ELECTRONIC SCIENCE
Paper – III
Note : This paper contains seventy five (75) objective type questions of two (2) marks each. All questions are compulsory.
1. A triangular pulse is given at the input of an integrator circuit, the output will be of the form
(A) Square wave
(B) Triangular wave
(C) Parabolic
(D) Impulse
2. In an RC phase shift oscillator the frequency of oscillation is given by
3. IC LM 380 is a
(A) Voltage regulator
(B) Rectifier
(C) Power audio amplifier
(D) Schmitt trigger
4. The directivity of an antenna is 30 and it operates at a frequency of 100 MHz. The value of maximum effective aperture is given by
(A) 2.148 m2
(B) 21.48 m2
(C) 214.8 m2
(D) 0.2148 m2
5. A coaxial cable has characteristic impedance of Z0 = 75 Ω and a capacitance of 70 PF/m. The inductance of the coaxial per metre length is given by
(A) 3.937 μH/m
(B) 39.37 μH/m
(C) 0.3937 μH/m
(D) 393.7 μH/m
6. The value of radiation resistance of a Hertizian dipole of length 
is given by
(A) 0.493 Ω
(B) 0.219 Ω
(C) 12.3 Ω
(D) 0.123 Ω
7. An LVDT has the following data :
input = 6.3 V, Output = 5.2 V, range = ± 0.5 cm. The value of output voltage, when it is at 0.45 cm from the centre is given by
(A) 4.68 V
(B) 0.468 V
(C) 4.68 mV
(D) 46.8 mV
8. The Boolean expression 
simplifies to
9. In the circuit shown below, the output Y1 and Y2 for the given initial condition Y1 = Y2 = 1 and after four input pulses will be
(A) Y1 = 1, Y2 = 1
(B) Y1 = 1, Y2 = 0
(C) Y1 = 0, Y2 = 1
(D) Y1 = 0, Y2 = 0
10. Number of flip-flops needed to construct a shift register capable of storing decimal numbers upto 32 are
(A) 6
(B) 5
(C) 4
(D) 3
11. A carrier is frequency modulated with a sinusoidal signal of KHz resulting in a maximum frequency deviation of
5 KHz. Modulation index and bandwidth of the modulating signal is respectively is given as
(A) mf = 1, BW = 10 KHz
(B) mf = 2, BW = 12 KHz
(C) mf = 2.5, BW = 14 KHz
(D) mf = 1.7, BW = 14 KHz
12. Frequency in UHF range propagated by means of
(A) Ground wave
(B) Space wave
(C) Sky wave
(D) Surface wave
13. According to Hartley’s law
(A) The maximum rate of information depends on the channel bandwidth
(B) The maximum rate of information depends on the depth of modulation
(C) Redundancy is essential
(D) Only binary codes can be used
14. The error detector element in a control system gives
(A) The sum of the reference signal and the feedback signal
(B) The sum of the reference signal and the error signal
(C) The difference of the reference signal and the feedback signal
(D) The difference of the reference signal and the output signal
15. From the location of the roots of S-plane, determine the stability of the system :
(A) (i) stable, (ii) unstable, (iii) sustained oscillation
(B) (i) stable, (ii) sustained oscillation (iii) unstable
(C) (i) unstable, (ii) stable (iii) sustained oscillation
(D) (i) sustained oscillation, (ii) unstable (iii) stable
16. The most important application of tunnel diode is
(A) as rectifier
(B) as switching device in digital circuits
(C) as voltage controlled device
(D) as oscillator
17. The value of Numerical Aperture in case of optical fiber is
(A) > 1
(B) < 1
(C) = 1
(D) = 0
18. The threshold voltage of an n-channel MOSFET can be increased by
(A) increasing the channel doping concentration
(B) reducing the channel doping concentration
(C) reducing the gate oxide thickness
(D) reducing the channel length
19. Which semi conductor device acts like a diode and two resistors ?
(A) Triac
(B) SCR
(C) Diac
(D) UJT
20. After firing an SCR, if the gate pulse is removed, the SCR current
(A) remains the same
(B) reduces to zero
(C) enter into conduction mode
(D) rises a little and then falls to zero
21. The core of an optical fiber has
(A) a lower index of refraction than the cladding
(B) a lower index of refraction than air
(C) a higher index of refraction than the cladding
(D) refractive index equal to air
22. The core diameter of single mode fiber is in the order of
(A) 100 μm
(B) 10 μm
(C) 1 Å
(D) 1 nm
23. Laplace transform of e–at sin wt is
24. Fourier transform or Fourier integral of a function f(t) is given by
25. Find the output of the program
(A) 10 and 20
(B) 11 and 21
(C) 20 and 40
(D) 21 and 41
26. The function “isalnum( )” returns a non-zero value if the character is alphanumeric and zero otherwise.
What is header file to be used in the main program ?
