NTA UGC NET/JRF Exam, December-2019 (Electronic Science)

Total Questions: 100

31. What is the absolute potential at a point 'p' which is 2 m from a point charge Q = +5µC and the work required to move a + 8 nC charge from infinity to P? Assume ∈ᵣ = 1:

Correct Answer: D. 22.5 KV, 180 μJ

32. If the Poynting vector or power density of a TEM wave = 79.6 W/m² in a loss less medium (o = 0) with ∈ᵣ = 4, then the magnitude of Electric field is:

Correct Answer: C. 122.5 Vm⁻¹

33. Evaluate radiation resistance of a Hertzian dipole as radiating element having length L = 1 m at f = 30 MHz with uniform current distribution:

Correct Answer: D. 8 Ω

34. The fields around an antenna may be divided into two principal regions i.e. Fresnel zone and Fraunhofer zone. If L is the maximum dimension of the antenna and A is wavelength, then radius of the Fresnel-Fraunhofer boundary sphere is:

Correct Answer: C.

35. Standing wave envelope for reflected wave is equal to half the incident wave amplitude (Eᵣ = 0.5Eᵢ). The Voltage Standing Wave Ratio (VSWR) of the wave shall be:

Correct Answer: C. 3

36. The Figure of Merit in DSB-SC system is:

Correct Answer: B.

37. The frequency range for satellite communication is:

Correct Answer: D. 1 GHz - 30 GHz

38. The cladding which surrounds the optical fibre core:

Correct Answer: C. acts to help guide the light in the core

39. A binary data sequence 11001110 is applied to 16-ary PSK modulator system for transmission. The bit duration is 1 µ sec. The transmission bandwidth of 16-ary PSK is:

Correct Answer: C. 0.5 MHz

40. A TDM link has 24 signals and each channel is sampled 8000 times/sec. Each sample is represented by 8 binary bits and it contains an additional bit for synchronization. The total bit rate made from the TDM link is:

Correct Answer: В. 1728 K bits/sec