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# NTA NET Electronic-Science December-2013 Solved Paper III

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1. In an npn transistor, the expression for avalanche multiplication factor is given by
1. M = 1/ (1 + VCB/B VCBO) n
2. M = (1 + VCB/B VCBO) n
3. M = (1 – VCB/B VCBO) n
4. M = 1/ [1 – (VCB/B VCBO) n]

Where, VCB is collector to base voltage and BVCBO is maximum reverse biasing voltage which may be applied before breakdown between the collector and base terminals.

Answer: d

2. In a bipolar transistor, stability factor for a fixed bias circuit is given by
1. S = 1/ (1 + β)
2. S = 1/ (β – 1)
3. S = (β – 1) 2
4. S = β + 1

Answer: d

3. In a Wein bridge oscillator circuit, the value of frequency can be calculated by the following expression:
1. fo = π RC
2. fo = π LC
3. fo = π L1 (C1 + C2)
4. fo = 1 2π (R21 + R22) (C21 + C22)

Answer: a

4. A square coil has the dimensions 0.2 m × 0.2 m and carrying a current of 3.0 A in a field of 10 wb/m2. The value of Torque is given by
1. 10.2 N – m
2. 1.02 N – m
3. 0.12 N – m
4. 1.2 N – m

Answer: d

5. For a transmission line which isterminated in a normalised impedance Zn, VSWR = 2, the value of normalised impedance is given by
1. 2
2. 3

Answer: a

Answer: a

6. Which of the following circuit comes under the class of sequential logic circuits?
1. Multiplexer
2. ₹ Latch
3. Full Adder
4. ROM

Answer: b

7. The Hammng code for 0110 using even parity is
1. 0010110
2. 1010110
3. 1100110
4. 1110110

Answer: c

8. Phase Lock Loop (PLL) system is used for the detection of
1. PM
2. AM
3. FM
4. QAM

Answer: c

9. A transistor amplifier has a measured S/N of 10 at its input and 5 at its output. The transistor՚s Noise Figure (NF) in dB is
1. 2 dB
2. 3 dB
3. 6 dB
4. 10 dB

Answer: b

10. A signal varies from 20 Hz to 5 KHz is passed using pulse modulation scheme. Minimum sampling rate and number of channels that could be accommodated using TDM (assume each sample takes 10 μs) respectively will be
1. 5 KHz, 5
2. 10 KHz, 5
3. 5 KHz, 10
4. 10 KHz, 10

Answer: d

11. The term (1/jw) on the log-magnitude plot has a slope of
1. – 20 dB/decade
2. + 20 dB/decade
3. – 40 dB/decade
4. + 40 dB/decade

Answer: a

12. The Routh Array is as below: S6 1 8 20 6 S5 2 12 16 S4 2 12 16 S3 0 0 The row of zero of this ray will be replaced by coefficients of:
1. S4 + 12 S2 + 16
2. S3 + 3 S
3. S4 + 6 S2 + 8
4. S3 + 12 S

Answer: b

13. Zener breakdown mechanism occurs in reverse biased PN junction
1. When P and N regions are lightly doped.
2. When P and N regions are heavily doped.
3. Are of silicon material only.
4. When P and N regions are equally doped.

Answer: b

14. The operation of a Photo-diode involves
1. Photo-conductive effect
2. Photo-voltaic effect
3. Photo-emissive effect
4. Photo-multiplicative effect

Answer: c

15. A UJT has RBB = 10 K and RB2 = 4 K. Its intrinsic stand-off ratio is
1. 0.6
2. 0.4
3. 2.4
4. 3.5

Answer: a

16. The triggered voltage of a SCR is close to
1. 0.3 V
2. 0.7 V
3. 3 V
4. Breakdown voltage

Answer: b

17. A thyristor can be used as
1. An amplifier
2. A resistor
3. A switch
4. A power source

Answer: c

18. Which of the following is an advantage to use fiber optic data transmission?
1. Resistance to the data theft
2. Fast data transmission rate
3. Low noise level
4. All of the above

Answer: d

19. A breakdown which is caused by cumulative multiplication of carriers through field induced impact ionization occurs in
1. Avalanche diode
2. Tunnel diode
3. Varactor diode
4. Gunn diode

Answer: a

20. Transfer function of a system is necessary for the calculation of
1. The time constant
2. The output for a given input
3. The steady state gain
4. The order of the system

Answer: b

21. If one or more pairs of simple roots are located on imaginary axis of the s-plane but there are no roots in the right half of s-plane, the response due to initial condition will
1. Decrease to zero as time approaches infinity.
2. Increase as time approaches infinity.
3. Be undamped sinusoidal oscillations.
4. Be damped unsinusoidal oscillation and the damping factor will depend upon the relative location of the roots on the imaginary axis.

