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

1. In intrinsic semiconductor

(A) The electron density is twice the whole density

(B) The electron density is thrice the whole density

(C) The electron density is square root of the whole density

(D) The electron density is same as the whole density

Answer: (D)

 

2. PN junction diode can be used as a/an

(A) Oscillator

(B) Amplifier

(C) Insulator

(D) Rectifier

Answer: (D)

 

3. Norton’s equivalent form in any complex impedance circuit consists of

(A) An equivalent current source in parallel with an equivalent resistance.

(B) An equivalent voltage source in series with an equivalent resistance.

(C) An equivalent current source in parallel with equivalent impedance.

(D) An equivalent voltage source in series with equivalent impedance.

Answer: (C)

 

4. Zener diode is a

(A) Reverse biased diode

(B) Variable voltage source

(C) Constant current source

(D) Forward biased diode

Answer: (A)

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5. Which of the following oscillator make use of both positive and negative feedbacks?

(A) Hartley oscillator

(B) Colpit’s oscillator

(C) Phase shift oscillator

(D) Wein-Bridge oscillator

Answer: (D)

 

6. Superposition theorem can be applied only to circuits having

(A) Resistive elements

(B) Passive elements

(C) no-linear elements

(D) Linear bilateral elements

Answer: (D)

 

7. Identify the fastest analogue to digital converter

(A) Ramp conversion

(B) Parallel conversion

(C) Successive approximation

(D) Dual-slope integration

Answer: (B)

 

8. 1 K memory device contain

(A) 1064 memory cells

(B) 1024 memory cells

(C) 512 memory cells

(D) 640 memory cells

Answer: (B)

 

9. Which logic function has the output low only when both inputs are high?

(A) NOR

(B) OR

(C) AND

(D) NAND

Answer: (D)

 

10. In FM, when frequency deviation doubled, then

(A) Modulation Index is decreased

(B) Modulation Index is doubled

(C) Modulation Index halved

(D) No change occurs in modulation index values

Answer: (B)

11. Out of the following memory types, one that is volatile is

(A) Magnetic disc

(B) Ferrite core

(C) Semiconductor ROM

(D) Semiconductor RAM

Answer: (D)

 

12. An SCR can be formed by using

(A) 2 npn transistors

(B) 2 pnp transistors

(C) 1 npn and 1 pnp transistor

(D) 2 pn diode

Answer: (C)

 

13. The pH of human blood is between

(A) 6.5 to 7

(B) 7.5 to 8

(C) 8 to 9

(D) 4.5 to 5

Answer: (B)

 

14. What is SIM?

(A) Select Interrupt Mask

(B) Sorting Interrupt Mask

(C) Set Interrupt Mask

(D) Start Instruction Mode

Answer: (C)

 

15. Quantization noise occurs in

(A) TDM

(B) PCM

(C) FDM

(D) WDM

Answer: (B)

 

16. Which antenna gets circularly polarized?

(A) Yagi-Uda

(B) Dipole

(C) Parabolic www.netugc.com

(D) Helical

Answer: (D)

 

17. VSWR (Voltage Standing Wave Ratio) is always

(A) More than 1

(B) Less than 1

(C) 1

(D) 0.4

Answer: (A)

 

18. The ladder network used in D/A converter is

(A) Weighted resistance ladder

(B) R – R ladder

(C) R – 2R ladder

(D) R – C ladder

Answer: (C)

 

19. Latch is a

(A) T flip-flop

(B) Master-slave JK flip-flop

(C) D flip-flop

(D) JK flip-flop

Answer: (C)

 

20. In LED, light is emitted, because

(A) Diode emits light when gets heated.

(B) Recombination of charge carrier takes place.

(C) Light is made to reflect due to lens action.

(D) LED amplifies the light falling on it.

Answer: (B)

Directions (Q. Nos. 21 to 30): 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.

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 correct explanationof (A).

(C) (A) is true, but (R) is false.

(D) (A) is false, but (R) is true.

 

21. Assertion (A): 8421 code is weighted code.

Reason (R): 8421 code is self-complementary.

Answer: (C)

 

22. Assertion (A): A stack is a type of non-sequential access memory system.

Reason (R): Memory stacks help in keeping track of return addresses and saving data for subroutines.

Answer: (D)

 

23. Assertion (A): TEM waves exist in a waveguide.

Reason (R): Phase velocity and wave impedance for TEM waves are independent of the frequency of the waves.

