[Solved] UGC NET Electronic Science August 2024 Question Paper with Answer Key & Detailed Solutions

UGC NET Electronic Science August 2024 Question Paper with Answer Key and Detailed Solutions
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1.

The peak concentration in the lateral autodoping profile is a function of the following parameters:

(a) Temperature
(b) Surface concentration in the buried layer
(c) Applied voltage
(d) Growth time

Options:

A. (a) and (b) only
B. (a) and (c) only
C. (a), (b) and (c) only
D. (a), (b) and (d) only

Answer: D

2.

A parallel plate capacitive transducer having air as dielectric between the plates, plate area is 50 mm × 50 mm and plate spacing is 0.5 mm. The displacement causes the capacitance to change by 10 pF. The sensitivity of the capacitive displacement transducer is:

A. 50.23 pF/mm
B. 66.67 pF/mm
C. 61.25 pF/mm
D. 59.12 pF/mm

Answer: B

3.

In a charge coupled device, the charge storage and transfer action is controlled by one of the following:

A. Drain Electrode
B. Gate Electrodes
C. Source Electrodes
D. Back of the Substrate

Answer: B

4.

Following set of instructions in 8086 searches a table of 100 bytes for 0AH. Select the correct option:

MOV CX, 100
MOV AL, 0AH

(a) SCASB
(b) CLC
(c) CLD
(d) REPNE SCASB
(e) JCXZ NOT_FOUND

NOT FOUND : END

A. (a), (d), (b), (e), (c)
B. (b), (d), (a), (e), (c)
C. (c), (d), (a), (e), (b)
D. (b), (d), (c), (e), (a)

Answer: C

5.

The band gap of a semiconductor material that can be considered for making solar cell will be:

A. < 1 eV
B. Between 2 & 3 eV
C. Between 1 & 2 eV
D. > 3 eV

Answer: C

6.

Arrange the following in the decreasing order of their Bandgap (eV) at 300K.

(a) GaAs
(b) Si
(c) Ge
(d) ZnO
(e) InSb

Order: ZnO > GaAs > Si > Ge > InSb

Answer: D

7.

A thyristor having the equivalent capacitance of the depletion layer of reverse biased junction as 20 picofarad can be fired with a dv/dt of 120 V/µsec. The capacitive current flowing through the junction will be:

i = C (dv/dt)

A. 1.8 mA
B. 2.4 mA
C. 3.6 mA
D. 5.9 mA

Answer: B

8.

The circular loop of radius a carries current I. The magnetic field at an observation point in spherical coordinates is asked.

A. Hr = (I πa² cosθ) / (2π r³)
B. Hr = (I πa² cosθ) / (2π r²)
C. Hr = (I πa² sinθ) / (2π r³)
D. Hr = (I πa² sinθ) / (4π r³)

Answer: A

9.

A PMMC instrument has a three-resistor Ayrton shunt connected in parallel with it to make an ammeter. The current range when connected to terminal C is asked.

A. 10 mA
B. 1 mA
C. 100 mA
D. 1 A

Answer: C

10.

Match the List-I with List-II (Input waveform with Output waveform).

Answer: A

11. Match List-I with List-II (Programmable Logic Devices)

(a) PROM
(b) PLA
(c) PAL
(d) EEPROM

Answer: B

(a) → III (AND array fixed, OR programmable)
(b) → I (Both AND and OR programmable)
(c) → IV (AND programmable, OR fixed)
(d) → II (Reprogrammable memory)

12. For microwave sources and devices, identify the correct statements.

Answer: D

Correct statements: (a) and (e).

