# NTA UGC NET Electronic Science Paper 2 Solved Question Paper 2012 June

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## NTA UGC NET Electronic Science Paper 2 Solved Question Paper 2012 June

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1. In a JFET the change in drain current is due to the applied

(A) Electric field between S and D

(B) Electric field between G and S

(C) Magnetic field between S and D

(D) Magnetic field between G and S

2. The increase in temperature, the electrical conductivity would

(A) increase in metals as well as increase in semiconductors

(B) increase in metals but decrease in semiconductors

(C) decrease in metals but increase in semiconductors

(D) decrease in metals as well as in semiconductors

3. A network contains only independent current sources and resistors. If values of all resistors are doubled, then values of node voltages

(A) will become half

(B) will remain unchanged

(C) will become double

(D) cannot be determined unless circuit configuration and values of the resistors are known

4. Thevenin’s theorem replaces a complicated circuit facing a load by an

(A) ideal voltage source and parallel resistor

(B) ideal current source and parallel resistor

(C) ideal current source and series resistor

(D) ideal voltage source and series resistor

5. When Op-Amp is used as an integrator, the feedback element is

(A) Resistor

(B) Capacitor

(C) Zener diode

(D) Voltage divider

6.

7. How many Flip-Flops are required to build a binary counter circuit to count from 0 to 1023?

(A) 1

(B) 6

(C) 10

(D) 24

8. Among the following, the slowest ADC (Analog-to-digital converter) is

(A) Parallel-comparator (i.e.) flash type

(B) Successive approximation type

(C) Integrating type

(D) Counting type

9. In a microcomputer, WAIT states are used to

(A) make the processor wait during a DMA operation

(B) make the processor wait during a power interrupt processing

(C) make the processor wait during a power shut down

(D) interface slow peripherals to the processor

10. In a microprocessor, the register which holds the address of the next instruction to be fetched is

(A) Accumulator

(B) Program Counter

(C) Stack Pointer

(D) Instructor Register

11. Consider the following structure and declaration:

1. struct date {

2. int day;

3. int month;

4. int year;

5. };

Struct data *pd ;

Which of the following is the correct method to refer to the year member?

(A) (*pd)×year

(B) (*pd)*year

(C) (*pd)®year

(D) pd®year

12. Which of the following is not a linear data structure?

(A) Array

(C) Stack

(D) Tree

13.

14.

15. Time-Division Multiplexing

(A) can be used with PAM only.

(B) combines five groups into a supergroup.

(C) stacks 24 channels in adjacent frequency slots.

(D) interleaves pulses belonging to different transmissions.

16. One of the following types of noise becomes of great importance at high frequencies. It is the

(A) Shot noise

(B) Random noise

(C) Impulse noise

(D) Transit-time noise

17. A relaxation oscillator is one which

(A) oscillates continuously

(B) has two stable states

(C) relax indefinitely

(D) produces non-sinusoidal output

18. The transducer which generates electrical power

(A) Photoconductor

(B) Photodiode

(C) Solar cell

(D) Phototransistor

19. The step-index monomode fiber has diameter

(A) < 10 μm

(B) 50 μm

(C) 100 μm

(D) 200 μm

20. Which control system has hysteresis property?

(A) ON-OFF controller

(B) Proportional controller

(C) Integral controller

(D) P-I-D controller

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 explanation of (A).

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

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

21. Assertion (A) : If a semiconductor is placed in a transverse magnetic field B and an electric field E is applied across its other two faces, then it would produce an electric current I, in the direction perpendicular to both B and E.

Reason (R) : Hall co-efficient is proportional to the mobility of charge carrier in semi-conductor.

22. Assertion (A) : The voltage-current characteristic of tunnel diode exhibits dynamic negative resistance region.

Reason (R) : The negative resistance occurs, therefore, tunnel diode behaves as low power oscillating device.

23. 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 D/A converter uses a smaller number of components than the weighted resistance D/A converter.

24. 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.

25. 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.

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

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

27. 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.

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

29. 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.

30. Assertion (A) : In PCM a message signal is represented by a sequence of coded pulses, which is accomplished by representing the signal in discrete form in both time and amplitude.

Reason (R) : The signal encoded in the form of quantized samples which translates into a coded number.

31. Consider the following circuit configurations :

1. Common emitter

2. Common base

3. Emitter follower

4. Emitter follower using Dartington pair. 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

32. Digital measuring instruments use the following types of A to D converters :

1. Dual slope Type

2. Counter Type

3. Flash Type

The correct sequence for these converters in decreasing order of their speed (fastest to slowest) is

(A) 3, 1, 2

(B) 1, 2, 3

(C) 2, 3, 1

(D) 3, 2, 1

33. Consider the following logic families :

1. MOS

2. DTL

3. RTL

4. ECL

The 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, 1, 2

(D) 4, 3, 2, 1

34. Consider the following communication systems :

3. Microwave Communication

4. Optical Fiber Communication

The sequence of the communication systems in the order of their increasing carrier frequency is

(A) 4, 2, 1, 3

(B) 2, 1, 3, 4

(C) 1, 2, 3, 4

(D) 3, 4, 1, 2

35. The highest data rate can be transmitted using following cables :

1. Co-axial cable

2. Twisted-wire cable

3. Optical fiber cable The correct sequence in the increasing order is

(A) 1, 3, 2

(B) 3, 1, 2

(C) 2, 1, 3

(D) 3, 2, 1

36. Match List – I with List – II and select the correct answer using codes given below :

List – I                                    List – II

(a) LASER                              (i) Spontaneous emission

(b) Solar Cell                           (ii) Consumes electrical power due to the incident light