Answer: (D)

 

24. Assertion (A): In FSK, a binary 1 usually produces a higher carrier frequency than a binary 0.

Reason (R): FSK maintains a constant amplitude carrier.

Answer: (B)

 

25. Assertion (A): An LTI discrete system represented by the difference equation y(n + 2) – 5y (n + 1) + 6y(n) = x(n) is unstable.

Reason (R): A system is unstable if the roots of the characteristic equation lie outside the unit circle.

Answer: (A)

 

26. Assertion (A): Stimulated emission is the key to the operation of LASER.

Reason (R): An important property of LASER radiation is its coherence, under which is meant the correlation between the phases of oscillation at different positions in space and at various moments of time.

Answer: (A)

 

27. Assertion (A): R-2R ladder type D/A converter has a higher speed of conversion than a weighted resistance D/A converter.

Reason (R): R–2R ladder type converter uses a smaller number of components than the weighted resistance D/A converter.

Answer: (C)

 

28. Assertion (A): UJT is used in relaxation oscillators.

Reason (R): UJT has negative resistance region in its characteristics.

Answer: (A)

 

29. Assertion (A): The race hazard problem does not occur in combinational circuits.

Reason (R): The output of a combinational circuit depends upon present inputs only.

Answer: (A)

 

30. Assertion (A): Digital communication needs some synchronisation signals.

Reason (R): ‘bit syn’ signal isrequired in time divisionmultiplexing to distinguishgroups of data.

Answer: (B)

 

31. Consider the following logic families:

1. MOS

2. TTL

3. RTL

4. ECL

The correct sequence of the logic families in the order of their increasing noise margin is

(A) 3, 4, 1, 2

(B) 3, 4, 2, 1

(C) 4, 3, 2, 1

(D) 4, 3, 1, 2

Answer: (B)

 

32. Which is the correct sequence in the generation of PCM?

1. Sampling

2. Converting to PAM

3. Quantization

4. Adding of supervisory signal

5. Encoding

(A) 1, 2, 5, 3, 4

(B) 1, 5, 2, 3, 4

(C) 1, 2, 3, 5, 4

(D) 4, 5, 1, 2, 3

Answer: (C)

 

33. Consider the following logic families:

1. MOS

2. CMOS

3. DTL

4. TTL

The correct sequence of power dissipation in increasing order is given by

(A) 2, 1, 3, 4

(B) 2, 1, 4, 3

(C) 1, 2, 3, 4

(D) 1, 2, 4, 3

Answer: (A)

 

34. The data can be transmitted by following means:

1. Coaxial cables

2. MMF

3. SMF

4. Twisted wire cable

The correct sequence in the increasing order of Bandwidth is

(A) 2, 3, 1, 4

(B) 4, 1, 2, 3

(C) 4, 1, 3, 2

(D) 1, 4, 2, 3

Answer: (B)

 

35. Consider the following devices:

1. BJT in CB mode

2. BJT in CE mode

3. JFET

4. MOSFET

The correct sequence of these devices in increasing order of their impedance is

(A) 2, 1, 3, 4

(B) 2, 1, 4, 3

(C) 1, 2, 3, 4

(D) 1, 2, 4, 3

Answer: (C)

 

Match the following (Q. Nos. 36 – 45):

 

36. List – I                  List – II

a. SCR                         i. dc drive control

b. Triac                        ii. Induction motor control

c. Chopper                   iii. Unidirectional

d. Cycloconverter       iv. Bidirectional

Codes:

       a b c d

(A) iv iii i ii

(B) i ii iii iv

(C) iii iv i ii

(D) i iv ii iii

Answer: (C)

 

Answer: (A)

 

38. List – I                  List – II

a. Varistor                   i. nonlinear resistance

b. Varactor diode        ii. Nonlinear reactance

c. Gunn diode                         iii. Negative resistance

d. PIN diode               iv. Controllable impedance type

Codes:

      a b c d

(A) i ii iii iv

(B) ii iii iv i

(C) iii iv i ii

(D) iv i ii iii

Answer: (A)

 

39. List – I                  List – II

a. Klystron                  i. Cross-field device

b. Reflex Klystron      ii. Bunching

c. Magnetron               iii. Velocity modulation

d. Gunn diode                         iv. Negative resistancewww.netugc.com

Codes:

       a b c d

(A) ii iii i iv

(B) i ii iii iv

(C) iv i ii iii

(D) i ii iv iii

Answer: (A)

