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Electrical Engineering Objective Questions { Electromagnetism }

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

93. Range of space wave communication in metres equals, where ht and hr are respectively the heights of transmitting and receiving antennas in metres.
B. 3550 (III 4 hr)
C. 1.23 (ht + hr)
D. 1.23 (ht + hr)

94. If the electric field is f = ? ? ar , in cylindrical co-ordinates, then the work needed to move a point charge Q to a point at twice the radial distance is
A. ?KQ/n2
C. +KQ/n2

95.  In free space E (z, I) = 50 cos (wt ? 0 z) ax (V/m), then the average power crossing a circular area of radius 2.5 m in the plane Z = constant is
A. 65.1 W
B. 32.5 W
C. 130.2W
D. none of the above

96. The intrisic impedancen of a conducting medium for which = 58 MS/m, 1r= 1 at a frequency f = 100 MHz, is
A. 2.14 x 105 L45?S2
B. 1.84 x 10-3 L-45?
C. 3.69 x 10-3 L45?S2
D. 3.69 x 103L-45?

97. A half-wave diople is placed at a distance S = y/2 from the apex of a 90? corner reflector. Find the radiation intensity in the direction (A = 900, =0?), given afeed-point current of 1A.
A. 38.2 W/sr
B. 76.4 W/sr
C. 152.8 W/sR
D. 19.8 W/sr

98.  The depth of penetration of a wave in a lossy dielectric increase with increasing
A. conductivity
B. permeability
C. wavelength
D. permittivity.

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