ELECTRONIC SCIENCE
PAPER – III
Note : This paper contains seventy five (75) objective type questions of two (2) marks each. All questions are compulsory.
1. In zone refining process if K is the distribution coefficient, CS represents the concentration of dopant in solid phase and CL represents the concentration of dopant in the liquid phase then K is defined as :
(1) K=CS/CL
(2) K=CL/CS
(3) 
(4) 
2. Barrier height in a metal-semiconductor contact can easily be estimated from :
(1) (1/C) versus V curve
(2) (1/C2) versus V curve
(3) (1/C) versus I curve
(4) (1/C2) versus I curve
3. Two coils having equal resistances but different inductances (Say L1 and L2) having time constants τ1 and τ2 respectively, are connected in series. The time constant, ‘τ’ of the series combination is :
(1) 
(2) 
(3) 
(4) 
4. The rms voltage measured across each of the circuit elements in the figure given below is shown. When the circuit is excited using a sinusoidal source ‘es’, the rms value of the source voltage ‘es’ is :
(1) 1 V
(2) 4 V
(3) 5 V
(4) 10 V
5. For a given JFET, the typical values of amplification factor and transconductance are given as 40 and 100 μs respectively. The dynamic drain resistance of JFET will be :
(1) 200 Ω
(2) 400 Ω
(3) 200 kΩ
(4) 400 kΩ
6. For a given n-MOS capacitor with substrate doping of NA=1017 cm−3, oxide thickness 20 nm, εox=3.9 εo the values of oxide capacitance and flat band capacitance are respectively given as (use εo=8.85×10−14 F cm−1) :
(1) 142 nF/cm2 and 172 nF/cm2
(2) 172 nF/cm2 and 142 nF/cm2
(3) 71 nF/cm2 and 86 nF/cm2
(4) 86 nF/cm2 and 71 nF/cm2
7. A three bit shift register is shown below to have content 000 again, the number of clock pulses required would be :
(1) 2
(2) 3
(3) 6
(4) 7
8. If (11X1Y)8=(12C9)16, then the respective values of X and Y are :
(1) 1 and 5
(2) 3 and 1
(3) 5 and 7
(4) 7 and 5
9. The flag which indicates whether the interrupt that may occur at the interrupt pins of 8086 will actually be served or not is :
(1) Direction flag
(2) Interrupt enable flag
(3) Trap flag
(4) Overflow flag
10. The timer of 8155 consists of __________ counter and operates in __________.
(1) 14 bit, 4 modes
(2) 16 bit, 8 modes
(3) 14 bit, 8 modes
(4) 16 bit, 4 modes
11. Consider the following program of ‘C’
The output of the program is :
(1) 1 2 3 4 5 6 7 8
(2) 1 2 3 3 5 5 7 8
(3) 1 2 2 3 3 4 4 8
(4) None of the above
12. Assuming a 2-byte integer which of the following is the correct output for the program given below ?
(1) 0 0 0 0
(2) f f f f
(3) f f f 8
(4) 0 0 0 8
13. A transmitting antenna of 100 m height radiates 40 kW at a frequency of 100 MHz uniformly in Azimuth plane. If the height of receiver antenna is 16 m, the value of Line of sight distance is given by :
(1) 25 km
(2) 57.68 km
(3) 27.68 km
(4) 114 km
14. The intrinsic impedance of a Lossy dielectric medium is given by :
(1) 
(2) 
(3) 
(4) 
15. The highest modulating signal frequency that can be demodulated by a peak detector without attenuation is given by.
(1) 
(2) 
(3) 
(4) 
16. In digital companding, the analog signal is :
(1) First converted to a linear PCM Code and then sampled.
(2) First sampled and then converted to a linear PCM Code.
(3) First sampled and then converted to a non – linear PCM Code.
(4) Never sampled.