13. Arrange the following in increasing order of electron mobility at 300 K.

(a) Si
(b) Ge
(c) GaP
(d) InAs

Answer: D

Increasing order:
GaP < Si < Ge < InAs

14. Arrange the Z-parameters in descending order.

(a) Z11
(b) Z21
(c) Z12
(d) Z22

Answer: B

Descending order:
Z22 > Z11 > Z21 > Z12

15. Match Maxwell’s equations with their integral forms.

Answer: C

(a) → IV
(b) → I
(c) → II
(d) → III

16. Reflection of plane electromagnetic wave at normal incidence.

Answer: D

Er/Ei = ( √ε₁ − √ε₂ ) / ( √ε₁ + √ε₂ )

17. Determine the operating point of the transistor circuit.

Answer: D

Collector current Ic = 1.86 mA
Collector voltage Vc = 6.28 V

18. Why does Si/SiGe HBT have lower cutoff frequency than GaAs and InP HBTs?

Answer: A

Because silicon has lower carrier mobility.

19. Match the control system block diagrams with their equivalent forms.

Answer: B

20. Identify the blocks in the CRO block diagram.

Answer: C

I → Vertical Amplifier
II → Delay Line
III → Trigger Circuit
IV → Time Base Generator
V → Horizontal Amplifier

21. A 6-bit DAC has step size of 50 mV. Find full-scale output and resolution.

Answer: D

Full scale voltage = 3.15 V
Resolution = 1.587%

22. For the control system output:
c(t) = 1 + 0.25e⁻⁵⁰ᵗ − 1.25e⁻¹⁰ᵗ

Answer: D

Natural frequency = 22.36 rad/s
Damping ratio = 1.34

23. Find the voltage gain of the common source FET circuit.

Answer: B

Voltage gain ≈ −7.9

24. Arrange logic families in increasing order of noise margin.

Answer: A

ECL < IIL < TTL < MOS

25. Arrange sections of a firing pulse generator using inverse cosine control.

Answer: B

Phase shift circuit → Isolating transformer → Level comparator → Clock pulse generator → Flip-flop

26. Match the List-I with List-II (8051 Timer Modes)

List-I (Timer Mode)

(a) Mode 0
(b) Mode 1
(c) Mode 2
(d) Mode 3

List-II (Operation)

I. 16-bit timer/counter
II. Two 8-bit timers
III. 13-bit timer/counter
IV. Auto-reload of TL from TH

Answer: (a) → III, (b) → I, (c) → IV, (d) → II

27. Shannon Capacity

For a telephone circuit with SNR = 1000 and bandwidth = 2.7 kHz, find the channel capacity.

A. 26.9 Kbps
B. 2.7 Kbps
C. 3.32 Kbps
D. 29.6 Kbps

Answer: A (≈ 26.9 Kbps)

28. Satellite Bands

List-I

(a) C-Band
(b) X-Band
(c) Ku-Band
(d) Ka-Band

List-II (GHz)

I. 7.9–8.4
II. 27–30
III. 5.9–6.4
IV. 14–14.5

Answer: (a) → III, (b) → I, (c) → IV, (d) → II

29. EEG & ECG Matching

List-I

(a) Gamma (γ)
(b) Theta (θ)
(c) QRS interval
(d) PR interval

List-II

I. 0.1–0.2 s
II. 0.05–0.10 s
III. 4–8 Hz
IV. 22–30 Hz

Answer: (a) → IV, (b) → III, (c) → II, (d) → I

30. Superheterodyne Receiver Sequence

(a) Mixer
(b) RF stage
(c) Antenna
(d) Detector
(e) IF Amplifier

Correct Sequence:

Answer: B

31. Thyristor Matching

List-I

(a) BCT
(b) RCT
(c) ETO
(d) TRIAC

List-II

I. Bidirectional triggering (Quadrants I & III)
II. Turn-on & turn-off control
III. Bipolar-controlled thyristor
IV. Built-in antiparallel diode

Answer: (a) → III, (b) → IV, (c) → II, (d) → I

32. Segregation Coefficient Order

(a) Al
(b) As
(c) B
(d) C
(e) P

Answer: (a), (d), (b), (e), (c)

