2013 June UGC NET Solved Question Paper in Electronic Science, Paper III

1. Semiconductor materials are made up of

(A) Metallic bond

(B) Ionic bond

(C) Vander Waal’s bond

(D) Covalent bond

Answer: (D)

 

2. A UJT has

(A) Negative resistance characteristics

(B) Low firing current

(C) Bipolar device

(D) Relax indefinitely

Answer: (A)

 

3. The current in a zener diode is controlled by

(A) zener diode resistance

(B) Potential barrier

(C) Impact ionization

(D) External circuits resistance

Answer: (D)

 

4. The ripple factor of a half-wave rectifier is found to be

(A) 1.57

(B) 1.21

(C) 1.12

(D) 1.41

Answer: (B)

 

5. Hartley oscillator is commonly used in

(A) Radio receivers

(B) Radio transmitters

(C) TV receivers

(D) Microwave transmitters

Answer: (A)

 

6. The multiplexer is also known as

(A) Counter

(B) Decoder

(C) Shift register

(D) Data selector

Answer: (D)

 

7. Quantizing Noise occurs in

(A) Time-division multiplexing

(B) Frequency-division multiplexingwww.netugc.com

(C) Pulse-Code modulation

(D) Pulse width modulation

Answer: (C)

 

8. CMRR (Common Mode Rejection Ratio) for a differential amplifier should be

(A) Zero

(B) Unity

(C) Small

(D) Large

Answer: (D)

 

9. An ideal op-amp has

(A) Infinite common mode gain as well as differential gain.

(B) Infinite common mode gain and zero differential gain.

(C) Infinite differential gain and zero common mode gain.

(D) Zero differential gain and infinite common mode gain.

Answer: (C)

 

10. In 8085, example for Non-maskable interrupts is

(A) Trap

(B) RST 6.5

(C) INTR

(D) RSTO

Answer: (A)

11. The pH is a measure of

(A) Acidity

(B) Density

(C) Specific density

(D) Solubility

Answer: (A)

 

12. To separate channels in an FDM receiver, it is necessary to use

(A) Integration

(B) Band pass filter

(C) Differentiation

(D) AND gates

Answer: (B)

 

13. Time-Division Multiplex

(A) Can be used with PAM only

(B) Combines five groups into a super group

(C) Stacks 24 channels in adjacent frequency slots

(D) Interleaves pulses in time domain belonging to different transmissions

Answer: (D)

 

14. In Half Duplex (HDX), data transmission is possible

(A) In one direction

(B) In both direction

(C) In both direction, but not at the same time

(D) In both direction simultaneously

Answer: (C)

 

15. Indicate which of the following system is digital?

(A) Pulse – Position Modulation

(B) Pulse – Code Modulation

(C) Pulse – Width Modulation

(D) Pulse – Amplitude Modulation

Answer: (B)

 

16. The value of Numerical Aperture in optical fibre is

(A) Greater than 1

(B) Less than 1

(C) Equal to 1

(D) Equal to ∞

Answer: (B)

 

17. The Refractive Index of core in optical fibre should be

(A) Smaller than R.I. of cladding

(B) greater than R.I. of cladding

(C) Equal to R.I. of cladding

(D) Equal to air

Answer: (B)

 

18. SCR turns off from conducting state to blocking state on

(A) Reducing gate current

(B) Reversing gate current

(C) Reducing anode current below holding current value

(D) Applying ac to the gate

Answer: (C)

 

19. The balanced modulator essentially is

(A) An oscillator

(B) A mixer

(C) A product modulator

(D) An amplifier

Answer: (C)

 

20. Which semiconductor device acts like a diode and two resistors?

(A) UJT

(B) SCR

(C) Diac

(D) Triac

Answer: (A)

21. Which type of analogue-to-digital converter is often used in digital voltmeter?

(A) Single slope A/D converter

(B) Dual slope A/D converter

(C) Successive approximation method

(D) Flash converter

Answer: (B)

 

22. Which of the following logic family is fastest of all?

(A) TTL

(B) RTL

(C) DCTL

(D) ECL

Answer: (D)

 

23. Photoconductive devices are made of

(A) Radioactive materials

(B) Highly conductive materials

(C) Semiconductor materials

(D) Highly insulating materials

Answer: (C)

