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ECE :: Electromagnetic Field Thoery

  1. Which of the wave remains unaffected whether it is a day or night?

  2. A.
    Sky wave
    B.
    Ground wave
    C.
    Tropospheric wave
    D.
    Space wave

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  3. Which of the following is not an omnidirectional antenna?

  4. A.
    Log periodic
    B.
    Half-wave dipole
    C.
    Discone
    D.
    Marconi

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  5. The unit of magnetic flux density is

  6. A.
    farad/metre
    B.
    ohm/metre
    C.
    tesla
    D.
    ampere/metre

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  7. In a waveguide if TE mode exist for z direction propagation, then

  8. A.
    Ez = 0, Hz ≠ 0
    B.
    Ez = 0, Hz = 0
    C.
    Ez ≠ 0, Hz = 0
    D.
    Ez ≠ 0, Hz ≠ 0

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  9. Critical frequency of a layer in ionosphere

  10. A.
    fc = 9 N
    B.
    fc = 81 N2
    C.
    fc = 81 N
    D.

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  11. Distances near the skip distance should be used for sky-wave propagation

  12. A.
    to avoid the Faraday effect
    B.
    to avoid tilting
    C.
    to prevent sky-wave and upper ray interference
    D.
    so as to exceed the critical frequency

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  13. End fire array has a dipole spacing of λ/2.

  14. A.
    True
    B.
    False

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  15. Which one of following is correct for broadside array?

  16. A.
    Direction of radiation is perpendicular to axis
    B.
    Also perpendicular to the plane
    C.
    Current is fed of equal amplitude equal phase
    D.
    All

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  17. The effective length of an antenna (Le) is

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  19. Curl of gradient A is

  20. A.
    ∇ x (∇A) = 1
    B.
    ∇ x (∇A) = ∞
    C.
    ∇ x (∇A) = 0
    D.
    ∇ x (∇A) = - ∞

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