Answer: c

22. 8255A Programmable Peripheral Interface IC has got the 24 I/O lines in the following way (General form) :
1. Port A with 8 input lines, Port B with 8 output lines, Port C (upper nibble) with 4 input lines and Port C (lower nibble) with 4 output lines.
2. Port A with 8 input/out lines, Port B with 8 input lines and Port C with 8 output lines.
3. Port A with 8 input lines, Port B with 8 output lines and Port C with 8 bits as either input or output lines.
4. Port A with 8 lines as input/output lines, Port B with 8 lines as input/output lines, Port C (lower nibble) with 4 lines as input/output lines. Port C (upper nibble) with 4 lines as input/output lines.

Answer: d

23. C program is as follows: The result of the program is int i; / ⚹ … declare integer i … ⚹ /i = 10; / ⚹ … set i to 10 … ⚹ /i = i + ‘A’ / ⚹ … add character A … ⚹ // ⚹ … to integer i … ⚹ /print f ( “i =% d” i)
1. 55
2. 51
3. 71
4. 75

Answer: d

24. Consider the following conditional expression z = (x > y) ? x: y; if x = 2 and y = 8, the value of z is
1. 2
2. 8
3. 6
4. 10

Answer: b

25. int Net = 0; if x < 50 if (y > 5) Net = x + y; else Net = x – y; For this C program segment, x = 55 and y = 5, then the value Net is
1. 0
2. 60
3. 50
4. 55

Answer: a

26. In 8253 programmable interval timer, in which modes, the counting is neither enabled nor disabled?
1. 0 and 4
2. 1 and 5
3. 1 and 4
4. 3 and 5

Answer: b

27. In which mode of 8259A programmable interrupt controller, all the Interrupt Requests (IRs) are arranged from highest to lowest with IR0 as the highest and IR1 as the lowest?
1. Fully Nested Mode
2. Automatic Rotation Mode
3. Specific Rotation Mode
4. Simple Rotation Mode

Answer: a

28. In an OPAMP, following characteristics are given:
1. PSRR (Power Supply Rejection Ratio) is 0
2. Thermal Drift is defined in terms of μ Amperes/° C.
3. Thermal drift is defined in terms of μV/° C.
4. Slew rate is defined in terms of V/μs.

Which one of the following is correct?

1. 1 and 2 only
2. 1 and 3 only
3. 1,3 and 4
4. 1,2 and 4

Answer: c

29. Consider the following statement:
1. A flip-flop is used to store 1-bit of information.
2. Race-around condition occurs in J-K flip-flop when both the inputs are 1.
3. Master-slave configuration is used in flip-flop to store 2-bits of information.
4. A transparent latch consists of D type flip-flop.

Which of the following statements is/are true?

1. 1 only
2. 1,3 and 4
3. 1,2 and 4
4. 2 and 3 only

Answer: c

30. An AM demodulator can be implemented with
1. A linear multiplier followed by a low pass filter.
2. A linear multipler followed by a high-pass filter.
3. A diode followed by low pass filter.
4. A linear multiplier followed byband-stop filter.

The correct answer is:

1. 1 only
2. 3 only
3. 1 and 3
4. 4 only

Answer: c

31. In feedback control system, relative stability can be calculated using
1. Routh-Hurwitz Array
2. Nyquist plot
3. Polar plot
4. Root Locus Techniques

Correct answer is

1. All of the above
2. 1 and 2 only
3. 2 and 4 only
4. 2,3 and 4

Answer: c

32. In comparison to LED, LASER has
1. High emission frequency.
2. No tuning arrangement.
3. Wide spectral bandwidth.
4. Provision for confinement.

Of these statements:

1. 1,2 & 4 are correct.
2. 1,2, & 3 are correct.
3. 1 & 4 are correct.
4. 2 & 3 are correct.

Answer: c

33. The turn-off time of an SCR can be reduced by
1. Quick withdrawal of the gate voltage.
2. Reducing life-time by doping with gold.
3. Applying a negative voltage pulse to the gate.