(A) stdio.h
(B) io.h
(C) ctype.h
(D) string.h
27. To read a integer variable, find the correct format given below :
Int m;
(A) scanf (“\n %d”, m);
(B) scanf (“\n %s, m);
(C) scanf (“\n %c”, m);
(D) scanf (“\n %d”, & m);
28. 
In 8255 programmable peripheral interface device, if the port A and port B are to be set in a hand shake mode along with port C, what are the bits in the 8 bit control word to be set as 0 1 0.
(A) D6, D5 and D2
(B) D5, D4 and D1
(C) D6, D3 and D2
(D) D5, D2 and D1
29. The number system for the machine code of the microprocessor 8085 is
(A) BCD
(B) Octal
(C) Binary
(D) Hexadecimal
30. Which of the options in a multipurpose instruction used to implement the interrupt of 8085 and serial data input ?
(A) SOD
(B) SIM
(C) EJ
(D) RST 7.5
31. A thermistor is used to measure the temperature. Following characteristics are given
1. They exhibit positive temperature coefficient and poor sensitivity.
2. They exhibit negative temperature coefficient for resistance.
3. Their resistance decreases with the increase in temperature.
4. They are made of oxides of semi conductors.
Which one of the following is correct ?
(A) 1 & 4 only
(B) 1 & 3 only
(C) 2, 3 & 4
(D) 1, 3 and 4
32. In an FET, following characteristics are given :
Which one of the following is true ?
(A) 1 and 4
(B) 3 and 4
(C) 1 and 3
(D) 2 and 3
33. For a steady magnetic fields, which of the following is true :
1. The tangential component of magnetic field is continuous across any boundary except the surface of perfect conductor.
2. The tangential component of magnetic flux density is continuous across any boundary.
3. The normal component of magnetic flux density is continuous across any boundary.
4. The normal component of electric field is continuous across the boundary.
Which one of the following is correct ?
(A) 1 and 2
(B) 1 and 3
(C) 1 and 4
(D) 3 and 4
34. Given below are three types of converters :
(i) Successive approximation type
(ii) Weighted-resistor type
(iii) R-2R converters
(iv) Multiplexer
Which of these types are D to A converters ?
(A) Only (i) and (ii)
(B) Only (ii) and (iii)
(C) Only (ii) and (iv)
(D) Only (iii) and (iv)
35. Consider the following :
(i) Pulse – position – modulation
(ii) Pulse – Code – modulation
(iii) Pulse – Width modulation
(iv) Delta Modulation
The output of which of these in not digital ?
(A) (i) and (ii)
(B) (ii) and (iii)
(C) (i) and (iii)
(D) (i), (ii) and (iii)
36. Consider the following statements : A multiplexer :
1. selects one of the several inputs and transmits it to a single output.
2. routes the data from a single input to one of many outputs.
3. converts parallel data into serial data.
4. is a combinational circuit.
Which of these statements are correct ?
(A) 1, 2 and 4
(B) 2, 3 and 4
(C) 1, 3 and 4
(D) 1, 2 and 3
37. Consider the following statements : Losses in optical fibers are caused by
1. Impurities in the fibre material
2. Microbending
3. Splicing
4. Step index profile
Of these statements :
(A) 1, 3 & 4 are correct.
(B) 2, 3 & 4 are correct.
(C) 1, 2 & 3 are correct.
(D) 1, 2 & 4 are correct.
38. Consider the following statements : If an electric field is applied to an ntype semiconductor bar, the electrons
and holes more in opposite directions due to their opposite charges. The net current is
1. due to both electrons and holes with electrons as majority carriers.
2. the sum of electron and hole currents.
3. the difference between electron and hole current.
Which of these statements is/are correct ?
(A) 1 alone
(B) 1 and 2
(C) 2 and 3
(D) 3 alone
39. The state space approach is best suited technique for a complex system. It comprises of
(i) Many inputs
(ii) Many outputs
(iii) With no initial conditions
(iv) Reduces the complexity of mathematical expressions
(A) (i), (ii) and (iii)
(B) (i), (ii) and (iv)
(C) (ii), (iii) and (iv)
(D) (i), (iii) and (iv)
40. Both 8155 and 8255 programmable peripheral interface ICS have the following common features :
(i) Programmable I/Os
(ii) Either port A or Port B can be set as either input or output ports.