 

24. The unit of mobility of semiconductor is

(A) m2 v–1 s–1

(B) m v–1 s–1

(C) v s m–1

(D) v m s–1

Answer: (A)

 

25. The figure of merit of logic family is given by

(A) Gain bandwidth product

(B) (Propagation delay time) × (power dissipation)

(C) (Fan out) × (propagation delay time)

(D) (Noise margin) × (power dissipation)

Answer: (B)

 

26. In a 8085 microprocessor, the resistor which holds address of the next instruction to be fetched is

(A) Accumulator

(B) Program counter

(C) Stack pointer

(D) Instructor Register

Answer: (B)

 

27. If a carrier modulated by a digital bit stream had one of the possible phases of 0, 90, 180 and 270 degrees then modulation is called

(A) BPSK

(B) FSK

(C) QPSK

(D) QAM

Answer: (C)

 

28. The logic gate normally used to get the carry bit in a half adder is

(A) AND

(B) EX-OR

(C) NOT

(D) OR

Answer: (A)

 

29. A counter in which all the flip-flops receive the clock pulse at the same time is known as

(A) Ripple counter

(B) Synchronous counter

(C) Clocked counter

(D) Asynchronous counter

Answer: (B)

 

30. Which of the following devices is suitable for very low power oscillator circuits only?

(A) TRAPATT diode

(B) IMPATT diode

(C) Gunn diode

(D) Tunnel diode

Answer: (D)

 

31. Thyristors can be turned off by

1. Reducing the current below the holding current value

2. Applying a negative voltage to the anode of the device

3. Reducing the gate current

Of these statements:

Codes:

(A) 1 & 2 are correct.

(B) 1 & 3 are correct.

(C) 2 & 3 are correct.

(D) 1, 2 & 3 are correct.

Answer: (A)

 

32. The 555 timer can be employed in

1. A monostable multivibrator

2. A bistable multivibratorwww.netugc.com

3. An astable multivibrator

Of these statements

Codes:

(A) 1 & 2 are correct.

(B) 1 & 3 are correct.

(C) 2 & 3 are correct.

(D) 1, 2 & 3 are correct.

Answer: (B)

 

33. When a plane wave propagating through free space, the direction of the field

1. ‘E’ is perpendicular to the direction of propagation.

2. ‘H’ is perpendicular to the direction of propagation.

3. ‘E’ is perpendicular to the direction of the field ‘H’.

Codes:

(A) 1 & 2

(B) 2 & 3

(C) 1 & 3

(D) 1, 2 & 3

Answer: (D)

 

34. Consider the following statements regarding a semiconductor:

1. Acceptor level lies close to the valence band.

2. Donor level close to the valence band.

3. n-type semiconductor behaves as a conductor at zero Kelvin.

4. p-type semiconductor behaves as a insulator at zero Kelvin.

Codes:

(A) 2 & 3 are correct.

(B) 1 & 3 are correct.

(C) 1 & 4 are correct.

(D) 3 & 4 are correct.

Answer: (C)

 

35. A transducer converts

1. A potential difference is developed across a current carrying metal strip when the strip is placed in transverse magnetic field.

2. The Hall Effect is very weak in metals but large in semiconductors.

3. The Hall Effect is very weak in semiconductors but is large in metals.

4. It is applied in the measurement of the magnetic field intensity.

Codes:

(A) 1, 2 & 3 only

(B) 2 & 4 only

(C) 1, 3 & 4 only

(D) 1, 2 & 4 only

Answer: (D)

 

36. Consider the following statements:

1. Race around condition occurs in a JK flip-flop when both the inputs are one.

2. A flip-flop is used to store one bit of information.

3. A transparent latch consists in D-type in flip-flop.

4. Master-Slave configuration is used in flip-flop to store two bits of information.

Which of these statements are correct?

Codes:

(A) 1, 2 & 3 only

(B) 1, 3 & 4 only

(C) 1, 2 & 4 only

(D) 2, 3 & 4 only

Answer: (A)

 

37. Consider the following:

1. Oscillator

2. Emitter follower

3. Cascaded amplifier

4. Power amplifier

Which of these use feedback amplifiers?

