NTA UGC NET/JRF Exam, September-2022 (Electronic Science)

Total Questions: 100

31. A voice signal band limited to 3.4 kHz is sampled at 8 kHz and pulse code modulated using 64 quantization levels. Ten such signals are time division multiplexed using on 5-hit synchronising word. The minimum channel band width will be:

Correct Answer: D. 520 kHz

32. The number of reference patterns in the code book (N), the number of samples in each block (K) and the coded transmission rate in bits per sample (r) are related as:

Correct Answer: D.

33. A graded indexed optical fiber has a parabolic refractive index profile (α = 2). If the fiber has a numerical aperture = 0.22, the total number of guided modes at a wavelength of 1310 nm is given by:

Correct Answer: A. 174

34. In Optical Communication system the Zero dispersion wave length is given by:

Correct Answer: В. 1310 nm

35. An R-L load is connected to a 250 V, 400 Hz step down dc converter. The average load current is 100 A. The load resistance is 0.5 Ohm. The allowed ripple limit is 15%. The minimum value of inductor to limit the maximum ripple current is:

Correct Answer: В. 6.67 mH

36. A thyristor can be fired with dv/dt of 200 V/µs. If the forward breakover current of the device is 5 mA. The value of diffusion capacitance is given by:

Correct Answer: A. 25 pF

37. Which of the following statements is not correct about Electromagnetic Flow meter?

Correct Answer: A. This technique can be used for electrical non-contacting fluids like gases.

38. For an Ionization chamber, If 'S' is ionization density, 'N₀ represents ionizing particles arriving each second, 'L' is active length of Chamber, 'P' is pressure of gas in Chamber and 'e' is the charge of an electron. Then Ionization current is calculated using equation.

Correct Answer: D.

39. Which of the following is not a desirable characteristic of manometer fluid?

Correct Answer: A. It should have high viscosity

40. The Q of an unknown coil using parallel connection measurement method can be calculated using which of the following equations:

Correct Answer: C.