2005
1. Define the following terms connected with sky wave propagation: Virtual height, critical frequency, skip distance and Fading.
2. Write the definition of (i) Isotropic antenna, (ii) Beam width. Show that the directive of an elemental antenna is 1.5.
3. Explain the effect of ground on the propagation characteristics of radio wave in the medium and shout wave bands.
4. Why did Maxwell introduce the concept of displacement current? Explain how the vector potential equation was subsequently modified by this concept.
5. What is meant by Magnetic vector potential? How is circularly polarized EM-wave produced?
6. Given E=Ay[10cos(106t-By)], at a point in air ,find H and the pointing vector at that point.
7. State Faraday’s laws of electromagnetic induction and express the same in differential form as used in Maxwell’s electromagnetic field equation.
8. Starting form Maxwell’s field equation in their differential form, prove that the pointing vector gives the power flow per unit area of cross section, at a point in the medium of propagation.
9. Calculate the amplitudes of the reflected and refracted waves in terms of the incident wave amplitude assuming plane monochromatic waves incident normally on the boundary surface between two dielectrics.
10. Starting from the expressions of electrical and magnetic fields due to a short dipole, derive an expression of its radiation resistance.
11. Derive the expression for radiation resistance of elemental dipole antenna.
12. Starting with Maxwell’s equation derive the equation.
∆2E=ЄH∂2E/∂2t +ЄH∂2E/∂2t
For a linear, homogeneous isotropic medium characterized by Є, σ and μ where the symbols have their usual meaning.
13. Show that the ratio of the electrical magnetic magnetic field of a uniform plane wave is a constant depending upon the medium and that the electrical and magnetic fields are perpendicular to each other.
14. A long cylinder of radius a and length L carries a uniform magnetization M parallel to its axis .the cylindrical magnet passes at constant velocity V through a circular ring of slightly larger diameter. Graph the emf induced in the ring as a function of time giving reason thereof.
15. Explain what are meant by
(i) Surface wave
(ii) Ground wave
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