17. A Buck – converter is :
(1) AC to DC converter
(2) AC to AC converter
(3) DC to DC converter
(4) DC to AC converter
18. A certain Helium Neon Laser emitting at 633 nm has a line width of 0.002 nm. The coherence length of the laser is given by :
(1) 40 cm
(2) 5 cm
(3) 20 cm
(4) 10 cm
19. The root-locus of a typical transfer function is given as
The polar plot of the transfer function will be :
(1) 
(2) 
(3) 
(4) 
20. The characteristics polynomial of a control system is given as
q(s)=s4+s3+s2+s+k
The system is :
(1) Stable for all values of k
(2) Stable for positive values of k
(3) Unstable for all values of k
(4) Unstable for only positive values of k
21. Conductivity of a semiconductor depends upon :
(a) doping density
(b) mobility of charge carriers
(c) Length of semiconductor
(d) Shape of semiconductor
Code :
(1) (a), (b) and (c) are correct
(2) (b), (c) and (d) are correct
(3) (a) and (c) are correct
(4) (a) and (b) are correct
22. A zener diode :
(a) has sharp breakdown at low forward voltage
(b) has sharp breakdown at low reverse voltage
(c) can be used for voltage regulation
(d) has a negative resistance region
Code :
(1) (a), (c) and (d) are correct
(2) (b), (c) and (a) are correct
(3) (a) and (b) are correct
(4) (b) and (c) are correct
23. Consider the following statements associated with resonant frequency :
(a) For a series RLC circuit, current is maximum
(b) For a series RLC circuit, voltage across C is minimum
(c) For a series RLC circuit, current is minimum
(d) For a parallel RLC circuit, total impedance is maximum
Which one of the above statement are correct ?
(1) (a), (b) and (d) only
(2) (b) and (d) only
(3) (a) and (d) only
(4) (a) and (b) only
24. Consider the following statements for the hybrid parameters :
(a) h11 is called input impedance with output shorted
(b) h21 is current gain with output shorted
(c) h12 is voltage feedback ratio with input terminals shorted
(d) h22 is output admittance with input terminal open
Which of the statements given above are correct ?
(1) (a), (b) and (c) only
(2) (a), (c) and (d) only
(3) (a), (b) and (d) only
(4) (a), (b), (c) and (d)
25. The capacitance of a reverse biased PN junction :
(a) increases as reverse bias is increased
(b) increases as reverse bias is decreased
(c) does not change by increasing or decreasing the reverse bias
(d) can be used for varactor diode application
Code :
(1) (a), (c) and (d) are correct
(2) (b), (c) and (d) are correct
(3) (b) and (d) are correct
(4) (a) and (c) are correct
26. For making an Oscillator certain conditions are to be met in an amplifier :
(a) −ve feedback
(b) +ve feedback
(c) Barkhausen criteria
(d) Noise signal
Code :
(1) (b), (d), (c) is correct
(2) (a), (d), (c) is correct
(3) (a), (c) is correct
(4) (b), (a), (c) is correct
27. Which of the following statements regarding binary counters are correct ?
(a) Clock inputs of all the flip – flops of a synchronous counter are applied from the same source whereas those in an asynchronous counters are from different sources.
(b) Asynchronous counter has ripple effects whereas synchronous counter has not.
(c) Only J-K flip-flops can be used in synchronous counters whereas asynchronous counters can be designed with any kind of flip flops.
(d) Latches can be used for designing asynchronous counters.
Code :
(1) (a), (b) and (d) only
(2) (a), (b) and (c) only
(3) (b) and (d) only
(4) (a), (c) and (d) only
28. Consider the following statements :
A multiplexer
(a) Selects one of the several inputs and transmits it to a single output
(b) Routes the data from a single input to many outputs
(c) Converts parallel data into serial data
(d) Is a combinational circuit
Which of these statements are correct ?
(1) (a), (b) and (d) only
(2) (b), (c) and (d) only
(3) (a), (c) and (d) only
(4) (b) and (c) only
29. Which of the following statements on DRAM are correct ?
(a) Page mode read operation is faster than RAS read.
(b) RAS input remains active during column address strobe.
(c) DRAM cell occupies more space than SRAM cell.
(d) Static power is dissipated for storing charge in a capacitance.
The correct answer is :
(1) (a) and (b)
(2) (c) and (d)
(3) (a) and (d)
(4) (b) and (c)
30. Which of the following are control/handshake signal in mode 1 of 8255 ?
(a) OBF
(b) IBF
(c) STB
(d) BSR
Code :
(1) (a) and (d)
(2) (a), (b) and (c)
(3) (b), (c) and (d)
(4) (a), (b) and (d)
31. Which of the following statements are correct about the program given below ?
(a) K2 cannot be initialized as shown
(b) K1 can be initialized as shown
(c) to initialize char C[ ] of K2 ‘.’ operator should be used
(d) results in syntax error
The correct answer is :
(1) (a) and (b) only
(2) (b) and (c) only
(3) (a), (b) and (c)
(4) (a), (c) and (d)
32. Consider the following definition of array in C :
Which of the following expressions would give value 1 for the array defined above ?