(A) 1 & 2

(B) 1 & 3

(C) 2 & 4

(D) 3 & 4

Answer: (A)

 

38. Consider the following statements, regarding an Op-Amp:

1. All types of negative feedback reduce nonlinear distortion.

2. All types of negative feedback reduce the output offset voltage.

3. Non-inverting (current and voltage) feedback increases the input impedance.

4. Inverting (current and voltage) feedback decreases input impedance.

Codes:

(A) 1 only

(B) 2 & 3 only

(C) 2 & 4 only

(D) 1, 2, 3 & 4 only

Answer: (D)

 

39. If an electric field is applied to an n-type semiconductor bar, the electrons and holes move 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 currents.

Which of these statements is/are correct?

(A) 1 & 3

(B) 1 & 2

(C) 2 & 3

(D) 3 alone

Answer: (B)

 

40. A digital multiplexer can be used for which of the following?

1. Parallel-to-serial conversion

2. Many-to-one switch

3. To generate memory chip select

4. for code conversion

Select the correct answer using the code given below:

Codes:

(A) 1, 3 & 4

(B) 2, 3 & 4

(C) 1 & 2

(D) 2 & 3

Answer: (C)

 

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): In Intel 8085, the lower byte of address and data are multiplexed.

Reason (R): This helps not to limit the number of external pin terminals.

Answer: (C)

 

42. Assertion (A): In an Op-Amp circuit when one input terminal of the Op-Amp is grounded, the other terminal becomes a virtual ground.

Reason (R): Input impedance of the Op-Amp is high.

Answer: (B)

 

43. Assertion (A): The intrinsic Fermi level of a semiconductor lies exactly at the middle of the energy gap.

Reason (R): The densities of the available state in valence and conduction bands of a semiconductor are equal.

Answer: (A)

 

44. Assertion (A): The top down structured programming should be used for developing programs.

Reason (R): The top down structured programming methodology enables us to get readable and easily provable programs.

Answer: (B)

 

45. Assertion (A): A processor can reference a memory stack without specifying an address.

Reason (R): The address is always available and automatically updated in the stack pointer.

Answer: (A)

 

46. Assertion (A): In optical fibre communication, light rays are guided by the total internal reflection at the interface between fibre core and cladding.

Reason (R): The Refractive Index of core is large than the Refractive Index of cladding.

Answer: (A)

 

47. Assertion (A): Tunnel diode represents negative resistance characteristics and when operated in this region may be used as an oscillator.

Reason (R): Tunnel diode is heavily doped p-n junction having an extremely narrow junction which electrons are able to tunnel through it.

Answer: (A)

 

48. Assertion (A): The part of root locus on the real axis is not dependent upon the poles and zeros which are not on the real axis.

Reason (R): Poles and zeros which are not on the real axis always occur in conjugate pairs.

Answer: (A)

 

49. Assertion (A): A programmable Read-Only-Memory can be used as a synchronous counter.

Reason (R): Each memory location of a programmable Read-Only- Memory is programmed and can be read synchronously.

Answer: (C)

 

50. Assertion (A): A half-adder is faster than full-adder.

Reason (R): A half-adder gives only one output while a full adder gives two outputs.

Answer: (C)

 

51. Consider the following circuit configurations:

1. Common emitter

2. Common base

3. Emitter follower

4. Emitter follower using Darlington pairs

The correct sequence in increasing order of the input resistances of these configurations is

(A) 2, 1, 4, 3

(B) 1, 2, 4, 3

(C) 2, 1, 3, 4

(D) 1, 2, 3, 4

Answer: (C)

 

52. Consider the Analogue and Digital converters given below:

1. Successive Approximation ADC

2. Dual Ramp ADC

3. Counter Method ADC

4. Simultaneous ADC

The correct sequence of the ascending order in terms of conversion times of these ADC’s is

(A) 3, 2, 4, 1

(B) 2, 3, 4, 1

(C) 2, 3, 1, 4

(D) 3, 2, 1, 4

Answer: (Wrong question)

 

53. Arrange the following in order of decreasing frequency:

1. C band

2. X band

3. Ku band

4. K band

Codes:

(A) 1, 2, 3, 4

(B) 2, 3, 4, 1

(C) 1, 4, 3, 2

(D) 4, 3, 2, 1

Answer: (D)

 

