### Electronics and Communication Engineering - Electromagnetic Field Theory MCQs Part 13

1.Whenever a wave is incident on a perfect conductor then the reflection coefficient is

A. 1
B. 0
C. 1 < 180°
D. depend upon η1, η2

2.Which one set of the following Maxwell's equation gives the basic idea of radiation ?

A.
B.
C. Δ . D = r, Δ . B = 0
D.

3.When a wave is incident from the more dense into a less dense medium at an angle equal to or exceeding the critical angle, the wave suffers total internal __________ .

A. reflection
B. refraction
C. transmission
D. none of the above

4.Power gain and directivity related with, Gp power gain, Gd directive gain

A. Gp = η Gd
B. Gd = η Gp
C.
D. Gp = η Gd2

5.Radiation intensity in a given direction is the

A. energy radiated per square metre
B. power radiated per square metre
C. power radiated per unit solid angle in that direction
D. none of the above

6.The capacitance between two spheres, whose separation is very much larger than their radii R, is given approximately as

A.
B. 2pε0R
C.
D. none of the above

7.If ωε is the displacement current factor and s is conduction current density factor then which of the following statements is incorrect?

A. For a lossless dielectric σ = 0
B. For an imperfect dielectric σ = 0
C. For a dielectric ωε >> σ
D. For a semiconductor ωε = σ

8.Parabolic and lens antenna used at

A. microwave frequency
B. medium frequency
C. low frequency
D. high frequency

9.Which of the following statement regarding waveguides is incorrect?

A. At waveguide can be coupled to a coaxial cable
B. At frequencies below the cut off value the wave progresses across the waveguide after total reflections
C. Waveguides are usually air filled hollow conducting metallic tubes for transmitting UHF and microwaves
D. Waveguides can handle large power at UHF and microwaves

10.The potential that appears at a point in space due to the current which caused it is called potential

A. accelerating
B. retardation
C. oscillating
D. lagging the current