(c) Photo diode                       (iii) Delivers power to a load

(d) LED                                  (iv) Stimulated emission

Codes :

(a) (b) (c) (d)

(A) (iv) (iii) (i) (ii)

(B) (iii) (iv) (ii) (i)

(C) (iv) (iii) (ii) (i)

(D) (iii) (iv) (i) (ii)

37. 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)

38. 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)

39. List – I                                          List – II

(a) Parallel comparator                        (i) n-bits conversion time

(b) Successive approximation             (ii) Fastest converter

(c) Dual slope                                      (iii) Voltage dependent conversion type

(d) Counter type                                 (iv) Integrating type

Codes :

(a) (b) (c) (d)

(A) (ii) (i) (iii) (iv)

(B) (ii) (i) (iv) (iii)

(C) (i) (ii) (iv) (iii)

(D) (i) (ii) (iii) (iv)

40. 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 deemphasis

Codes :

(a) (b) (c) (d)

(A) (i) (ii) (iii) (iv)

(B) (i) (ii) (iv) (iii)

(C) (iv) (iii) (i) (ii)

(D) (iv) (iii) (ii) (i)

41. List – I                                                                  List – II

(a) LVDT                                                                    (i) Pressure

(b) Bourdon tube                                                        (ii) Temperature

(c) Strain gauge                                                           (iii) Displacement

(d) Thermistor                                                             (iv) Stress

Codes :

(a) (b) (c) (d)

(A) (iv) (iii) (ii) (i)

(B) (iii) (ii) (i) (iv)

(C) (iv) (i) (iii) (ii)

(D) (iii) (i) (iv) (ii)

42. List – I                                                      List – II

(Flags) (Bit Position)

(a) Sign flag                                                    (i) 4th bit

(b) Parity                                                         (ii) 6th bit

(c) Zero                                                           (iii) 2nd bit

(d) Auxiliary carry                                          (iv) 7th bit

Codes :

(a) (b) (c) (d)

(A) (i) (iii) (ii) (iv)

(B) (iv) (iii) (ii) (i)

(C) (i) (iv) (iii) (ii)

(D) (ii) (i) (iii) (iv)

43. List – I                                                      List – II

(a) Gunn diode                                                (i) Junction less device

(b) Solar cell                                                    (ii) Single junction device

(c) MOSFET                                                   (iii) Double junction device

(d) SCR                                                           (iv) Triple junction device

Codes :

(a) (b) (c) (d)

(A) (iv) (i) (ii) (iii)

(B) (iii) (iv) (i) (ii)

(C) (i) (ii) (iii) (iv)

(D) (ii) (iii) (i) (iv)

44. List – I                                                      List – II

(a) Monostable multivibrator                          (i) Quasi stable state

(b) Astable multivibrator                                 (ii) One stable state

(c) Schmitt trigger                                           (iii) Two stable state

(d) Bistable multivibrator                                (iv) No stable state

Codes :

(a) (b) (c) (d)

(A) (i) (ii) (iv) (iii)

(B) (ii) (iv) (i) (iii)

(C) (iii) (i) (ii) (iv)

(D) (iv) (i) (ii) (iii)

45. List – I                                                      List – II

(a) Semi– =conductor memory                       (i) Destructive read out

(b) Ferrite core memory                                  (ii) Combinational logic

(c) Magnetic tape memory                              (iii) Non-volatile

(d) Flash memory                                            (iv) EEPROM

Codes :

(a) (b) (c) (d)

(A) (ii) (i) (iii) (iv)

(B) (i) (ii) (iv) (iii)

(C) (ii) (iii) (i) (iv)

(D) (iv) (ii) (i) (iii)

Noise may be defined, in an electrical sense, as an unwanted form of energy tending to interfere with the proper and easy reception and reproduction of wanted signals. Many disturbances of the electrical nature produce noise in receiver, modifying the signal in an unwanted manner. Noise is divided into two groups. Noise whose sources are external to the receiver and other one is noise created within the receiver itself. Various forms of noise created outside the receiver i.e. external noise includes atmospheric and extra-terrestrial noise and industrial noise. Atmospheric noise becomes less severe at frequencies above 30 MHz. Extra-terrestrial noises are solar noise and cosmic noise. They radiate over a very broad frequency spectrum which includes the frequencies, we use for communication. These disturbances are at the eruption of corona flares and sunspots. The noise generated is due to the random motion of electrons, atoms and molecules. Kinetic theory states that the temperature of the system increases due to the motion of the particles.

46. In a communication system, noise is most likely to affect the signal

(A) at a transmitter

(B) in a channel

(C) in the information source

(D) at the destination

47. Indicate the false statement.

(A) HF mixers are generally noiser than HF amplifiers.

(B) Impulse noise voltage is independent of bandwidth.

(C) Thermal noise is independent of the frequency at which it is measured.

(D) Industrial noise is usually of the impulse type.

48. The value of a resistor creating thermal noise is doubled. The noise power generated is therefore

(A) halved

(C) doubled

(D) unchanged

49. One of the following is not a useful quantity for comparing the noise performance of receivers :

(A) Input noise voltage

(B) Equivalent noise resistance

(C) Noise temperature

(D) Noise figure

50. Indicate the noise whose source is in a category different from that of the other three.

(A) Solar noise

(B) Cosmic noise

(C) Atmospheric noise

(D) Galactic noise