33. Counter Valid States (4-bit)

(a) Ring counter
(b) Johnson counter
(c) Decade counter
(d) Ripple counter

Answer: (a) → (b) → (c) → (d)

34. Series RLC Impedance Order

(a) ω = 4800 Hz
(b) ω = 4000 Hz
(c) ω = 3200 Hz
(d) ω = 4400 Hz

Answer (Descending |Z|):

35. Open Loop vs Closed Loop Systems

(a) More stable
(b) More reliable
(c) Easier to build
(d) Cannot be optimized (false)

Answer: C — (a) and (c) only

36. For asynchronous sequential circuits:

Memory elements are either unclocked FFs or time delay elements
Change in input signal can affect memory elements upon activation of clock signal also
Can operate faster than synchronous circuit because of absence of clock signal
Easier to design

(a) and (c) only
(a), (c) and (d) only
(a), (b) and (c) only
(c) and (d) only

Answer: Option A

Solution: In async sequential circuits, the memory is typically in the form of unclocked latches or inherent delays...and they do not wait for clock edge, they can change state immediately upon input changes

37. For the Instruction (in case of 8051)
DIV A,B
Which of the following statements is not correct?

A. The overflow flag is cleared to 0 unless B holds 00H before the DIV.
B. The overflow flag is set to 1 to show division by 0.
C. The carry flag is always set.
D. This instruction put the integer part of quotient in register A and the integer part of the remainder in register B.

Answer: Option C

Solution: For the instruction the carry flag is always cleared, not set.

Previous yr Question papers with Full Explanations →

38. The effective density of states in the conduction band N_c (cm^-3) for Si & GaAs at 300K are:

Si = 2.86 × 10¹⁹
Si = 2.66 × 10¹⁹
GaAs = 4.7 × 10¹⁷
GaAs = 7.0 × 10¹⁸

A. (a) and (c)

B. (a) and (d)

C. (b) and (c)

D. (b) and (d)

Answer: Option A

39. For the 8051 microcontroller, during its operations in the serial data mode 2 (Multi-Processor Mode) which of the following statements are correct:

11 bits are transmitted
The baudrate = (2^SMOD / 64) × oscillator frequency
The baudrate = (2^SMOD / 32) × (timer 1 overflow frequency)
The start bit is not discarded
The stop bit is discarded

A. (a) and (c) only

B. (a) and (d) only

C. (b) and (e) only

D. (a), (b) and (e) only

Answer: Option D 40. (B)

41. An operational amplifier as shown below has a poor open loop voltage gain of 45 but otherwise it is ideal. Find the closed loop gain of the amplifier.

[Non-inverting op-amp configuration. Feedback resistor R_f = 20kΩ, ground-side resistor R₁ = 5kΩ. Input voltage V_in at the non-inverting terminal.]

A. 5

B. -4

C. 4.5

D. 4

Answer: Option C

Solution: Non-inverting op-amp = 1+ 20/5 = 5

Open loop gain 45 (given)

closed loop gain = 5/(20+5) = 1/5

Closed-loop gain of the OPamp is 45/(1+(1/5).45) = 4.5

42. A piezoelectric transducer having a wafer of piezoelectric crystal material with a relative permittivity of 700 is sandwiched between two plated electrodes. The plate dimensions is 5 mm × 5 mm. The piezoelectric crystal material has a thickness 2 mm. When a force of 10 N is applied, the piezoelectric transducer produces an output voltage of 40 V. The respective value of its voltage sensitivity and charge sensitivity is?

A. 0.04 Vm/N, 247.52 pC/N
B. 0.05 Vm/N, 309.4 pC/N
C. 0.04 Vm/N, 261.12 pC/N
D. 0.05 Vm/N, 319.8 pC/N

Answer: Option B

Solution:

C = ε.ε0 * A/d = 77.5 pF

Q/F = CV/10 = 310 pC/N

Voltage Sensitivity = V/F = V*thickness/10 = 40*2*10^(-3)/10 = 0.008

43. (A)

44. What will be the content of register AX when the following set of instructions are executed in 8086 microprocessor?

MOV AX, 31H
ADD AL, 39H
AAA

A. 0070H

B. 006AH

C. 0100H

D. 116AH

Answer: Option C

45. For the given circuit, the maximum power delivered to the load shall be:

A voltage source V_th in series with resistance R_th, connected to a load resistor R_L.

