NTA UGC NET/JRF Exam, August -2024 (Electronic Science)

Total Questions: 100

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.

Correct Answer: C. 4.5
Solution:

With a finite open-loop gain A = 45,

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?

Correct Answer: B. 0.05 Vm/N, 309.4 pC/N
Solution:

A piezo material's "charge sensitivity" d (in C/N) can be found directly from the device capacitance and the observed voltage-versus-force relationship. With the given geometry and & = 700, the device capacitance C is approximately Because the transducer develops 40 V for a 10 N force, the charge is
Q = CV ≈ 77.5 × 10⁻¹² F × 40V = 3.1 x 10⁻⁹ C
Hence, the charge per newton is
= 310 pC/N (approximately)
The corresponding "voltage sensitivity" g (in V m/N) is related by g = d/(εₒεᵣ). Numerically, one obtains about 0.05 V m/N. Thus the correct pair is approximately 0.05 V m/N and 309.4 pC/N.

43. The following serial data is applied to the Flip Flop shown below. What will be resulting serial data that appear on the Q output? There is one clock pulse for each bit time, also assume that the Q is initially 0. The right most bits are applied first.

J₁ = 10110110
J₂ = 11011001
K₁ = 10010110
K₂ = 11011011

Correct Answer: A. 011100000
Solution:The JK flip-flop operates according to
the following logic:
• J = 0, K = 0: No change in Q.
• J = 1, K = 0: Q is set to 1.
• J = 0, K = 1: Q is reset to 0.
• J = 1, K = 1: Q toggles.
Given data:
• J = J₁ ∧ J₂, where denotes the AND
operation.
• K = K₁ ∧ K₂.
• Q starts at 0.
The serial data is processed bit by bit starting from the rightmost bit. Applying the input combinations of J and K step-by-step for each clock pulse, the resulting serial data at Q output is 011100000.

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

MOV AХ, 31H
ADD AL, 39H
AAA

Correct Answer: C. 010OH

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

Correct Answer: C.
Solution:

For maximum power transfer, the load resistance Rʟ must equal to source resistance Rₜₕ. The total circuit resistance is therefore Rₜₕ +Rʟ = 2Rₜₕ

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)

Correct Answer: D. (a) and (d) only
Solution:

In the 8086 interrupt vector table:
• Type 0 is the divide-by-zero (divide-error) exception.
• Type 1 is the single-step (trap) intęrrupt, not a "1-byte break."
• Type 4 is the overflow interrupt (triggered by 'INTO').
Hence (a) and (d) are the correct statements.

47. The min terms for the following fₘᵢₙ will be:

Correct Answer: C.
Solution:The given Boolean function is:
To determine the minterms, evaluate the truth table for all combinations of A, В, C, D, where the function evaluates to 1. The minterms correspond to rows where the output is 1.
Converting the truth table results to minterms:

ƒₘᵢₙ = ∑ₘ(0, 1, 3, 4, 5, 6, 7, 13, 15)
Thus, the correct option is C.

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

Choose the correct answer from the options given below:

Correct Answer: B.
Solution:

(Standard T-Carrier Channels):
(a) T1 has 24 channels →III
(b) T2 has 96 channels →I
(c) T3 has 672 channels → II
(d) T4 has 4032 channels → IV
So, (a)→ II, (b) → I, (c) → II, (d) → IV.

49. For an QPSK modulator with an input data

Correct Answer: B. 5 MHz and 5 Megabaud

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

Correct Answer: A. The depletion region must be kept thin to reduce the transit time.
Solution:

Stating that "the depletion region must be kept thin to reduce transit time" is not correct in the general sense required for high quantum efficiency. While reducing depletion-region thickness can indeed lower transit times (useful for high-speed detection), it also reduces photon absorption and thereby lowers quantum efficiency.

A practical design must balance these factors, so (A) is the statement that is not correct among the given choices.