Electronics and Communication Engineering - Electromagnetic Field Theory

21. 

A (75 - j 40) W load is connected to a co-axial line of z0 = 75ω at 6 MHz. The load matching on the line can be accomplished by connecting

A. a short circuit stub at the load
B. an inductance at the load
C. a short circuit stub at a specific distance from the load
D. a capacitance at a specific distance from the load

Answer: Option B

Explanation:

ZL = 75 - J . 40, ZC = 75 W, f = 6 mHz

Given ZL is capacitive, so proper matching, load must be inductive.


22. 

A plane wave is characterized by the wave is

A. linearly polarized
B. circularly polarized
C. elliptically polarized
D. unpolarized

Answer: Option C

Explanation:

Because, magnitude is different (0.5, 1) and phase is 90°


23. 

The electric field on the surface of a perfect conductor is 2V/m. The conductor is immersed in water with ε = 80 ε0. The surface charge density on the conductor is ((ε0 = 10-9/36p)F/m)

A. 0 c/m2
B. 2 c/m2
C. 1.8 x 10-11 c/m2
D. 1.14 x 10-9 c/m2

Answer: Option D

Explanation:

.


24. 

A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls calculate the phase velocity for dominant mode.

A. 3 x 108 m/sec
B. 5 x 108 m/sec
C. 1.5 x 108 m/sec
D. 9 x 108 m/sec

Answer: Option B

Explanation:

Vg . Vp = C2

where .


25. 

A plane electromagnetic wave travels in dielectric medium of relative permittivity 9. Relative to free space, the velocity of propagation in the dielectric is

A. increased by a factor of 9
B. increased by a factor of 3
C. unchanged
D. reduced by a factor of 1/3

Answer: Option D

Explanation:

.