A. V_th² / R_th

B. V_th² / 2R_th

C. V_th² / 4R_th

D. V_th² / 8R_th

Answer: Option C

46. For 8086 microprocessor interrupt system, which of the following statements are true?

(a) Type 0 - Divide Error
(b) Type 1 - 1 byte break
(c) Type 2 - single step
(d) Type 4 - overflow (INTO)

A. (a) and (c) only

B. (b) and (d) only

C. (b) and (c) only

D. (a) and (d) only

Answer: option D

47. The min terms for the following 'f_min' will be:

f_min = A'C' + A'D + A'B + BD

A. f = Σ_m(0, 1, 5, 6, 9, 13, 15)
B. f = Σ_m(2, 8, 9, 10, 12, 14)
C. f = Σ_m(0, 1, 3, 4, 5, 6, 7, 13, 15)
D. f = Σ_m(1, 5, 7, 9, 10, 12, 14, 15)

Answer: Option C

Solution

Finding Minterms for the Boolean Expression

Given Boolean expression:

F_min = A'C' + A'D + A'B + BD

We determine all combinations of A, B, C, and D for which the function is equal to 1.

1. A'C'

Here A = 0 and C = 0, while B and D can be anything.

0000 = m₀
0001 = m₁
0100 = m₄
0101 = m₅

2. A'D

Here A = 0 and D = 1, while B and C vary.

0001 = m₁
0011 = m₃
0101 = m₅
0111 = m₇

3. A'B

Here A = 0 and B = 1, while C and D vary.

0100 = m₄
0101 = m₅
0110 = m₆
0111 = m₇

4. BD

Here B = 1 and D = 1, while A and C vary.

0101 = m₅
0111 = m₇
1101 = m₁₃
1111 = m₁₅

Final Minterm Form:

F(A,B,C,D) = Σm(0,1,3,4,5,6,7,13,15)

48. Match the List-I with List-II.

List-I (Multiplexing Type)	List-II (No. of Channels)
(a) T1 carrier system	I. 96, 64 kbps channels
(b) T2 carrier system	II. 672, 64 kbps channels
(c) T3 carrier system	III. 24, 64 kbps channels
(d) T4 carrier system	IV. 4032, 64 kbps channels

Choose the correct answer from the options given below:

	(a)	(b)	(c)	(d)
A.	III	I	II	IV
B.	III	I	II	IV
C.	II	III	I	IV
D.	I	IV	II	III

Answer: Option B

49. For an QPSK modulator with an input data rate (f_d) of 10 Mbps and a carrier frequency of 70 MHz, the minimum double-sided Nyquist Bandwidth and Baud rate will be:

A. 2.5 MHz and 5 Megabaud
B. 5 MHz and 5 Megabaud
C. 5 MHz and 2.5 Megabaud
D. 5 KHz and 2.5 Megabaud

Answer: Option B

Solution:

Solution: baud rate = bit rate / bits per symbol = 10 Mbps / 2 = 5 Megabaud Bandwidth = bit rate / bits per symbol = 10 / 2 = 5 MHz

50. With regard to the quantum efficiency of a Photodiode, which of the following is not correct?

A. The depletion region must be kept thin to reduce the transit time.
B. The depletion region must be sufficiently thick to allow a large fraction of incident light.
C. Germanium Photodiodes & Group III-V Photodiodes have high quantum efficiency.
D. Silicon Photodiodes can reach 100% quantum efficiency near the 0.8-0.9 μm region with an antireflection coating.