Of these statements:

1. 1,2 and 3 are correct.
2. 1 and 2 are correct.
3. 1 and 3 are correct.
4. 2 and 3 are correct.

Answer: d

34. Consider the following statements regarding a semiconductor:
1. Acceptor level lies close to the valence band.
2. Donor level lies close to the valence band.
3. n-type semiconductor behavesas a conductor at zero Kelvin.
4. p-type semiconductor behaves as an insulator at zero Kelvin.

Of these statements:

1. 2 and 3 are correct.
2. 1 and 3 are correct.
3. 1 and 4 are correct.
4. 3 and 4 are correct

Answer: c

35. Transfer function for a control system is defined for where
1. Linear system
2. Nonlinear system
3. Time invariant system
4. Time variant system
1. 1 and 3
2. 2 and 4
3. 1 and 4
4. 2 and 3

Answer: a

36. Tri state Buffers provide
1. Reduction of current consumption in the circuit.
2. Isolation from input to output.
3. High impedance during OFF state.
4. Low impedance during ON state.
1. 1 and 4
2. 2 and 4
3. 1 and 2
4. 1 and 3

Answer: d

37. Consider the following:
1. CE stage
2. CC stage
3. OP amp
4. CB stage

The correct sequence of the input impedance in increasing order is:

1. 4,1, 2,3
2. 1,4, 2,3
3. 1,2, 4,3
4. 4,2, 1,3

Answer: a

38. The various components in super heterodyne receiver is arranged as
1. AM Detector
2. Mixer
3. RF Amplifier
4. AF Amplifier

The correct sequence is

1. 3,2, 1,4
2. 1,2, 4,3
3. 3,2, 4,1
4. 2,1, 3,4

Answer: a

39. Fora unity feedback control system having an open-loop transfer function G (S) = [K (S + 2) ] /S2 (S4 + 7 S + 12) The error constant Kp, Kv and Ka respectively are
1. ∞ ∞ K/6
2. 0,0, K/6
3. ∞ 0, K/6
4. 0, ∞ K/6

Answer: a

40. Arrange in ascending order the following logic families based on power delay products
1. ECL
2. TTL
3. CMOS

Codes:

1. 2,3, 1
2. 2,1, 3
3. 1,2, 3
4. 3,2, 1

Answer: a

41. Consider the following four common type of transistors:
1. Point Contact Transistor
2. Bipolar Junction Transistor
3. MOS Field Effect Transistor
4. Junction Field Effect Transistor

Correct arrangement of these transistors in the increasing order of input impedance is

1. 1,2, 4,3
2. 1,2, 3,4
3. 2,1, 3,4
4. 2,1, 4,3

Answer: d

42. If the various logic families are arranged in the ascending order of their fan-out capabilities, the sequence will be
1. TTL, DTL, ECL, MOS
2. DTL, TTL, MOS, ECL
3. MOS, DTL, TTL, ECL
4. ECL, TTL, DTL, MOS

Answer: c

43. Consider the following waves/rays:
1. UV Rays
2. X Rays
3. Visible light
4. UHF waves

The correct sequence of the descending order in terms of frequency is:

1. 3,1, 2,4
2. 4,3, 1,2
3. 2,1, 3,4
4. 2,4, 1,3

Answer: c

44. The structure of a decision table, divided into four parts like 1 4 2 3
1. Condition Stub
2. Condition Entries
3. Action Stub
4. Action Entries
1. 1,2, 4 and 3
2. 2,4, 3 and 1
3. 1,3, 4 and 2
4. 1,4, 2 and 3

Answer: c

45. The parameters associated with time response of control system are
1. Delay time (td)
2. Settling time (ts)
3. Rise time (tr)
4. Peak time (tp)

Arrange the above in the order, the parameter which is having minimum time to the parameter which has got the maximum time.

1. 1,4, 2 and 3
2. 1,3, 2 and 4
3. 1,4, 3 and 2
4. 1,3, 4 and 2

Answer: d

46. In the Assembly program, the following steps are to be followed. Find the sequence in which the program to be written for 8085 microprocessor.
1. Initialization of variables.
2. Initialization of stack.
3. Enable or disable interrupts.
4. Program should be completedwith last line as ‘END’ statement.
1. 1,3, 2 and 4
2. 1,2, 3 and 4
3. 2,1, 3 and 4
4. 2,3, 1 and 4

