### 2012 June UGC NET Examination in Electronic Science, Paper III: Previous Years Solved Question Paper Along With Answer Keys

3. Consider an n-channel depletion mode MOSFET having following parameters:
VTN = –2.5 V and Kn = 1.1 mA/V2
If VGS = 0V and VDS = 0.5 V, then current ID, is
(A) 9.96 mA
(B) 6.43 mA
(C) 2.48 mA
(D) 5.56 mA

4. The tie-set schedule gives relation between
(A) branch currents and link currents
(B) branch voltages and link currents
(C) branch currents and link voltages
(D) branch voltages and link voltages

6. The final value of 2S + 1 / S4 + 8S3 + 16S2 + S is
(A) 0
(B) ¥
(C) 1
(D) 2

7. If differential amplifier has a differential gain of 20,000. CMRR = 80 dB, then common mode gain is
(A) 2
(B) 1
(C) 1/2
(D) 0

8. For proper operation of integrators, its RC time constant and period T of the wave should be such that
(A) T >> RC
(B) T << RC
(C) T = RC
(D) T = 2 ln RC

9. The phase shift introduced by feed network or amplifier in Wein bridge oscillator is
(A) 0°
(B) 90°
(C) 180°
(D) 270°

10. For a certain logic family if VOL = 0.5 V, VIL = 1.2 V and VOH = 3.5 V, VIH = 2.8 V, then the noise margin is
(A) 3 V
(B) 1.7 V
(C) 1.3 V
(D) 0.7 V

12. Number of flip-flops needed to construct a shift register capable of storing decimal numbers upto 32 are
(A) 6
(B) 4
(C) 5
(D) 2

13. In the mode word format of 8251 during initialization, D6 and D7 bits as 0 and 1 signify
(A) 16 X Baud Rate
(B) Character length as 7 bits
(C) Parity enable and even parity
(D) No. of stop bits as 1(1/2)

14. The control word of ‘0B5H’ of 8253 indicates that the following counter is selected
(A) Counter 0
(B) Counter 1
(C) Counter 2
(D) Counter 3www.netugc.in

15. In 8051, Pin 30 (ALE / PROG), if this bit is set as logic zero (‘0’), it signifies
(B) For enabling internal ROM of programming
(C) For disabling internal ROM programming
(D) Both (A) and (C)

16. The expression a = 7/22 * (3.14 + 2) * 3/5 evaluates to
(A) 8.28
(B) 6.28
(C) 3.14
(D) 0

17. Which escape sequence takes the cursor to the beginning of the current line?
(A) \n
(B) \r
(C) \a
(D) \t

20. The depth of penetration of a wave in a lossy dielectric increases with increasing
(A) Conductivity
(B) Permeability
(C) Wavelength
(D) Permittivity

21. A very lossy, l/4 long, 50 ohm transmission line is open circuited at the load end. The input impedance measured at the other end of the line is approximately
(A) 0
(B) 50 ohm
(C) ¥
(D) 200 ohm

22. In the spectrum of frequency modulated wave
(A) The carrier frequency disappears when the modulation index is large.
(B) The amplitude of any side band depends on the modulation index.
(C) The total number of side bands depends on the modulation index.
(D) The carrier frequency cannot disappear.

23. Indicate which one of the following is not an advantage of FM over AM:
(A) Better noise immunity is provided
(B) Lower bandwidth is required
(C) The transmitted power is more useful
(D) Less modulating power is required

24. Indicate the noise source which belongs to category a different from that of the other three.
(A) Solar noise
(B) Cosmic noise
(C) Atmospheric noise
(D) Galactic noise

27. Dispersion shifted wavelength in optical fiber is
(A) 800 nm
(B) 1300 nm
(C) 1550 nm
(D) 400 nm

28. The problem, with PI controller is its response to transients, is
(A) very fast
(C) non-linear
(D) sluggish

29. Which is the most linear temperature transducer?
(A) Thermocouple
(B) RTD
(C) IC-sensor
(D) Thermistor

30. The variations in the ambient temperature effect the following parameters:
(A) Sensitivity
(B) Accuracy
(C) Stability
(D) Above all

31. Consider the following statements regarding a semiconductor:www.netugc.in
I. Acceptor level lies close to valence band.
II. Donor level lies close to valence band.
III. n-type semiconductor behaves as a conductor at 0 °K.
IV. p-type semiconductor behaves as an insulator at 0 °K.
(A) I and II are correct.
(B) I and III are correct.
(C) II and III are correct.
(D) I and IV are correct.