(iii) One 14-bit down counter
(iv) AD0 – AD7 are multiplexed address/datalines.
(A) (i), (ii) and (iii)
(B) (i), (ii) and (iv)
(C) (i), (iii) and (iv)
(D) (ii), (iii) and (iv)
41. Consider the following ICs :
1. LM 78 05
2. LM 78 15
3. LM 78 12
The correct sequence of the output noise voltage (at 25 °C and for an operating frequency range of 10 Hz ≤ f ≤ 100 KHz) in decreasing order is given by
(A) 2, 1, 3
(B) 2, 3, 1
(C) 1, 2, 3
(D) 3, 1, 2
42. Consider the following bands/waves :
1. L band
2. C band
3. Ku band
4. Ka band
Arrange them in increasing frequency order, the correct sequence of the ascending order in terms of frequency is
(A) 1, 2, 3, 4
(B) 4, 3, 2, 1
(C) 1, 3, 2, 4
(D) 4, 2, 3, 1
43. The correct sequence of components in any transmission system is
(i) Modulation
(ii) Base band Multiplexing
(iii) Up converter
(iv) IF amplifier
Codes :
(A) (iv), (iii), (ii), (i)
(B) (iii), (i), (ii), (iv)
(C) (ii), (i), (iv), (iii)
(D) (i), (ii), (iii), (iv)
44. The step, ramp and parabolic test input signals can respectively be expressed as
45. Arrange in ascending order based on power dissipation the following logic families :
(i) ECL
(ii) TTL
(iii) CMOS
Codes :
(A) (i), (ii), (iii)
(B) (iii), (ii), (i)
(C) (i), (iii), (ii)
(D) (iii), (i), (ii)
46. Consider the following rectifier circuits :
1. Half-wave rectifier without filter
2. Full-wave rectifier without filter
3. Full-wave rectifier with series inductance filter
4. Full-wave rectifier with capacitance filter
The sequence of these rectifier circuits in decreasing order of the ripple factor is
(A) 1, 2, 3, 4
(B) 3, 4, 1, 2
(C) 1, 4, 3, 2
(D) 3, 2, 1, 4
47. The correct sequence of sub-systems of Klystron amplifiers as they appear in the direction of flow of electron beam is
(A) Buncher cavity, Cathode, Collector, Catcher cavity
(B) Buncher cavity, Cathode, Catcher cavity, Collector
(C) Cathode, Buncher cavity, Catcher cavity, collector
(D) Cathode, Buncher cavity, collector, Catcher cavity
48. In a closed loop automatic control system, the sequence of operations is as follows :
(i) Controlling unit
(ii) Correcting unit
(iii) Impact on the process
(iv) Measurement of process parameters
(A) (iii), (ii), (i) and (iv)
(B) (iv), (i), (ii) and (iii)
(C) (ii), (i), (iii) and (iv)
(D) (iv), (ii), (i) and (iii)
49. Find the correct list, which is the reverse (at all levels) of the given list : [[4, 7, 8], 2, 9, [19, 6], 20, 3]
(i) 3, 20
(ii) 9, 2
(iii) [6, 19]
(iv) [8, 7, 4]
(A) (ii), (iii), (iv) & (i)
(B) (i), (iv), (iii) & (ii)
(C) (i), (iii), (ii) & (iv)
(D) (i), (ii), (iii) & (iv)
50. Each instruction in an assembly program has the following fields :
(i) Lable field
(ii) Operand field
(iii) Comment field
(iv) Mnemonic field
Please write the proper sequence of fields :
(A) (i), (ii), (iii) & (iv)
(B) (i), (iv), (ii) & (iii)
(C) (iii), (i), (iv) & (ii)
(D) (iii), (iv), (ii) & (i)
51. Match the following lists :
52. Match the following lists :
53. Match the following lists of various thermocouples & sensitivity:
54. Match the following lists :
55. Match the following :
56. Match the following :
57. Match the following :
58. The mnemonic of 8085 processor indicate :
59. The stability of the system for different locations of poles and zeroes :
60. Match the following :
Directions : Q. Nos 61 to 70 : The following items consist of two statements, one labelled the “Assertion (A)” and the
other labelled the “Reason (R)”. You are to examine these two statements carefully and decide if the Assertion (A) and the Reason (R) are individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answers to these items using the codes given below and mark your answer accordingly.
