Tuesday, September 1, 2020

Chapter 3 : Electromagnetism- Page 5

Chapter 3 : Electromagnetism

41. A transmision line of length nƛ./4 (n is integer) is short circuited at the far end. The input impedance is

 
A. Z₀
B. Z₀/2
C. Zero
D. Infinite


... Answer is (D)

 

 
 

42. A transmission line of length ᶩ < ƛ./4 is open circuited at the far end. The input impedance is

 
A. capacitive
B. resistive
C. inductive
D. Z₀/2

... Answer is (A)

 
 
 

43. A transmission with the load radiates energy

A. in a well defined direction.
B. uniformally in all directions.
C. inside a hollow sphere.
D. uniformally in horizontal plane.

... Answer is (C)

 

 
 

44. To couple a coaxial line to a parallel wire line, it is best to use

A. a directional coupler
B. a quarter wave line
C.
a balun
D. a slotted line

  ... Answer is (C)

 

 
 
45. Radiation resistance of a halfwave dipole is
  ...
Answer is (A)

 
 
 

46. Main drawback of a two hole directional coupler is its
A.
poor directional coupling
B. high standing wave ratio

C.
poor directirity
D. narrow bandwidth

  ... Answer is (D)

 

 
 

47. Power gain GP of an antenna in a given direction is the ratio of

A. average power to maximum power
B. peak power to rms power

C.
radiation intensity in that direction to the average radiated power
D. radiation intensity in that direction to the total input radiated power

... Answer is (C)

 
 

48.. The effect of ground on radiation pattern of an antenna is

A. to produce more number of nulls.
B. to cause concellation of radiation along the ground
C. both and above
D. to change its effective wavelength

... Answer is (C)

 
 

49. Yagi antenna has

A. only a folded dipole
B. driven element, reflector element and several director elements
C. one driven element and one reflector element
D. one driven element and one director element
 
  ... Answer is (B)

 
 

50. A non-resonant antenna is


A.
rhombic antenna
B. log periodic antenna

C.
Yagi antenna
D. folded dipole.

  ... Answer is (A)

 

 

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