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ECE :: Electromagnetic Field Thoery

  1. ZL = 200 Ω and it is desired that Zi = 50 Ω The quarter wave transformer should have a characteristic impedance of

  2. A.
    100 Ω
    B.
    40 Ω
    C.
    10000 Ω
    D.
    4 Ω

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  3. A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing 10 cm. And if each array element feeding with 1 amp. current and operating at same frequency then find the half power beamwidth

  4. A.
    B.
    C.
    10°
    D.
    15°

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  5. Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 1014 Hz in glass. Assume velocity of light is 3 x 108 m/sec in vacuum.

  6. A.
    4 μm
    B.
    3 μm
    C.
    2 μm
    D.
    1 μm

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  7. The function f(x - vot) represent which of the following?

  8. A.
    A stationary wave
    B.
    A wave motion in forward direction
    C.
    A wave motion in reverse direction
    D.
    None of the above

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  9. A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be

  10. A.
    196 W
    B.
    73 W
    C.
    36.5 W
    D.
    18.25 W

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  11. The input impedance of short-circuited line of length l where λ/4 < l < λ/2, is

  12. A.
    resistive
    B.
    inductive
    C.
    capacitive
    D.
    none of the above

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  13. A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls find cut off wavelength for dominant mode.

  14. A.
    4 cm
    B.
    1 cm
    C.
    2 cm
    D.
    8 cm

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  15. Find the radiation resistance of an antenna of length λ/10 meter?

  16. A.
    8 Ω
    B.
    780 Ω
    C.
    7.8 Ω
    D.
    78 Ω

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  17. Charge needed within a unit sphere centred at the origin for producing a potential field,

  18. A.
    12 pc
    B.
    60 pc
    C.
    120 pc
    D.
    180 pc

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  19. A rectangular metal waveguide filled with a dielectric of relative permittivity εr = 4, has the inside dimensions 3 x 1.2 cm, the cut off frequency for the dominant mode is

  20. A.
    2.5 GHz
    B.
    5 GHz
    C.
    10 GHz
    D.
    12.5 GHz

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