Assertion (A) :
Reason (R) :
Codes :
(A) Both (A) and (R) are correct and (R) is correct explanation of (A).
(B) Both (A) and (R) are correct, but (R) is not correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.
61. Assertion (A) : TWTA is a narrow band device and has a helical structure and it is used as amplifier and oscillator.
Reason (R) : In TWT, the electron beam travels through a slow-wave structure and speed of electron beam is 1/10 of the velocity of light.
62. Assertion (A) : An Op-Amp is a direct coupled high gain amplifier.
Reason (R) : It consists of one or more differential amplifiers and usually followed by a level translator and push pull stage.
63. Assertion (A) : To have a high sensitivity, a low value of gauge factor is desirable.
Reason (R) : Semi-conductor strain gauges are made up of Si and Ge and show piezoresistive effect.
64. Assertion (A) : In amplitude modulation technique the modulation index should be close to 1.
Reason (R) : The power carried by message signal in the side bands increases with increase in modulation index.
65. Assertion (A) : In logic circuit, positive logic is represented by logic “0” voltage level is lower than logic “1” voltage level.
Reason (R) : Excess 3 code is known as self complementary code.
66. Assertion (A) : A self-biased circuit has a better stability than a fixed bias circuit.
Reason (R) : It provides negative feed back by the use of an additional resistor between the base and ground.
67. Assertion (A) : Optical fibers have broader bandwidth compared to conventional copper cables.
Reason (R) : Low power LASER beams are considered to be very powerful as compared to high power ordinary light beams.
68. Assertion (A) : A demultiplexer can be used as a decoder.
Reason (R) : A demultiplexer is built by using AND gates only.
69. Assertion (A) : In serial communication system, when the transmission of data goes in both ways, it is called
full-duplex system. Now if two micro processors are connected in full duplex mode, the amount of data transmitted will be double to the amount of data in half-duplex mode connection.
Reason (R) : When the transmission of data goes in one way, it is called halfduplex system and when the data moves in both ways, it is called full duplex system.
70. Assertion (A) : In control systems, steady state response in the final requirement for calculating the efficiency of the system.
Reason (R) : The transient response is also critical for the determination of the steady state response.
Read the paragraph and answer the question 71 to 75 :
Microwave tubes are used as microwave amplifiers and oscillators. Three general type of microwave tubes in which third type tubes are important because in these tubes there is an interaction between an electron and an RF field is continuous. The Travelling Wave Tube (TWT) is the prime example of this interaction. It is an amplifier, whose oscillator counter part is called Backward Wave Oscillator (BWO). The second sub-group consists of tubes in which a magnetic field ensures a constant electron beam – RF field interaction, and this is complemented by the Cross-Field Amplifier (CFA). Multicavity Klystron is used as high and very high power amplifiers in the UHF and microwave ranges. The frequency range covered is from about 250 MHz to over 95 GHz. The reflex-Klystron is a low power microwave oscillator. It is assumed that oscillations are started by switching transients. For oscillations to be maintained the transient time in the repeller space cycle is given as 
where n is an integer, each value of n is said to correspond to different reflex klystron mode. Reflex Klystrons with integral cavities are available in the frequency range 4 to 200 GHz.
71. One of the reasons why vacuum tubes eventually fail at microwave frequencies in that their
(A) transit time becomes too short
(B) shunt capacitive reactance becomes too large
(C) series inductive reactance becomes too small
(D) noise figure increases
72. The Multicavity Klystron
(A) is not low-level amplifier because of noise
(B) has a high repeller voltage to ensure a rapid transit time.
(C) is not suitable for pulsed operation
(D) needs a long transit time through the buncher cavity to ensure current modulation
73. The primary of the helix in a travelling wave tube is to
(A) prevent the electron beam from spreading in the long tube
(B) reduce the axial velocity of the RF field
(C) ensure broadband operation
(D) reduce the noise figure
74. One of the following is unlikely to be used as a pulsed device. It is the
(A) TWT
(B) CFA
(C) BWO
(D) Multicavity Klystron
75. Indicate the false statement. Klystron amplifiers may use intermediate cavities to
(A) prevent the oscillations that occur in two cavity Klystrons
(B) increase the bandwidth of the device
(C) improve the power gain
(D) increase the efficiency of the Klystron
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