32. A network is said to be linear if and only if
I. Response is proportional to excitation function
II. Principle of superposition applies
III. Principle of homogeneity applies
IV. It is reciprocal
(A) Options I and II are correct.
(B) Options II and III are correct.
(C) Options III and IV are correct.
(D) Options I and IV are correct.

34. Which of the following statements are correct?
I. A flip – flop is used to store 1-bit =of information
II. Race-around condition occurs in a J-K flip – flop when both inputs are I.
III. A transparent latch consists of a D-type flip – flop
(A) I and II are correct.
(B) I and III are correct.
(C) I, II and III are correct.
(D) I, II and III are not correct.

36. Which of the following statements will store value 3 in the variable a?
I. a = 15% 4;
II. int a = (3 * 4) / (1 + 3) ;
III. int a = 3 ;
IV. int a = 6.0/2 ;
(A) Options I, II and III are correct.
(B) Options II, III and IV are correct.
(C) Options I and III are correct.
(D) Options II and IV are correct.

37. In a rectangular metallic waveguide
I. Guided wavelength is never less than the free space wavelength
II. TEM mode is possible if the dimensions are properly chosen
III. vp × vg = C2
IV. waves travel along all the four walls of the waveguide
(A) Options I and III are correct.
(B) Options III and IV are correct.
(C) Options II and III are correct.
(D) Options I and IV are correct.

38. Indicate the false statement in the case of Armstrong modulation system.
I. The system is basically phase and frequency modulation.
II. The system is also amplitude modulation.
III. Frequency multiplication must be used.
IV. Equalization is unnecessary.
(A) I and II are correct.
(B) I, II and III are correct.
(C) I and III are correct.
(D) III and IV are correct.

39. DIAC is a
I. 2 terminal unidirectional switch
II. 2 terminal bi-directional switch
III. 3 layers and no gate device
IV. 4 layers and no gate device
(A) Options II and III are correct.
(B) Options II and IV are correct.
(C) Options I and III are correct.
(D) Options I and IV are correct.

40. In a DVM, the accuracy of the measurement depends on I. No. of A/D conversions in a second.
II. The resolution of A/D converter.
III. A statistical processing of samples and a huge memory.
IV. Speed of the processor should be high.
(A) I, II and III are to be fulfilled
(B) II, III and IV are to be fulfilled
(C) I, III and IV are to be fulfilled
(D) I, II and IV are to be fulfilled

Assertion-Reason type questions:

Q. 41 to 50: 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 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 sheet accordingly.
Codes:
(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 and (R) is false.
(D) (A) is false and (R) is true.

41. Assertion (A): A BJT is said to be operating in a saturation region if both the junctions are forward biased.
Reason (R): In saturation region collector doping concentration is reduced.

43. Assertion (A): Schmit trigger employs positive feedback and has hysteresis property that helps to compare two voltage levels.
Reason (R): In some logic circuits rise and fall time play important role in switching. Schmit trigger improves the rise and fall time.

44. Assertion (A): The fan out of a CMOS gate is poor.
Reason (R): The current driving capability of CMOS is poor.

45. Assertion (A): In 8085 processor, lower byte of address bus and data bus are multiplexed. A latch is required to separate address lines and data lines.
Reason (R): Multiplexing makes processor slow speed and compact.

46. Assertion (A): Relational operators cannot be used to evaluate whether a condition evaluates to true (T) or false (F).
Reason (R): Use of ‘=’ as relational operator will form a syntax error.

48. Assertion (A): Radio and Television receivers are generally of superheterodyne type.
Reason (R): Wireless communication is possible by receiving signals through superheterodyne receivers.

49. Assertion (A): The LED is a light emitting diode, that gives out spontaneous emissions, when it is energized.
Reason (R): The recombination of holes and electrons in semiconductor materials gives off energy in terms of light and heat.

50. Assertion (A): Power is integration of energy over a period of time.
Reason (R): The accuracy of power measurement is dependent on integration time constant.

