Mumbai University Previous year question papers
V Sem Electronics Examination May 2007
Question No.1 is compulsory.
Attempt any four questions out of remaining six questions.
Figures to the right indicate full marks.
Necessary assumptions should be make and clearly stated.
Assume suitable data wherever needed and justify.
Explain the following:
(a) Electrostatic potential and field
(b) Gauss’s Law
2.(a) A parallel plate capacitor has a dielectric of permittivity E and a volume charge density Pv (t) = Pox ( x – d) ;3 distributed throughout the dielectric volume. Find the potential and electric field intensity everywhere between the plates of the capacitor.
(b) Charge is distributed uniformly along an infinite straight line with density PL’ Develop the ex pression for E at a general point in space.
3.(a) Using Ampere’s Circuital law and the equation of continuity, show that aD.V’ x H = J +- at and explain the concept of displacement current density.
(b) Define characteristic impedance and derive an expressin for it for a two wire transmission line.
4. (a) Derive the boundary conditions for electric and magnetic field vectors at the boundary of two dielectric media.
(b) Write down Maxwell’s equations for time varying fields and arrive at the phasor forms of the equations for sinusoidal time variations.
5. (a) Define poynting vector, explain poynting theorem and prove it.
(b) A radar installation transmits a wave whose magnetic field intensity is AH= Hocos (wt – koz) ax m’ where Ho = 25 AIm and f = 30G1iz. p.mpagation is in free space and z is the vertical direction. Assumingplace wavesand lossless propagation,calculate :
(i) The wave number for the wave .
(ii) The electroc fie!d intensity of the wave in phaspr form.
6.(a) For an electromagnetic wave propagafiing between a pair of parallel perfectly conducting planes of infinite extent in the y and z directions, analyse the TErnnmodes after arriving at the field components for the TE mode.
(b) A plane wave has electric field intensity E with Eo cos (wt – kz) ~ y ~ with Eo = 1000 VIm and f = 300 MHz. For its propagation in free space (Iossless),
(i) Calculate the poynting Vector
(ii) Instantaneous and time-averaged power densities in the wave.
7.Show that the power radiated by a short dipole is p =~01t2 T I~m.s.