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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 1
6.
The input impedance of short-circuited line of length l where λ/4 < l < λ/2, is
resistive
inductive
capacitive
none of the above
Answer: Option
Explanation:

l < λ/4, ZL = 0

, if Zd comes +j kZC then inductive,

If Zd comes -j kZC then capacitive.

for 0 ≤ l ≤ 1/4, λ ≤ l ≤ 3λ/4 will be inductive.

7.
A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode.
4 cm
1 cm
2 cm
8 cm
Answer: Option
Explanation:

.

8.
Find the radiation resistance of an antenna of length λ/10 meter?
8 Ω
780 Ω
7.8 Ω
78 Ω
Answer: Option
Explanation:

.

9.
Charge needed within a unit sphere centred at the origin for producing a potential field,
12 pc
60 pc
120 pc
180 pc
Answer: Option
Explanation:

q = 120p coulomb, r = 1 meter.

10.
A rectangular metal waveguide filled with a dielectric of relative permittivity εr = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is
2.5 GHz
5 GHz
10 GHz
12.5 GHz
Answer: Option
Explanation:

for dominant mode.

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