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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 2
21.
A vertical wire of 1 meter length carries a current of 1 A at 10 MHz. The total radiated power is nearly
0.13 W
0.88 W
7.3 W
73 W
Answer: Option
Explanation:

P = I2 . R (1)2 . 73 73 watt.

Here, vertical wire will be considered as dipole.

22.
The length of half-wave antenna is at 30 MHz
2.5 meter
5 meter
10 meter
100 meter
Answer: Option
Explanation:

.

23.
For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the characteristic impedance will be
14 Ω
28 Ω
39 Ω
79 Ω
Answer: Option
Explanation:

f = 400 kHz, L = 0.5 mH, C = 0.08 mF

.

24.
Which one of the following statement is not a correct for a plane wave with = 0.5e-0.1x cos (106t - 2x)az A/m?
The wave frequency is 10-6 r.p.s.
The wavelength is 3.14 m
The wave travels + x direction
Wave is polarized in the z direction.
Answer: Option
Explanation:

P = E x H P = EH, θ = 90°

η = 120p = 377 Ω.

25.
Beamwidth (between first nulls) will be for an antenna at 3 MHz with directivity of 100
140°
70°
210°
60°
Answer: Option
Explanation:

.

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