54. Consider the following cables:

1. Single mode optical fibre cable

2. Multimode optical fibre cable

3. Graded-index optical fibre cable

4. Co-axial cable

The correct sequence in increasing order of data rate is

(A) 1, 2, 3, 4

(B) 4, 2, 3, 1

(C) 1, 2, 4, 3

(D) 4, 3, 2, 1

Answer: (B)

 

55. The interrupts in 8085 processor are

1. RST 7.5

2. RST 6.5

3. RST 5.5

4. TRAP

Keep the sequence from least priority to highest priority

(A) 1, 2, 3, 4

(B) 4, 3, 2, 1

(C) 3, 2, 1, 4

(D) 1, 4, 3, 2

Answer: (C)

 

56. Consider the following frequency spectrum of the electro-magnetic wave:

1. FM radio waves

2. Microwaves

3. Visible range

4. X-ray

Write down the frequency spectrum in ascending order

(A) 4, 3, 2, 1

(B) 1, 3, 2, 4

(C) 3, 2, 4, 1

(D) 1, 2, 3, 4

Answer: (D)

 

57. Consider the following logic families:

1. MOS

2. TTL

3. RTL

4. ECL

The sequence of these logic families in the order of their increasing propagation delay is

(A) 1, 2, 3, 4

(B) 4, 2, 3, 1

(C) 2, 1, 3, 4

(D) 4, 3, 2, 1

Answer: (B)

 

58. Consider the following steps:

1. Etching

2. Exposure to UV radiation

3. Stripping

4. Developing

After a wafer has been coated with photo-resist, the correct sequence of these steps in photolithography is

(A) 1, 4, 2, 3

(B) 2, 4, 1, 3

(C) 2, 1, 3, 4

(D) 1, 3, 2, 4

Answer: (B)

 

59. The following microprocessor operations are part of interrupt cycle of a control unit:

1. MAR ← Save-address

2. PC ← Routine-address

3. MBR ← (PC)

4. Memory ← MBR

Which of the following is the correct order of their occurrence?

(A) 1, 2, 3

(B) 3, 4, 2

(C) 2, 3, 4

(D) 4, 3, 1

Answer: (A)

 

60. Consider the following logic families:

1. RTL

2. DTL

3. TTL

4. ECL

The sequence of these logic families in the order of their decreasing Fan-Out is

(A) 1, 2, 3, 4

(B) 2, 1, 3, 4

(C) 4, 3, 2, 1

(D) 3, 4, 2, 1

Answer: (C)

 

61. List – I                  List – II

a. BJT                          i. Pinch off effect

b. FET                         ii. Controlled rectification

c. SCR                         iii. Negative Resistance Characteristics

d. Tunnel diode           iv. Punch through effect

Codes:

       a b c d

(A) i iii ii iv

(B) i ii iii iv

(C) iv i ii iii

(D) i iv iii ii

Answer: (C)

 

62. List – I                                                                  List – II

a. Frequency modulation                                            i. Envelope detection

b. Double sideband suppressed signal carrier             ii. Companding

c. PCM                                                                        iii. Balance modulator

d. Amplitude modulation                                           iv. Pre-emphasis and de-emphasis

Codes:

      a b c d

(A) i ii iii iv

(B) ii iii i iv

(C) iii i ii iv

(D) iv iii ii i

Answer: (D)

 

63. List – I                                          List – II

a. Astable multivibrator                      i. Two-stable states

b. Bistable multivibrator                     ii. Free running oscillator

c. Monostable multivibrator                iii. One-stable state

d. Schmitt triggers                              iv. Square wave generator

Codes:

      a b c d

(A) i iii iv ii

(B) iii iv i ii

(C) ii i iii iv

(D) ii i iv iii

Answer: (C)

 

64. List – I                  List – II

a. Gunn diode                         i. Junction less device

b. Solar cell                 ii. Single junction device

c. MOSFET                 iii. Triple junction device

d. SCR                        iv. Double junction device

Codes:

       a b c d

(A) i iii ii iv

(B) i ii iv iii

(C) ii iv iii i

(D) i iii iv ii

Answer: (B)

 