Answer: c

47. Match the following lists:
 List-I List-II Alpha of TransistorBeta of TransistorCMRR (Common Mode Rejection Ratio)PSRR (Power Supply Rejection Ratio) Greater than 1∞Less than 1Equal to 0
• A
• B
• C
• D
• 3
• 1
• 2
• 4
• 4
• 1
• 2
• 3
• 1
• 2
• 3
• 4
• 2
• 1
• 3
• 4

Answer: a

48. Match the following lists:
 List-I List-II MagnetronPin diodeKlystronGunn diode DetectorBunchingLow Power Oscillatorπ-mode
• A
• B
• C
• D
• 2
• 3
• 4
• 1
• 1
• 2
• 3
• 4
• 3
• 1
• 2
• 4
• 4
• 1
• 2
• 3

Answer: d

49. Match the following lists:
 List-I List-II CompandingSquelchPreemphasisDouble conversion Improving image rejectionVariation of step rise in quantisationMuting the receiverBoosting of higher modulating frequencies at the transmitter
• A
• B
• C
• D
• 2
• 3
• 4
• 1
• 2
• 1
• 4
• 3
• 1
• 2
• 3
• 4
• 1
• 2
• 4
• 3

Answer: a

50. Match the following lists:
 List-I List-II 74150741527415374157 Quad 2: 1 MultiplexerDual 4: 1 Multiplexer8: 1 Multiplexer16: 1 Multiplexer
• A
• B
• C
• D
• 1
• 2
• 3
• 4
• 4
• 3
• 2
• 1
• 4
• 2
• 3
• 1
• 2
• 1
• 4
• 3

Answer: b

51. Match the following lists:
 List-I (Characteristic of the device) List-II (Device) Voltage controlled deviceCurrent controlled deviceConductivity modulated deviceNegative conductance device BJTUJTFETIMPATT
• A
• B
• C
• D
• 2
• 3
• 1
• 4
• 2
• 3
• 4
• 1
• 3
• 1
• 4
• 2
• 3
• 1
• 2
• 4

Answer: c

52. Match the following lists:
 List-I List-II Optical fiber communicationMobile communicationDigital communicationAnalog communication FDMTDMCDMAWavelength-Division Multiplexing (WDM)
• A
• B
• C
• D
• 1
• 3
• 2
• 4
• 4
• 3
• 2
• 1
• 2
• 4
• 1
• 3
• 3
• 1
• 2
• 3

Answer: b

53. In the following question Match List-I with List-II
 List-I List-II Bode՚s-Plot representationNyquist DagramNichols ChartsRoot-locus Method not a frequencydomaintechnique.low frequency and high frequency characteristics of the transfer function can be determineddecides the Stability criteriaalso known as Polar plots
• A
• B
• C
• D
• 4
• 3
• 1
• 2
• 4
• 3
• 2
• 1
• 3
• 4
• 1
• 2
• 2
• 3
• 4
• 1

Answer: d

54. The following are features of a micro controller 8051:
1. 4 k bytes of ROM or EPROM
2. 128 k bytes of data memory
3. Four programmable I/O ports
4. Three 16 bit timer/event counters.
1. 1,2 and 3
2. 1,2 and 4
3. 1,3 and 4
4. 2,3 and 4

Answer: a

55. Identify the peripheral devices for their applications.
 List-I List-II 8155827982538251 Serial CommunicationTimers and CountersKeyboard and display interfaceAdditional input/output lines to processor
• A
• B
• C
• D
• 2
• 3
• 4
• 1
• 3
• 4
• 1
• 2
• 4
• 1
• 2
• 3
• 4
• 3
• 2
• 1

Answer: d

56. Match the following lists:
 List-I List-II Stability of Control SystemUnstability of Control SystemFrequency responseDamped Oscillation Oscillation in which the amplitude decreases with timeAll roots of characteristic equation have negative real partSteady state responseAny root of characteristic equation has a positive real part
• A
• B
• C
• D
• 4
• 2
• 3
• 1
• 2
• 4
• 3
• 1
• 2
• 4
• 1
• 3
• 4
• 2
• 1
• 3