51. Arrange the following in the increasing order of their forbidden energy gap:
I. Conductors
II. Insulators
III. Germanium
IV. Silicon
(A) I, II, III, IV
(B) I, II, IV, III
(C) I, III, IV, II
(D) I, IV, III,II

52. The correct order in which time domain response is obtained for a network
I. Laplace transform
II. Differential equation
III. Time domain response
IV. Network
(A) I, II, III, IV
(B) II, III, IV, I
(C) III, IV, II, I
(D) IV, II, I, III

53. The correct start to end sections of a regulator circuit are
I. Filtering
II. Protection
III. Rectification
IV. Regulation
(A) II, I, III, IV
(B) III, II, IV, I
(C) I, III, IV, II
(D) IV, II, I, III

54. Arrange the following logic families in the decreasing order of their propagation delay:
I. CMOS
II. TTL
III. ECL
IV. DTL
(A) II, III, IV, I
(B) IV, II, III, I
(C) III, I, II, IV
(D) I, IV, II, III

55. The interrupts in 8085 processor are
I. RST 6.5
II. RST 5.5
III. TRAP
IV. RST 0
Keep the sequence from least priority to highest priority.
(A) III, I, II, IV
(B) IV, I, II, III
(C) IV, II, I, III (D) III, IV, II, I

56. The correct sequence to write a loop statement is formed
I. body
II. main( )
III. test condition
IV. initialization
(A) I, IV, II, III
(B) IV, III, I, II
(C) III, II, IV, I
(D) II, IV, III, I

57. The following frequency bands are used in microwaves:
I. Ku band
II. Ka band
III. L band
IV. C band
The correct sequence in decreasing frequency is by:
(A) II, III, IV, I
(B) I, II, III, IV
(C) II, I, III, IV
(D) II, I, IV, III

58. Consider the following communication systems:
I. Microwave communication system
II. Optical communication system
The correct sequence of these systems from the point of view of increasing order of bandwidth is
(A) II, I, IV, III
(B) I, II, III, IV
(C) III, IV, II, I
(D) IV, III, I, II

59. The following are the fibers used in optical communication systems:
I. Plastic fibers
III. Glass fibers operating at 1330 nm
IV. Glass fibers operating at 1550 nm
The correct sequence of attenuation of the above fibers in increasing order are:
(A) I, II, III, IV
(B) IV, III, II, I
(C) II, I, IV, III
(D) IV, II, I, III

60. Arrange the steps given below in correct order:
I. Network function
II. Change of sign
III. Stability
IV. Routh array
The order in which the stability is evaluated using Routh criterion:
(A) I, III, II, IV
(B) I, IV, II, III
(C) IV, I, III, II
(D) III, II, I, IV

61. Match the given list of devices with their respective application :
List-I                                                   List-II
(a) Diode                                             (i) Rectification
(b) Tunnel diode                                 (ii) Microwave switching
(c) Zener diode                                   (iii) Oscillator
(d) PIN diode                                                 (iv) Voltage regulator
Codes :
(a) (b) (c) (d)
(A) (i) (iii) (iv) (ii)
(B) (i) (iv) (iii) (ii)
(C) (i) (ii) (iii) (iv)
(D) (i) (iv) (ii) (iii)

62. Match List – I with List – II and select the correct answer using codes given below:
List-I                                                               List-II
(a) Voltage source in a branchwww.netugc.in                        (i) Polar capacitor
(b) Hysteresis                                                  (ii) Super node
(c) Non-bilateral                                              (iii) h-parameters
(d) Transistor small signal model                    (iv) Avoid false triggering
Codes:
(a) (b) (c) (d)
(A) (i) (iv) (iii) (ii)
(B) (iii) (i) (ii) (iv)
(C) (ii) (iv) (i) (iii)
(D) (iv) (ii) (iii) (i)

63. Match List – I with List – II and select the correct answer using codes given below:
List-I                                                                           List-II
(a) Gating pulse                                                           (i) BJT
(b) Series pass element                                                (ii) Monostable multivibrator
(c) Lock range                                                             (iii) Voltage regulator
(d) Base width modulation                                         (iv) PLL
Codes:
(a) (b) (c) (d)
(A) (i) (ii) (iv) (iii)
(B) (ii) (iii) (iv) (i)
(C) (iii) (iv) (i) (ii)
(D) (iv) (ii) (iii) (i)

64. Match the following list:
List-I                                                               List-II
(a) Positive OR                                               (i) Negative NAND
(b) Positive AND                                            (ii) Negative AND
(c) Positive NOR                                            (iii) Negative OR
(d) Positive NAND                                         (iv) Negative NOR
Codes:
(a) (b) (c) (d)
(A) (iii) (ii) (i) (iv)
(B) (i) (iv) (ii) (iii)
(C) (ii) (i) (iii) (iv)
(D) (ii) (iii) (i) (iv)

