Electrical Engineering Objective Questions { Electromagnetism }

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113. The velocity factor of a transmission line

A. depends on the dielectric constant of the material used

B. increases the velocity along the transmission line

C. is governed by the skin effect

D. is higher for a solid dielectric than for air.

114. Short-circuited stubs are preferred to open-circuited stubs because the latter are

A. more difficult to make and connect

B. made of a transmission line with a different characteristic impedance

C. liable to radiate

D. incapable of giving a reactances.

115. Waveguides are used microwave signals because

A. they depend on propagation which microwaves only

B. losses would be too heavy at lower frequencies

C. there are no generators powerful enough to excite them at lowe frequencies

D. the would be too bulky at lower frequencies.

116. Which of the following equations represents the Gauss' law in a homogeneous isotropic medium.

A. D . ds = JJJ pdV

117. A transmission line whose characteristic impedance is a pure resistance

A. must be a lossless line

B. must be a distortionless line

C. may not be a lossless line

D. may not be a distortion less line.

118. Consider a transmission line of characterisitc impedance 50 ohm. Let it be terminated at one end by + j50 ohm. The VSWR produced by it in the tramission line will be

119. Medium wave radio signals may be received at far off distance at night because

A. radio waves travel faster at night

B. ground wave attenuation is low at night

C. the sky wave is stronger at night

D. their is no fading at night

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