Electronics and Communication Engineering - Electromagnetic Field Theory

1. 

Distilled water at 25°C is characterized by σ = 1.7 x 10-4 mho/m and ε = 78 ε0 at a frequency of 3 GHz. Its loss tangent is (ε = 10-9/36p F/m)

A. 1.3 x 10-5
B. 1.3 x 10-3
C. 1.7 x 10-4/78
D. 1.7 x l0-4/78ε0

Answer: Option A

Explanation:

Loss tangent .


2. 

The input impedance of short-circuited line of length l where l < λ/4

A. inductive
B. capacitive
C. resistive
D. none of the above

Answer: Option A

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.


3. 

If the height of transmitting and receiving antenna in a LOS system are 49 meter and a 9 meter respectively then the distance up to which communication may be possible is about

A. 40 km
B. 110 km
C. 400 km
D. 1100 km

Answer: Option A

Explanation:

Distance = 0.4 [ht + hr] metre.


4. 

In a line VSWR of a load is 6 dB. The reflection coefficient will be

A. 0.033
B. 0.33
C. 0.66
D. 3.3

Answer: Option C

Explanation:

VSWR = 100.6


5. 

The refractive index of E layer at frequency of 81 N

A. 0
B.
C. 1
D. 0.5

Answer: Option A

Explanation:


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