Answer: b

• Assertion (A) : In amplifiers, it is easy to compare two powers on a Logarithmic rather than on linear scale. It is called decibel.
• Reason (R) : Decibel is defined as N = 10 log P2/P1, where P2 is output power and P1 is input power.
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 and R is false.
4. A is false and R is true.
Answer: a
• Assertion (A) : Magnetron is not cross field devices.
• Reason (R) : They make use of electric and magnetic fields simultaneously. The fields are perpendicular to each other.
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 and R is false.
4. A is false and R is true.
Answer: d
• Assertion (A) : TDM can be employed to transmit channels having unequal bandwidths.
• Reason (R) : If sampling theorem is strictly followed, any analog signal can be reconstructed back from the samples.
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 and R is false.
4. A is false and R is true.
Answer: b
• Assertion (A) : A NAND gate is called a Universal logic element.
• Reason (R) : Any logic function can be realized using NAND gates alone.
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 and R is false.
4. A is false and R is true.
Answer: a
• Assertion (A) : The stability of a control system can be determined from the location of roots of characteristic equation.
• Reason (R) : For stability the roots should lie on the left half of s-plane.
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 and R is false.
4. A is false and R is true.
Answer: a
• Assertion (A) : The intrinsic Fermi level of a semiconductor does not lie exactly at the middle of the energy band gap.
• Reason (R) : The densities of the available states in valence and conduction bands of an intrinsic semiconductor areequal.
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 and R is false.
4. A is false and R is true.
Answer: d
• Assertion (A) : The operating principle of Laser is based on stimulated emission process.
• Reason (R) : In coherent radiation, the emitted photons have same phase, same polarization and same direction with the incident photon.
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 and R is false.
4. A is false and R is true.
Answer: a
• Assertion (A) : A microprocessor interfaced with inputs, outputs and other peripheral devices is also called a micro controller system and is capable of controlling the process.
• Reason (R) : The microprocessor is a device which processes the instructions.
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 and R is false.
4. A is false and R is true.
Answer: a
• Assertion (A) : In control system design, the transfer function consists of both poles and zeros. To make the system stable, the poles plotted in Bode plot should be near to origin.
• Reason (R) : The zeros must be also near to origin.
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 and R is false.
4. A is false and R is true.
Answer: d
• Assertion (A) : A p-channel enhancement MOSFET based transistor can be turn on prematurely.
• Reason (R) : Most contaminants in MOS fabrication are mobile positively charged ions and they get trapped between the gate and the substrate in an n-channel enhancement MOSFET, whereas they are trapped on the other side of the substrate in the case of a p-channel enhancement MOSFET.
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 and R is false.
4. A is false and R is true.
Answer: a

## Read the Paragraph and Answer the Question Nos. 71 to 75

The field effect transistor is a semiconductor device which depends for its operation on the control of current by an electric field. There are two types of field effect transistor, the Junction Field Effect Transistor (JFET) and Metal-Oxide-Semiconductor (MOSFET) FETs operation depends upon the flow of majority carriers only. It is therefore a unipolar device. BJT is a bipolar device. FET is relatively immune to radiation and it exhibits a high input resistance tipically many mega-ohms. It is less noisy than a tube or a bipolar transistor. It exhibits no offset voltage at zero drain current, and hence makes an excellent signal chopper. FETs are more temperature stable than BJTs. JFET is three terminal devices with gate applied potential control the flow of charges from source to drain. The n-channel MOSFET consists of a lightly p-type substrate into which two highly doped n + regions are diffused. These n + sections, which will act as the source and drain. A thin layer of insulating SiO2 is grown over the surface of the structure and holes are cut into the oxide layer, allowing contact with the source and drain. This layer results in an extremely high input resistance.

1. The point above the drain voltage, where there is no increase in drain current in a JFET is called as
1. Break down point
2. Pinch off point
3. Knee point
4. Critical point

Answer: b

2. FET is disadvantageous in comparison with BJT because of
1. High input impedance
2. Low noise
3. High gain bandwidth behaviour
4. Current controlled behaviour

Answer: d

3. For an n-channel silicon FET with α = 3 × 10 – 4 cms and ND = 1015 electron/cm3, find the pinch is of voltage. [∈ = 12 ∈ 0 π ∈ 0 = 9 × 109 (Newton – m2) /Coulomb]
1. 6.00 V
2. 5.4 V
3. 6.8 V
4. 4.5 V

Answer: c

4. An FET is a better chopper than BJT because it has
1. Higher series on resistance
2. Lower input current
3. Higher input impedance
4. Lower off-set voltage

Answer: d

5. For an n-channel enhancement mode MOSFET the drain current
1. Decreases with increase in drain current.
2. Decreases with decreases in drain voltage.
3. Increases with increase in drain voltage.
4. Increases with decrease in gate voltage.

Answer: c