Answer: Option A

51. For a single mode optical fiber cable with attenuation of 0.25 dB/km, the optical power (in dBm), 100 km away, from a 0.1 mW light source will be:

A. -10 dBm
B. -25 dBm
C. -30 dBm
D. -35 dBm

Answer: Option D

Solution: 0.1mW = 10log10(0.1) = -10 dBm

Optical power loss = 0.25 * 100 = 25 dB

Optical power at receiver = -10-25 = -35 dBm

52. The high frequency and high speed issues of the MOSFET are controlled by the following through the channel:

(a) Capacitance charging times
(b) Capacitance discharging times
(c) Transit time of the carriers
(d) Series resistances associated with the source & the drain

A. (a) and (b) only
B. (a) and (c) only
C. (a), (c) and (d) only
D. (b) and (d) only

Answer: Option B

53. Following is true for a closed loop op-amp based non-inverting amplifier:

(a) It is a voltage shunt feedback amplifier
(b) It has its bandwidth under feedback given by

B_f = (UGB) · K ; K = Attenuation factor
A_f
by A_f = Closed loop gain
(c) It has its input resistance under feedback given by R_if = R_i (1 + AB); R_i = input resistance, A = Open loop gain, B = Feedback gain
(d) It is a voltage series feedback amplifier

A. (a) and (c) only
B. (a) and (b) only
C. (b) and (d) only
D. (c) and (d) only

Answer: Option D

54. A silicon sample is doped with 10¹⁵ Arsenic atoms/cm³. What is the equilibrium hole concentration P_n at 300°K if the intrinsic hole & electron concentration is n_i = 1.5 × 10¹⁰ atoms/cm³.

A. 1.5 × 10¹⁰ cm^-3
B. 2.25 × 10⁵ cm^-3
C. 3.25 × 10¹⁰ cm^-3
D. 4.25 × 10¹⁰ cm^-3

Answer: Option B

Solution

n0*p0 = ni^2

55. (B)

56. Match the List-I with List-II. For a coaxial cable in which the dielectric has inner radius 'a' and outer radius 'b' where σ is conductivity.

List-I

(Transmission line parameter)

(a) Capacitance per unit length
(b) Conductance per unit length
(c) Inductance per unit length
(d) Characteristic Impedance

List-II

(Expression)

$ \frac{2\pi\epsilon}{\ln\left(\frac{b}{a}\right)} $
$ \frac{1}{2\pi}\sqrt{\frac{\mu}{\epsilon}}\ln\left(\frac{b}{a}\right) $
$ \frac{2\pi\sigma}{\ln\left(\frac{b}{a}\right)} $
$ \frac{\mu}{2\pi}\ln\left(\frac{b}{a}\right) $

Choose the correct answer from the options given below:

	(a)	(b)	(c)	(d)
A.	II	I	III	IV
B.	III	I	IV	II
C.	IV	I	II	III
D.	I	III	IV	II

Answer: Option B

57. Arrange the following materials with regard to their thermal conductivities when used in packaging in the units kW/cm-°C in the decreasing order.

(a) Silicon
(b) Au
(c) Epoxy (fused Silica filler)
(d) Alumina (Al₂O₃)
(e) Common Cu Alloys

A. (a), (c), (b), (d), (e)
B. (a), (c), (d), (b), (e)
C. (b), (e), (a), (c), (d)
D. (b), (e), (a), (d), (c)

Answer: D

58. (B)

59. For an angle modulated signal

$$ X(t) = 3 \cos \left[ 2\pi \cdot 10^{6} t + 2 \sin \left( 2\pi \cdot 10^{4} t \right) \right] $$

its maximum phase deviation and maximum frequency deviation respectively are:

A. 3 rad & 10⁴ Hz
B. 2 rad & 10⁴ Hz
C. 2 rad & 2 × 10⁴ Hz
D. 3 rad & 2 × 10⁴ Hz

Answer: Option C

Solution

Phase deviation = kp.Am = 2sin(2*pi*10^4t)

