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ECE :: Electromagnetic Field Thoery

  1. After reflection from a plane conducting surface, the apparent velocity of electromagnetic wave becomes greater than the velocity of light in free space is called

  2. A.
    conventional velocity
    B.
    phase velocity
    C.
    propagation velocity
    D.
    group velocity

  3. In a turnstile antenna the crossed dipoles are excited with voltages

  4. A.
    in phase with each other
    B.
    90° out of phase with each other
    C.
    120° out of phase with each other
    D.
    180° out of phase with each other

  5. Consider the following; for a loss-less transmission line we can write,

    1. Zin = - jz0 for a shorted line with l = λ/8
    2. Zin = ± j ∞ for a shorted line with l = λ/4
    3. Zin= jz0 for an open line with l = λ/2
    4. Zin = 0 for a matched line of any length
    Select the correct answer using the codes given below codes.

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

  7. Strip lines are used at

  8. A.
    microwave frequency
    B.
    low frequency
    C.
    High frequency
    D.
    at any frequency

  9. In end fire array the principle direction of radiation

  10. A.
    is perpendicular to the array axis
    B.
    is perpendicular to the array axis and also to the plane containing the array elements
    C.
    coincides with the direction of the array
    D.
    is at 45° to the direction of array axis

  11. The gain of an half wavelength antenna is

  12. A.
    2.15 dB
    B.
    10 dB
    C.
    1.78 dB
    D.
    100 dB

  13. Which of the following does not characterize a ferromagnetic material?

  14. A.
    Coercivity
    B.
    Permeability
    C.
    Permittivity
    D.
    Reluctance

  15. Solution of Laplace equations, which are continuous through the second derivative, are called

  16. A.
    bessel functions
    B.
    odd functions
    C.
    harmonic functions
    D.
    fundamental functions

  17. The skip distance does not depends upon

  18. A.
    the power transmitted
    B.
    type of wave propagation
    C.
    angle of beaming of the wave
    D.
    frequency of the signal transmitted

  19. Which one of the following statement is correct?

  20. A.
    Both Laplace's (L) and Poisson's (P) equation are non linear
    B.
    L is non linear but P is linear
    C.
    L is linear but P is non linear
    D.
    L, P both is linear