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ECE Objective Questions { Transmission Lines and Waveguides }

22. The velocity factor of a transmission line
A. is always greater than unity
B. depends on the permittivity of the surrounding medium
C. is least for air medium
D. is governed by skin effect

23. Impedance inversion at radio frequencies may be applied with the help of a/an
A. half-wave line
B. short-circuited stub
C. quarter-wave transformer
D. open-circuited stub

24.  Indicate the FALSE statement.
A. a piece of line X/4 long and shortcircuited at the far end looks like an open circuit and behaves like a parallel-tuned circuit
B. a short-circuit line less than X/4 long behaves like a pure capacitance
C. an open-circuited line less than X/4 long behaves like a purecapacitance
D. a line k12 long an open-circuited at far end behaves like a parallel-tuned circuit

25. Short-circuited stubs are preferred to open-circuited ones because they
A. are easier to make
B. are not liable to radiate
C. have variable matching properties
D. are made of the same transmission line as the one to which they are connected

26. For connecting an unbalanced ecoaxial line to a balanced antenna, we may use
A. a balun
B. double stub
C. directional coupler
D. a slotted line

27. A waveguide behaves as a ___filter.
A. low-pass
B. high-pass
C. band-pass
D. band-elimination

28. The relationship between the phase velocity vp and the group velocity vg in a waveguiae is
A. vP vg = c2
B. vP = Vg
C. vP v8
D. v= 1 = c2/2

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