Maximum phase deviation = 2rad

For frequency modulation frequency of the modulated signal changes in accordance to amplitude of the message signal

d(2sin(2*pi*10^4t)) / dt

2*2*pi*cos(2*pi*10^4t)

So, maximum frequency deviation = 2*10^4 Hz

60. Match the List-I with List-II.

List-I (Thermocouple)

(a) K Type chromel-alumel thermocouple
(b) T Type Copper-constantan thermocouple
(c) S Type Platinum-Platinum (90%) rhodium (10%) thermocouple
(d) J Type Iron-constantan thermocouple

List-II (Temperature range)

0 to 1500°C
-200 to +1200°C
-150 to +350°C
-150 to +1000°C

Choose the correct answer from the options given below:

	(a)	(b)	(c)	(d)
A.	IV	I	II	III
B.	I	IV	III	II
C.	III	IV	I	II
D.	II	III	I	IV

Answer: Option D

61. (D) 62. (C)

63. Hardware descriptive language (HDL)

(a) Describe logic diagrams and complex digital circuits
(b) Describes behaviour of analog circuits using simulation techniques
(c) Two HDL supported by IEEE are VHDL and Verilog HDL
(d) Both Verilog and VHDL are based on 'C' Programming

A. (a) and (d) only

B. (a) and (c) only

C. (a), (c) and (d) only

D. (b), (c) and (d) only

Answer: Option B

Solution

HDL for not analog circuits

VHDL is not written in C

64. Match the List-I with List-II.

List-I (Time domain)

(a) y(t) = x(-t)
(b) x(t) = te^-at u(t), a > 0
(c) y(t) = x(at)
(d) x(t), odd; x(t) = -x(-t)

List-II (Frequency domain)

1
(a + j2πf)²
X(f) = -X(-f)
Y(f) = X(-f)
Y(f) = 1
|a| X(f
a)

Answer: Option B

65. Match the List-I with List-II. Identify the correct combinations.

List-I	List-II
(a) Ion-implantation	I. HRP-206
(b) Lithography	II. Ohmic Contact
(c) Metallization	III. TAB
(d) Packaging	IV. Nuclear Stopping

Choose the correct answer from the options given below:

	(a)	(b)	(c)	(d)
A.	II	IV	III	I
B.	IV	I	II	III
C.	IV	I	III	II
D.	II	III	IV	I

Answer: Option B

66. The most important requirement of an effective metallization scheme in VLSI is that metal must adhere to the silicon in the window and to the oxide that defines the window. In this respect, which of the following metals is unlikely to be used directly on SiO₂?

A. Al B. Ti C. Ta D. W

Answer: option D

67. In crystal growth, the doping concentration in the crystal C_s is given by:

C_s = K_eC_o (1 - M/M_o)^K_e-1

where
K_e = equilibrium segregation coefficient
C_o = initial doping concentration in the melt
M_o = initial weight
M = Weight of the grown crystal
As crystal growth progresses, the composition initially at K_eC_o will increase continually for:

A. K_e < 1 B. K_e > 1 C. K_e = 1 D. K_e = 0

Answer: option A

68. Match the List-I with List-II.

List-I (Interrupt)	List-II (Address (HEX))
(a) IE0	I. 0003
(b) IE1	II. 000B
(c) TF0	III. 0013
(d) TF1	IV. 001B

Choose the correct answer from the options given below:

	(a)	(b)	(c)	(d)
A.	I	II	III	IV
B.	III	II	I	IV
C.	I	III	II	IV
D.	I	IV	II	III

Answer: Option C 69. (B) 70. (C)

71. The default offset register for code segment register (CS) in 8086 is:

A. SP B. DI C. IP D. BX

Answer: Option C 72. (C)

73. For SCR

(a) I²t rating of the SCR represents the capability to withstand the overload current for the specified time, where the current (I) is the rms value for the time interval t.
(b) The negative gate bias decreases the forward blocking capability and maximizes the false triggering possibility during high dv/dt operation.
(c) Resistance at the gate increases the dv/dt capability and lowers the turn-off time.
(d) The gate non trigger voltage is the maximum DC gate voltage that maybe applied between gate and anode for which the device can maintain its rated blocking voltage.
(e) The turn-off time becomes shorter due to introduction of Au Atoms in silicon, which serve as 'traps' for carriers, but it increases ON state loss.

