Tuesday, September 1, 2020

Chapter 3 : Electromagnetism- Page 7

Chapter 3 : Electromagnetism

61. Marconi antenna

 
A. has corner spacing of X/2
B. has driven elements only
C. is a wideband antenna
D. is an omnidiretional antenna


... Answer is (D)

 

 
 

62. A square corner reflector is used in

 
A. radio astronomy
B. point-to-point communication
C. TV broadcast
D. all the above

... Answer is (D)

 
 
 

63. An underground ground antenna near the

A. must be horizontally polarized
B. acts as an antenna array.

C. acts a single antenna of twice the hight
D. acts as a reflector

... Answer is (B)

 

 
 

64. The effective electrical length of an antenna is

 
A. equal to its physical length
B. greater than its physical length
C. half its physical length
D. 1/X times its physical length

  ... Answer is (B)

 

 
 
65. Grounded antenna is used for frequencies of
  ...
Answer is (C)

 
 
 

66. Tropospheric scatter is made for communication of frequencies in the range
A.
very high frequencies (VHF)
B. ultra high frequencies (UHF)

C.
low frequencies
D. high frequencies

  ... Answer is (B)

 

 
 

67. The depth of penetration of a wave in a lossy dielectric increase with increasing

A. wavelength
B. permittivity.

C.
conductivity
D. permeability

... Answer is (A)

 
 

68.. A short grounded vertical antenna has a length  ᶩ which is 0.05ƛ at frequency f. If its radiation resistance at f is R ohms, then its radiation resistance at a frequency 2f will be

A. R ohms
B. R/2 ohms
C. 4R ohms
D. 2R ohms

... Answer is (C)

 
 

69. A transmission line whose characteristic is a resistance

A. may not be a lossless line.
B. may not be a distortion less line.
C. must be a lossless line.
D. must be a distortion less line.
 
  ... Answer is (A)

 
 

70. The depth of penetration of wave in a lossy dielectric increases with increasing


A. conductivty
B. permeability
C. wavelength
D. permittivity

  ... Answer is (C)

 

 

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