(a) a[0] [0] [0]
(b) * * * a
(c) * * * a[0]
(d) * * a[0] [0]
The correct answer is :
(1) (a) and (c)
(2) (a) and (d)
(3) (a) and (b)
(4) (c) and (d)
33. A Series inverter with series Load deliver a load power of 1 kW at resonance. The value of Load resistance = 10 Ω and resonant frequency is 20 kHz, Q factor = 3.85.
For this, the value of Capacitor and inductor are estimated. Following are the values of L and C :
(a) L = 306.37 μH
(b) C = 0.2067 μF
(c) L = 3.06 μH
(d) C= 20.67 μF
Out of above, which are correct ?
(1) (a) and (b)
(2) (b) and (c)
(3) (c) and (d)
(4) (a) and (d)
34. In SONET standards, following are the data rates and payloads :
(a) SONET – OC – 1 data rate 51.84 Mbps
(b) OC – 1, payload 40.112 M bits/s
(c) OC – 1 data rate 50.112 Mbps
(d) OC – 1 payload 50.112 Mbps
Which of the above is correct for OC – 1 ?
(1) (a) and (b)
(2) (b) and (c)
(3) (c) and (d)
(4) (a) and (d)
35. Consider the following formulas with all the symbols having usual meanings :
Which of the above are incorrect ?
(1) (a) and (b)
(2) (b) and (c)
(3) (c) and (d)
(4) (a) and (d)
36. Read the following statements :
(a) A channel is said to be ideal, if, within the bandwidth occupied by the transmitted signal, the amplitude response is constant and phase response is a linear function of frequency.
(b) A channel is said to be ideal, if, within the bandwidth occupied by the transmitted signal, both amplitude and phase response are linear function of frequency.
(c) It is possible to compensate for the non-ideal frequency response characteristics of the channel by use of filter at the demodulator.
(d) A non-ideal channel does not exist.
Which of the above statements are correct ?
(1) (a) and (c) Only
(2) (a) and (d) Only
(3) (b) and (d) Only
(4) (b) and (c) Only
37. An X – band pulse cylindrical magnetron has following parameters :
Anode voltage = 26kV, Beam current = 27A, Magnetic flux density = 0.336 Wb/m2
Radius of Cathode Cylinder = 5 cm, Radius of Vane edge to center = 10 cm.
Following data regarding angular frequency and Cut off voltage is given.
(a) angular frequency = 5.91×1010 rad
(b) Cut off voltage = 139.50 kV
(c) angular frequency = 3.91×109 radian
(d) Cut off voltage = 239.39 kV
Which is a correct option ?
(1) (a) and (b)
(2) (b) and (c)
(3) (c) and (d)
(4) (d) and (a)
38. A TE11 mode is propagating through a circular waveguide of radius of 5 cm. The dielectric in the waveguide is air. For this following are the datas.
(a) Cut off wave number = 38.62
(b) Cut off frequency = 1.758 GHz
(c) Cut off wave number = 36.82
(d) Cut off frequency = 2.758 GHz
Out of these following are correct :
(1) (a) and (b)
(2) (b) and (c)
(3) (c) and (d)
(4) (a) and (d)
39. Read the following statements :
(a) A function G(s) of the complex variables ‘S’ is called an analytic function in a region of the S-plane if the function and all its derivatives exist in the region.
(b) A function G(s) of the complex variable ‘S’ is called an analytic function in a region of the S-plane if function and all its derivatives do not exist in the region.
(c) The singularities of a function are the points in the S-plane at which the function and its derivatives do not exist.
(d) The singularities of a function are the points in the S-plane at which the function and its derivatives exist.
Which of the above statements are not correct ?
(1) (a) and (b)
(2) (b) and (c)
(3) (b) and (d)
(4) (a) and (d)
40. A force with which the plates of a parallel plate capacitor having charge Q and area of each plate A, attract each other is :
(a) Directly proportional to Q
(b) Inversely proportional to Q
(c) Directly proportional to Q2
(d) Inversely proportional to A
Which of the above are correct ?
