Electronics and Communication Engineering - Electromagnetic Field Theory

46. 

Find the noise factor for an antenna at 27°C with equivalent noise temperature 30°K

A. 20
B. 100
C. 300
D. 1.1

Answer: Option D

Explanation:

Te = T0(F - 1)

.


47. 

The displacement flux density at a point on the surface of a perfect conductor is = 2(ax - 3 az)c/m2 pointing away from the surface. The charge density at that point c/m2 will be

A. 2
B. - 2
C. 4
D. - 4

Answer: Option C

Explanation:

∇ . D = r.


48. 

Characteristic impedance of a transmission line is 50 Ω. Input impedance of the open circuited line.
Zoc = 100 + J150 Ω. When transmission line is short circuited, then value of the input impedance will be

A. 50 Ω
B. 100 + J150 Ω
C. 7.69 + J11.54Ω
D. 7.69 - J11.54 Ω

Answer: Option D

Explanation:

ZC = ZOC - ZSC 50 = (100 + j150)(ZSC) .


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