A. (a) and (b) only
B. (b) and (c) only
C. (a) and (d) only
D. (c) and (e) only

Answer Option: D 74. (D) 75. (C)

76. If a coil draws 0.5 A from a 120 V, 60 Hz source at a 0.7 lagging power factor, then

(a) Coil resistance is 240 Ω
(b) Power factor angle is cos^-1 (0.7)
(c) Coil impedance is 168 + j171.4 Ω
(d) Power factor angle is 32.38°
(e) Coil induction is 0.455 H

A. (a) and (b) only
B. (c) and (e) only
C. (d) and (e) only
D. (a) and (e) only

Answer: Option B

cos(phi) = R / Z

or, 0.7 = R / 240 (120/0.5=240)

or, R = 168

XL = sqrt(Z^2 - R^2) = sqrt(240^2 - 168^2) = 171.5 ohm

L = XL/2-pi*f = XL/2*3.14*60 = 171.5/2*3.14*60 = 0.455 H

77. During the oxidation process, which of the following statements is not correct?

A. The rate constant for wet oxidation of silicon increases with decreasing temperature.
B. The wet oxidation is governed by the equation Si + 2H₂O → SiO₂ + 2H₂
C. For a growth of an oxide of thickness 'd', a layer of silicon with thickness of 0.44d is consumed.
D. During the oxidation process, the Si - SiO₂ interface moves into silicon.

Answer: Option C

78. Arrange the following Antennas on the basis of increasing order of directivity

Short dipole HPBW – 90°
λ/4 monopole
Isotropic (hypothetical)
Hemispherical radiator
λ/2 monopole

A. (b), (d), (c), (a), (e)
B. (e), (b), (d), (a), (c)
C. (c), (d), (a), (b), (e)
D. (d), (c), (a), (e), (b)

Answer: Option C

79. (C)

80. In data communication, MODEM:

The word MODEM is contraction derived from words Modulation and Demodulation
MODEM is an interface between digital terminal equipment to analog communication facilities
A MODEM transmitter is analog-to-digital converter (ADC)
The output of a MODEM is, a digital signal carrying analog information

A. (a), (b) and (c) only
B. (b), (c) and (d) only
C. (a) and (b) only
D. (a) and (d) only

Answer: Option C

81. Which of the following statements are correct about the basic transistor amplifier configuration?

The voltage gain of CB amplifier is higher than the voltage gain of CC amplifier
The CB amplifier has low input impedance and a low current gain
The CC amplifier has high input impedance and a low current gain
The CC amplifier has low output impedance and a high current gain
The CC amplifier has low input impedance and a low current gain

A. (a), (b) and (d) only
B. (a), (b) and (c) only
C. (a), (b) and (e) only
D. (a) and (b) only

Answer: Option A

82. Which of the following statements are correct when effective mass of an electron is taken into consideration:

(a) The electron effective mass is independent of the semiconductor properties.
(b) Electrons near top of the V.B. have negative effective mass
(c) The C.B. electron effective mass has a strong dependence on the value of bandgap
(d) The effective mass decreases as the bandgap increases.

A. (a) and (c) only
B. (a) and (d) only
C. (b) and (c) only
D. (b) and (d) only

Answer: Option C

83. The Doppler frequency seen by a stationary radar with a (CW) transmit frequency of 5 GHz and target radial velocity of 100 km/hr is:

A. 387 Hz

B. 256 Hz

C. 428 Hz

D. 927 Hz

Answer Option D Solution doppler frequency = 2*v/λ =2*(100*5/18) / (3*10^8/5*10^9) = 927 (approx) 84. (C)

85. Which of the following statements are correct?

(a) Light Dependent Resistors (LDRs) are based on Photo conductive Effect.