(1) (a) and (d) Only
(2) (b) and (d) Only
(3) (c) and (d) Only
(4) (a), (c) and (d) Only
41. Match the following list :
42. Match the following list :
43. Match the following list :
44. Match the following list :
45. Match the following list :
46. Match the following list :
47. Match the following lists in terms of Microwave bands :
48. Match the following list :
49. Match the following list :
50. Match the following list :
51. A given semiconductor is doped by phosphorous at different doping concentrations (given below).
(a) 2×1012 cm−3
(b) 4×1014 cm−3
(c) 3×1013 cm−3
(d) 2×1015 cm−3
Sequence them in terms of decreasing conductivity :
(1) (a), (b), (c), (d)
(2) (d), (b), (c), (a)
(3) (b), (a), (d), (c)
(4) (d), (c), (a), (b)
52. What are the steps required in sequence to solve a circuit using super position theorem ?
(a) Select any one source and short circuit all other voltage sources.
(b) Find out the current or voltage across the required element, due to the source under consideration.
(c) Open all current sources, if internal impedance is not known. If known replace them by their impedances.
(d) Add all the individual effects produced by individual sources to obtain the total current in or across the voltage element.
Code :
(1) (a), (c), (b), (d)
(2) (a), (b), (c), (d)
(3) (c), (a), (b), (d)
(4) (a), (d), (c), (b)
53. Following are the amplifying systems available.
(a) CB transistor amplifier
(b) CC transistor amplifier
(c) CE transistor amplifier
(d) OP Amp
Sequence in terms of increasing order of voltage gain.
(1) (b), (a), (c), (d)
(2) (d), (c), (a), (b)
(3) (a), (b), (c), (d)
(4) (c), (d), (b), (a)
54. The correct sequence of shifting binary number through bidirectional shift register is :
(a) All the lower registers are reset i.e. set=0 by giving a pulse at the reset terminals.
(b) The contents of the lower register are gated up directly to the upper register.
(c) The upper register is reset for the next shift operation.
(d) The contents of the upper register are gate down to the lower register either one position to the right or to the left as desired.
Code :
(1) (a), (c), (b), (d)
(2) (b), (a), (c), (d)
(3) (b), (a), (d), (c)
(4) (a), (c), (d), (b)
55. Arrange the following operations of DMA to transfer a block of data.
(a) Terminal count register is decremented by one with each byte of data transfer till it reaches to zero.
(b) DMA controller acquires bus system and starts transferring the data.
(c) Microprocessor suspends its operations, release the buses and generates HLDA.
(d) DMA controller sends HOLD
The correct sequence is :
(1) (d), (b), (c), (a)
(2) (d), (c), (b), (a)
(3) (d), (c), (a), (b)
(4) (c), (d), (b), (a)
56. Arrange the following operators in the precedence order of highest to lowest :
(a) ==
(b) ++
(c) %
(d) &
The correct order of precedence is :
(1) (d), (b), (c), (a)
(2) (b), (c), (a), (d)
(3) (a), (d), (b), (c)
(4) (c), (a), (d), (b)
57. Following are various layers in atmosphere used for communications :
(a) F2 Layer
(b) D layer
(c) F1 Layer
(d) E Layer
Arrange these in terms of descending order of their height from earth.
The correct sequence is :
(1) (a), (c), (d), (b)
(2) (b), (c), (d), (a)
(3) (a), (b), (d), (c)
(4) (c), (b), (a), (d)
58. Consider the following detector circuits.
(a) Diode detector
(b) Slope detector
(c) Balanced slope detector
(d) Ratio detector
Arrange the above detectors in decreasing order of their circuit complexity :
(1) (d), (b), (c), (a)
(2) (a), (b), (c), (d)
(3) (c), (d), (b), (a)
(4) (d), (c), (b), (a)
59. Following are the wavelength bands used in optical communication systems.
(a) Long (L) Band
(b) Conventional band (C band)
(c) Extended band (E band)
(d) Original band (O-band)
Arrange them in increasing order of wavelengths. The correct sequence is :
(1) (d), (c), (b), (a)
(2) (c), (b), (a), (d)
(3) (b), (c), (a), (d)
(4) (a), (b), (c), (d)
60. Consider the following piezoelectric materials.
(a) Quartz
(b) Tourmaline
(c) Lithium sulphate
Arrange the above piezoelectric materials in decreasing order of their useful temperature ranges :
(1) (a), (b), (c)
(2) (a), (c), (b)
(3) (b), (a), (c)
(4) (b), (c), (a)
Directions : Question No. 61 to 70 :
The following items consist of two statements, one labelled as “Assertion (A)” and the other labelled as the “Reason (R)”. You are to examine the 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 answer to these items using the codes given
below and mark your answer accordingly.
