for this paper.
Page 1 of 48
Source: Bihar Public Service Commission. Question paper published by Bihar Public Service Commission.