 

40. List – I                  List – II

a. LED                        i. Stimulated emission

b. LASER                   ii. Spontaneous emission

c. Solar Cell                 iii. Power generator

d. Photo diode            iv. Detector

Codes:

      a b c d

(A) i ii iii iv

(B) ii i iii iv

(C) iii iv i ii

(D) iv i ii iii

Answer: (B)

 

41. List – I      List – II

a. DAA           i. Program control instruction

b. LXI                         ii. Data movement instruction

c. RST             iii. Interrupt instruction

d. JMP             iv. Arithmetic instruction

Codes:

      a b c d

(A) i ii iii iv

(B) iv ii iii i

(C) iii iv i ii

(D) ii i iii iv

Answer: (B)

 

42. List – I      List – II

a. 8031            i. Multiplexer

b. 7490            ii. Demultiplexer

c. 74155          iii. Microcontroller

d. 74151          iv. Decade counter

Codes:

       a b c d

(A) iii iv ii i

(B) i ii iii iv

(C) ii iii iv i

(D) iii i ii iv

Answer: (A)

 

43. List – I                  List – II

a. Bourdon tube          i. Distance

b. Strain gauge            ii. Temperature

c. Thermistor               iii. Pressure

d. LVDT                     iv. Stress

Codes:

      a b c d

(A) i ii iii iv

(B) iii iv ii i

(C) ii iii iv i

(D) i iii ii iv

Answer: (B)

 

44. List – I                                                      List – II

(Types of ADC)                                              (Characteristics)

a. Parallel comparator (i.e. flash) type             i. integrating type

b. Successive approximation                           ii. Fastest converter

c. Dual slope                                                   iii. Conversion time is independent of the amplitude of the analogue signal

d. Counter type                                               iv. Uses DAC in feedback path

Codes:

       a b c d

(A) ii iii i iv

(B) i ii iv iii

(C) iv iii ii i

(D) iv ii iii i

Answer: (A)

 

45. List – I                                                      List – II

a. Flip-Flop can be used as latch                     i. D Flip-flop

b. Flip-Flop can be used as delayed                ii. Master- Slave

c. Flip-Flop does not have race problem         iii. JK

d. Flip-flop can be used as shift registers       iv. R-S

Codes:

      a b c d

(A) iv i ii iii

(B) ii iv i iii

(C) i iii ii iv

(D) iii i iv ii

Answer: (A)

 

Read the paragraph and answer the questions 46 to 50:

Microwave tubes are used as microwave amplifiers and oscillators. Three general type of microwaves tubes in which third type of tubes are useful. In this tube 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 counterpart is called Backward Wave Oscillator (BWO). Another group of tube in which a magnetic field ensures a constant electron beam – RF field interaction and this is complimented by the cross-field amplifier (CFA). Multi-cavity Klystron is used as an amplifier of microwaves and it consists of buncher cavity and cache cavity. The Reflex Klystron is a low power and low efficiency microwave oscillator. Reflex Klystron oscillator has been replaced by various semiconductor oscillators.

 

46. One of the following is unlikely to be used as pulsed device. It is the

(A) Multi-cavity Klystron

(B) BWO

(C) CFA

(D) TWT

Answer: (B)

 

47. One of the reason why vacuum tubes eventually fail at microwave frequencies is that their

(A) Noise figure increases

(B) Transit-time becomes too short

(C) Shunt capacitive reactance becomes too large

(D) Series inductive reactance become too small

Answer: (A)

 

48. The Multi-cavity Klystron

(A) Has a high repeller voltage to ensure a rapid transit time.

(B) Is not a good low-level amplifier because of noise.

(C) Is not suitable for pulsed operation.

(D) Needs a long transit time through the buncher cavity to ensure current modulation.

Answer: (B)

 

49. Indicate the false statement. Klystron amplifiers may use intermediate cavities to

(A) Increase the band width of the device

(B) Improve the power gain

(C) Increase the efficiency of the Klystron

(D) Prevent the oscillations that occur in two cavities Klystron

Answer: (D)

 

50. TWT is sometimes preferred to the multi-cavity Klystron amplifier because the former

(A) Is more efficient

(B) Has a greater band width

(C) Has a higher number of modes

(D) Produces a higher output power

Answer: (B)

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