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ECE :: Electromagnetic Field Thoery

  1. Short-circuited stubs are preferred to open circuited stubs because the latter are

  2. A.
    more difficult to make and connect
    B.
    incapable of giving a full range of reactances
    C.
    made of transmission line with a different characteristic impedance
    D.
    liable to radiate

  3. The induction field of short current element varies as


  4. In binomial arrays the elimination of secondary lobes takes place

  5. A.
    at the cost of directivity
    B.
    at the cost of gain
    C.
    both (a) and (b)
    D.
    none of the above

  6. The characteristic equation of plane wave in E independent of two dimensions y and z is

  7. A.
    B.
    C.
    D.
    none of the above

  8. Q-factor of a transmission line at resonance is


  9. In a medium if ε, μ and σ are constant throughout the medium, then it is known as

  10. A.
    perfect vacuum
    B.
    distributed medium
    C.
    homogeneous medium
    D.
    dielectric medium

  11. The directivity of 20 turn helix having a = 12° circumference equal to one wavelength, will be

  12. A.
    1.8 dB
    B.
    6 dB
    C.
    12 dB
    D.
    18 dB

  13. The velocity factor of a transmission line

  14. A.
    mainly depends on the skin effect
    B.
    is always higher for a solid dielectric than for air
    C.
    mainly depends on the dielectric constant of the material used
    D.
    increases the velocity along the transmission line

  15. For TM waves in a parallel plate waveguide, the minimum attenuation arising from imperfect conductors would occur at a freq. of (fc is the cut off frequency)

  16. A.
    3 fc
    B.
    3 fc
    C.
    2 fc
    D.
    2 fc

  17. __________ acts as a depolarizer in a dry cell.

  18. A.
    ammonium chloride
    B.
    carbon powder
    C.
    manganese dioxide
    D.
    zinc chloride