Code :
(1) Both (A) and (R) are true and (R) is the correct explanation of (A).
(2) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(3) (A) is true, but (R) is false.
(4) (A) is false, but (R) is true.
61. Assertion (A) :
A p-n junction diode with low junction depth can be used as solar cell when illuminated by suitable light (wavelength) at top thin layer above the junction.
Reason (R) :
A p-n junction diode under no condition can be used as solar cell. It can be used only as light emitting diode for optoelectronic applications.
62. Assertion (A) :
Superposition theorem can be used to find the output of a full wave rectifier excited by sinusoidal signal sources of different frequencies connected in series.
Reason (R) :
Superposition theorem is valid for all linear systems.
63. Assertion (A) :
A UJT (Unijunction Transistor) finds application in making relaxation oscillator of certain given frequency.
Reason (R) :
It has three terminals like that of a transistor – corresponding to emitter base and collector. Therefore it can be used to make oscillator as well as amplifier.
64. Assertion (A) :
It is possible that a digital circuit gives the same output for different input voltages.
Reason (R) :
A digital circuit is also called logic circuit.
65. Assertion (A) :
The address bus size in 8086 is 20 bit.
Reason (R) :
Registers size of 8086 microprocessor is 16 bit.
66. Assertion (A) :
C++ is object – oriented programming language.
Reason (R) :
C++ supports class, inheritance, templates and exception handling.
67. Assertion (A) :
In power electronics, converters feel stress during the operation beyond their ratings.
Reason (R) :
The snubber circuits are used to increase the applied voltage across the devices during turn off transients.
68. Assertion (A) :
Sampling theorem forms the basis for the relation between continuous time signals and discrete time signals.
Reason (R) :
If the sampling is done at Nyquist rate, the signal x(t) can be reconstructed from the sample values x[n] = x[nTs]; −∞≤ n ≤∞.
69. Assertion (A) :
A reflex Klystron is a single cavity Klystron that overcomes the disadvantages of two cavity Klystron oscillator.
Reason (R) :
It is high power microwave generator operating beyond 60 GHz and generating powers in kWs. Its efficiency is very high of the order of 70%.
70. Assertion (A) :
Capacitive transducers are, infact, primary transducers for measurement of displacements.
Reason (R) :
A Capacitive transducer is a non loading, non contact and non-invasive type transducer for displacement measurements.
Based on the paragraph given below answer Q. 71 to 75 :
The traditional methods of combinational circuits involve simplification and realization using gates. Using these methods, complex functions have been integrated and are easily available in IC form. There is an attractive array of devices like multiplexer, demultiplexer, decoders, comparators, parity generators/checkers, which significantly reduce IC package count there by reducing the system cost. The system design is greatly simplified because the laborious and time consuming simplification methods are generally not required with these devices. This also improves the reliability of the system by reducing the number of external wired connection. But they have some limitations as well. Different memories like ROM, PROM can also be used to implement combinational circuits without much simplification.
71. The minimum number of selection lines required for selecting one of the 16 inputs are :
(1) 4
(2) 2
(3) 8
(4) 16
72. A logic circuit required for converting BCD Code to 7 segment Code is known as :
(1) Multiplexer
(2) Demultiplexer
(3) Decoder
(4) Encoder
73. In a BCD Subtractor if the sum of minuend and the nine’s complement of subtrahend is not a valid BCD Code, then which binary number is added to the sum to get the correct answer ?
(1) 1000
(2) 0001
(3) 0110
(4) 0111
74. Consider the following digital circuits :
(a) Multiplexers
(b) Read only memories
(c) D – Latch
(d) Circuit as shown.
Which of these come under the class of combinational circuits only ?
(1) (a) and (b)
(2) (c) and (d)
(3) (b) and (c)
(4) (b), (c) and (d)
75. A ROM is to be used to implement a “Squarer”, which outputs the square of a 3-bit number.
What must be the size of the ROM ?
(1) 8 – address lines and 9 data lines
(2) 3 – address lines and 6 data lines
(3) 3 – address lines and 9 data lines
(4) 8 – address lines and 6 data lines
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