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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 1
26.
Consider a loss less antenna with a directive gain of + 6 dB. If 1 mW of power is fed to it the total power radiated by the antenna will be
4 mW
1 mW
7 mW
1/4 mW
Answer: Option
Explanation:

6 dB = 10 log10

= 100.6 3.98

Pr = 3.98 mW.

27.
A uniform plane wave is one in which
x = 0
.
and are perpendicular
and lie in a plane
Answer: Option
Explanation:

For uniform plane wave, E and H must be in a plane but perpendicular to each other.

28.
The electric field of the incident wave is , where ω = 3 x 109p and β = 10 p. The electric field of the transmitted wave Et is given by
Answer: Option
Explanation:

In, question, it is not mentioned, about medium; dielectric etc.

Ei = Et + Er

Et = Er

Et = Ei.

29.
A short circuited stub is shunt connected to a transmission line as shown in the figure is, if z0 = 500 ohms, the admittance y seen at the function of the stub and the transmission line is
(0.01 - j 0.02) mho
(0.02 - j 0.01) mho
(0.04 - j 0.02) mho
(0.02 + j 0) mho
Answer: Option
Explanation:

30.
Which of the following should dominant wave have?
Lowest cut off frequency
Highest cut off frequency
No attenuation
No phase shift
Answer: Option
Explanation:

Lowest cut off frequency or highest wave-length in a waveguide gives dominant modes.

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