65. List – I                              List – II

a. Capacitive transducer          i. Pressure

b. Thermocouple                     ii. Torque

c. Load cell                             iii. Displacement

d. Diaphragm                          iv. Temperature

Codes:

       a b c d

(A) ii iv iii i

(B) iii i ii iv

(C) ii i iii iv

(D) iii iv ii i

Answer: (D)

 

66. List – I                              List – II

a. Ampere’s law                      i. Force on a charge

b. Biot’s law                            ii. Force due to a current carrying conductor

c. Coulomb’s law                    iii. Electric flux density at a point

d. Gauss’s law                         iv. Magnetic flux density at a point

Codes:

       a b c d

(A) iii ii i iv

(B) iv ii i iii

(C) iv i ii iii

(D) iii i ii iv

Answer: (B)

 

67. List – I                                          List – II

a. Immediate addressing                     i. LDA 30 FF

b. Implied addressing                                     ii. MOV A, B

c. Register addressing                         iii. LXI H, 2050

d. Direct addressing                            iv. RRC

Codes:

       a b c d

(A) iii iv ii i

(B) ii i iii iv

(C) iii i ii iv

(D) ii iv iii i

Answer: (A)

 

68. List – I                              List – II

a. Simplex                               i. Bidirectional at same time but not between same two points

b. Half Duplex (HDX)            ii. Bidirectional and at same time between same two points

c. Full Duplex (FDX)              iii. Bidirectional but not at same time

d. Full/Full Duplex (F/FDX)   iv. Unidirectional

Codes:

       a b c d

(A) iv iii ii i

(B) iii ii i iv

(C) i ii iii iv

(D) ii iii iv i

Answer: (A)

 

69. List – I                              List – II

a. Drift current                        i. Law of Conservation of Charge

b. Einstein’s equation              ii. Electric field

c. Diffusion current                 iii. Thermal voltage

d. Continuity equation            iv. Concentration gradient

Codes:

       a b c d

(A) ii i iv iii

(B) iv iii ii i

(C) i ii iii iv

(D) iv ii iii i

Answer: (A)

 

70. List – I                  List – II

a. PN Diode                i. Oscillator

b. LED                        ii. Light emitter

c. PIN Diode               iii. Rectifier diode

d. Tunnel diode           iv. Light detector

Codes:

      a b c d

(A) i ii iii iv

(B) ii iii i iv

(C) iii ii iv i

(D) ii iv iii i

Answer: (C)

 

Read the paragraph and answer the questions to 71 – 75:

Multiplexing is the sending of separate signals together, over the same cable or bearer simultaneously without interference. Time division multiplex is a method of interleaving in the time domain pulses belonging to different transmissions. These pulses are generally narrow and separation between successive pulses is rather wide. That being the case it is possible, provided the two ends of a link are synchronized, to use the wide spaces for pulses belonging to other transmissions. Frequency division multiplexing concerns itself with combining continuous signals. It may be thought of as an outgrowth of independent side band transmission on a much enlarged scale. As will see 12 or 16 channels are combined into a group, 5 groups into a subgroup. Each group and subgroup is then sent as a whole unit one microwave link cable or other broadband system. Continental broadband systems are then treated followed by coaxial cables, fibre optic cable, microwave links and trope scatter systems.

 

71. A scheme in which several channels are interleaved and then transmitted together is known as

(A) frequency-division multiplex

(B) time-division multiplex

(C) A group

(D) A subgroup

Answer: (A)

 

72. Microwave link repeaters are typically 50 km apart

(A) Because of atmospheric attenuation

(B) Because of output tube power limitations

(C) Because of earths curvaturewww.netugc.com

(D) To ensure that the applied dc voltage is not excessive

Answer: (C)

 

73. Time-division multiplex

(A) Can be used with CPM only

(B) Combines five group into a super group

(C)Stacks 24 channels in adjacent frequency slots

(D) Interleaves pulses belonging to different transmissions

Answer: (D)

 

74. Broad band long distance communication was originally made possible by the advent of

(A) Geostationary satellite

(B) Repeater amplifier

(C) H.F. Radio

(D) Telegraph Cable

Answer: (B)

 

75. The number of repeaters along a co-axial cable link depends on

(A) Whether separate tubes are used for the two directions of transmission.

(B) The bandwidth of the system.

(C) The number of co-axial cables in the tube.

(D) The separation of equalizers.

Answer: (B)

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