Electronics and Communication Engineering - Electromagnetic Field Theory

41. 

A transmission line is feeding 1 watt of power to a horn antenna having a gain of 10 dB. The antenna is matched to the transmission line. The total power radiated by the horn antenna into the free space is

A. 10 watts
B. 1 watt
C. 0.1 watt
D. 0.01 watt

Answer: Option A

Explanation:

= 101 Pr = 10 watt.


42. 

A parallel polarized wave is incident from air into paraffin having relative permittivity 3, the value of its Brewster angle is

A.
B. 30°
C. 45°
D. 60°

Answer: Option D

Explanation:

Brewster angle θ = tan-1 .


43. 

In a conductor which of the following relations hold good?

A. ∇ x D = r
B. ∇ . D = r
C. ∇ x D = 0
D. ∇ . D = 0

Answer: Option C

Explanation:

Inside a conductor free charge is zero, hence, ∇ x D = 0.


44. 

The radiation resistance of a λ/16 wire dipole in free space will be nearly

A. 1 Ω
B. 3 Ω
C. 13 Ω
D. 30 Ω

Answer: Option B

Explanation:

Rr = 80p2.


45. 

Two identical antennas are placed in the θ = p/2 plane as shown in the figure. The elements have equal amplitude excitation with 180° polarity difference, operating of the far-zone resultant electric field strength normalized with that of a single element, both computed for φ = 0, is

A.
B.
C.
D.

Answer: Option D

Explanation:

Normalised array factor = n cos

where φ is the phase difference.

φ = (βd sin θ cos φ + θ1)

and θ = 90°, φ = 45°