(b) In LDRs, resistance increases from its dark resistance value with increase in light intensity.
(c) LDRs are slow responding to changes in light intensity.
(d) Photodiodes can be operated only in the photoconductive region.
(e) Photodiodes have a faster switching time than Photo-transistors.

A. (a), (c) and (d) only
B. (a), (b) and (c) only
C. (a), (b) and (e) only
D. (a), (c) and (e) only

Answer: Option D

86. In case of Avalanche Photo Detector (APD)

(a) APD is more sensitive than PIN photo diode
(b) APD is a PIN structure
(c) A high electric field intensity is required in APD
(d) There is less noise generation in APD as compared to PIN photo diode

A. (a) and (b) only
B. (b) and (c) only
C. (a) and (d) only
D. (a) and (c) only

Answer; Option D

87. Match the List-I with List-II. Breakdown Electric fields in the following materials:

List-I (Name of the material)	List-II (Breakdown Electric field (V/cm))
(a) GaAs	I. 10⁵
(b) SiC	II. 4 × 10⁵
(c) Si₃N₄	III. 2.3 × 10⁶
(d) Ge	IV. 10⁷

Choose the correct answer from the options given below:

	(a)	(b)	(c)	(d)
A.	II	III	I	IV
B.	II	III	IV	I
C.	IV	II	III	I
D.	IV	I	III	II

Answer: option B 88. (B) 89. (B)

90. The 8-bit stack pointer (SP) register is used by the 8051 to hold an internal RAM address that is called the top of the stack. When the 8051 is reset, what is the value of SP?

A. 00 H
B. 07 H
C. 20 H
D. FF H

Anwer: Option B

91. Telephone Traffic in measured:

A. with Echo cancelers
B. by the relative congestion
C. in terms of grade service
D. In Erlangs

Answer: Option D

92. Number of cells in a cluster in hexagonal cellular communication system with i = 3 and j = 2, will be:

A. 7
B. 12
C. 19
D. 24

Answer: Option C solution: i^2+i*j+j^2 = 24

93. GSM (Global systems for Mobile Communication), bands for Phase I and II operates respectively at:

A. 900 MHz and 1800 MHz
B. 900 MHz and 2100 MHz
C. 1800 MHz and 2400 MHz
D. 1800 MHz and 2100 MHz

Answer: Option A

94. To increase the capacity of a cellular system which of the following is used?

A. Cell splitting and cell sectoring
B. Co-channel reuse ratio
C. Honey comb pattern
D. Increase the cluster size

Answer: Option A

95. What will be total capacity of a cellular telephone systems comprising of 10 clusters with 7 cells in each clusters and there are 10 channels in each cell.

A. 70
B. 700
C. 100
D. 7000

Answer: Option B

Solution:

10*7*10=700

96. (C) 97. (B) 98. (D) 99. (A) 100. (D)

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[Solved] UGC NET Electronic Science August 2024 Question Paper with Answer Key & Detailed Solutions

UGC NET Electronic Science August 2024 Question Paper with Answer Key and Detailed SolutionsDownload Question Paper

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26. Match the List-I with List-II (8051 Timer Modes)

27. Shannon Capacity

28. Satellite Bands

29. EEG & ECG Matching

30. Superheterodyne Receiver Sequence

31. Thyristor Matching

32. Segregation Coefficient Order

33. Counter Valid States (4-bit)

34. Series RLC Impedance Order

35. Open Loop vs Closed Loop Systems

Finding Minterms for the Boolean Expression

1. A'C'

2. A'D

3. A'B

4. BD

List-I

List-II

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UGC NET Electronic Science August 2024 Question Paper with Answer Key and Detailed Solutions
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