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ECE Objective Questions { Transmission Lines and Waveguides }



71. A transmission line with R = G = 0 has a characteristic impedance that is
A. purely reactive
B. purely resistive
C. purely inductive
D. purely capacitive

72.  A lossless transmission line with Zo = 300 f is excited with a 100 MHz signal. The line is 50 cm long and is terminated in a resistance of 300 f at the load end. If the velocity factor for the line is 2/3, the source impedance for maximum power transfer from source to the line will be
A. 75 SI
B. 300 S2
C. 150 SI
D. none of the above

73. A lossless transmission line is excited by a 200 MHz signal. If the dielectric constant is 2.25, the phase shift constant is
A. 2 71 rad/m
B. TE rad/m
C. 1.5 rad/m
D. none of the above

74. One of the following statements is wrong
A. When a given transmission line is terminated in its characteristic impedance, its input impedance is always equal to the characteristic impedance irrespective of the length of the line in terms of wavelength
B. When a transmission line is terminated in an impedance other than the characteristic impedance, its input impedance varies with length for a givensignal frequency or with frequency for a given length
C. The characteristic impedance of a lossless line is resistive
D. The propagation velocity on the transmission line is inversely proportional to the permittivity of the dielectric used

75. With reference to transmission lines, the normalised load impedance is determined by
A. the product of load resistance and the characteristic impedance of the line
B. dividing the load resistance by characteristic impedance of the line
C. dividing the resistance value by 100
D. none of the above

76. A 50 fl transmission line is terminated in a load impedance of (50 + j 100) a The normalised load impedance is
A. (1 + j 2) C2
B. (2500 + j 5000)0
C. (0.5 +j)
D. none of the above

77. The arcs of circles on smith chart represent
A. normalised resistnace or conductances
B. different values of SWR
C. normalised reactances or susceptances
D. none of the above

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