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ECE :: Electromagnetic Field Thoery

  1. Distilled water at 25°C is characterized by σ = 1.7 x 10-4 mho/m and ε = 78 ε0 at a frequency of 3 GHz. Its loss tangent is (ε = 10-9/36p F/m)

  2. A.
    1.3 x 10-5
    B.
    1.3 x 10-3
    C.
    1.7 x 10-4/78
    D.
    1.7 x l0-4/78ε0

  3. The input impedance of short-circuited line of length l where l < λ/4

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

  5. If the height of transmitting and receiving antenna in a LOS system are 49 meter and a 9 meter respectively then the distance up to which communication may be possible is about

  6. A.
    40 km
    B.
    110 km
    C.
    400 km
    D.
    1100 km

  7. In a line VSWR of a load is 6 dB. The reflection coefficient will be

  8. A.
    0.033
    B.
    0.33
    C.
    0.66
    D.
    3.3

  9. ∇ . = 0 is frequently known as

  10. A.
    continuity equation for steady currents
    B.
    Laplace equation
    C.
    Poisson's equation
    D.
    none of the above

  11. A rhombic antenna is a

  12. A.
    resonant antenna
    B.
    non-resonant antenna
    C.
    coupled antenna
    D.
    none of the above

  13. Which of the following relations is valid?

  14. A.
    ∇ x ∇ x = ∇(∇ . ) - ∇2 A
    B.
    ∇ x ∇ x = ∇(∇ x ) - ∇2 A
    C.
    ∇ x ∇ x = ∇2 A - (∇)
    D.
    none of the above

  15. Diffraction of electromagnetic waves

  16. A.
    may occur around the edge of a sharp obstacle
    B.
    is caused by reflections from the ground
    C.
    arises only with the spherical wave fronts
    D.
    will occur when the waves pass through a large slot

  17. The magnetic field intensity vector of a plane wave is given by (x, y, z, t) = 10 sin (5000t + 0.004x + 30 ), where denotes unit vector in y direction the wave is propagating with a phase velocity.

  18. A.
    5 x 104 m/sec
    B.
    -3 x 108 m/sec
    C.
    -1.25 x 107 m/sec
    D.
    3 x 108 m/sec

  19. A line of characteristic impedance z0 ohms, phase velocity VP = 2 x 108 m/sec and length l = 2 m is terminated by a load impedance zL Ohms. The reflection coefficients at the input end and load end are respectively for a frequency of 50 MHz will be

  20. A.
    1
    B.
    - 1
    C.
    -1
    D.
    2