65. Match the following:
List-I                                                               List-II
(a) MOV A, B                                                 (i) Logical instruction
(b) JNC =address                                            (ii) Arithmetic instruction
(c) OR A, B                                                    (iii) Data transfer
(d) ADD A, H                                                (iv) Branching  instruction
Codes:
(a) (b) (c) (d)
(A) (ii) (iii) (i) (iv)
(B) (iii) (iv) (i) (ii)
(C) (iv) (iii) (ii) (i)
(D) (iv) (i) (iii) (ii)

66. Match List – I with List – II and select the correct answer using codes given below:
List-I                                                                           List-II
(a) call by reference                                                     (i) Incorrect statement
(b) size of (float);                                                        (ii) Function
(c) &                                                                            (iii) 4
(d) return (a, b);                                                           (iv) bitwise AND
Codes:
(a) (b) (c) (d)
(A) (i) (ii) (iii) (iv)
(B) (iv) (iii) (ii) (i)
(C) (ii) (iii) (iv) (i)
(D) (iii) (iv) (i) (ii)

67. Match List – I with List – II and select the correct answer using the codes given below:
List-I                                                               List-II
(a) Ferrite devices                                           (i) Oscillator
(b) Magnetron                                                 (ii) Bunching
(c) Klystron                                                     (iii) Cross field devices
(d) Gun-diode                                                 (iv) Circulators
Codes:
(a) (b) (c) (d)
(A) (iv) (ii) (i) (iii)
(B) (iv) (iii) (ii) (i)
(C) (iii) (iv) (ii) (i)
(D) (i) (ii) (iii) (iv)

68. Match the following:
List-I                                                   List-II
(a) Digital Filters                                 (i) More channels are =accommodated
(b) Signal Processing                           (ii) Slow speed of data transfer
(c) Time Division Mulplexing (iii) Hardware techniques
(d) Frequency Division Multiplexing  (iv) Software Btechniques
Codes :
(a) (b) (c) (d)
(A) (iv) (iii) (ii) (i)
(B) (i) (ii) (iii) (iv)
(C) (iii) (iv) (i) (ii)
(D) (iv) (iii) (i) (ii)

69. Match List – I with List – II and select the correct answer using the codes given below:
List-I                                                               List-II
(a) Fan regulator                                              (i) Two transistor model
(b) SCR                                                           (ii) dc-dc conversion
(c) Choppers                                                    (iii) Triac-Diac pair
(d) Quantum efficiency                                  (iv) LED
Codes :
(a) (b) (c) (d)
(A) (ii) (iii) (iv) (i)
(B) (iv) (iii) (i) (ii)
(C) (iii) (i) (ii) (iv)
(D) (iii) (ii) (i) (iv)

70. Match the following :
List-I                                                               List-II
(a) Small displacement                                    (i) DSO
(b) Phase measurement                                   (ii) X-ray diffractometer
(c) Slowly varying signals                               (iii) CRO
(d) Crystal structure                                        (iv) LVDT
Codes :
(a) (b) (c) (d)
(A) (iv) (iii) (i) (ii)
(B) (iii) (ii) (iv) (i)
(C) (ii) (i) (iii) (iv)
(D) (i) (iv) (ii) (iii)

An operational amplifier is a direct coupled high gain amplifier with feedback. It is employed to perform a wide variety of functions such as summer, integrator, differentiator, logarithmic amplifier, oscillators, filters, comparators voltage to frequency converter, amplitude modulators, sample and hold circuit and so on.
An ideal Op-Amp has infinite input =resistance, zero output resistance, infinite voltage gain and bandwidth, zero offset and no drift. An ideal Op-Amp is a perfectly balanced circuit such that output voltage is zero for two equal input signals. However a real Op-Amp exhibits imbalance due to mismatch at the input differential stage. It gives rise to offsets. In practical applications offsets are removed using balancing networks. In general an Op-Amp consists of the following four stages:
(1) Differential amplifier first stage
(2) Differential amplifier second stage
(3) Emitter follower
(4) Level translator and output stage It is most widely used analog device.

71. Which is a non-linear application?
(A) I-V converter
(B) Sample-and-hold
(C) Voltage follower
(D) Active filter

72. Analog multiplication is carried out with
(A) Scalar
(B) Precision rectifier
(C) Sample-and-hold circuit
(D) Logarithmic amplifier

73. Very high input resistance differential stages are used in Op-Amp
(A) To minimise input offset voltage
(B) To minimise output offset voltage
(C) To minimise input offset current
(D) To minimise output offset current

74. If VDC = 5V is applied to the input of a differentiator circuit its output will be
(A) Zero
(B) Square pulse
(C) Ramp
(D) 5 V