Mumbai University Previous year question papers
V Sem Electronics Examination May 2008
N.B. : (1) Question No.1 is Compulsory.
(2) Attempt any four questions from remaining.
(3) Vector notation should be used wherever necessary.
(4) Ass:umptions made should be clearly stated..
1. (a) State Poynting theorem and derive expression for instantaneous POYntingvector.
(b) Give Maxwell’s equations for time varying fields in differential and integral forms for good conductors and good dielectrics.
.(c) For free space prove that the value of intrinsic impedance is equal to 377 O.
(d) \ Derive wave equation for homogeneous unbounded source free medium starting from Maxwell’s equations.
2. (a) Derive the equation for characteristic impedance of the two wire line. Find the characteristic impedance if R
=2 n/m, L =8 nH/m,G =0.5 milli mholm, C= 0.23 pF1m.
(b) Using Smith Chart find the input impedance and reflection coefficient at a point 0.64A from load zL=(75 – j 25)0. Given Characteristic impedance =50 O.
3. (a) Derive the expression~ for the reflection and transmission coefficients in case of reflection from perfect dielectric at (i) Normal incidence (ii) Oblique incidence.
(b) Derive boundary co~ditions for electric and magnetic fields at boundary of two dielectric media.
4. Explain the radiation for a short dipole in free space. Show that the power radiated by dipole is-P=80 n2 12 (dllA )2rms. Hence obtain the expression for the radiation resistance
5. Fbr an electromagnetic wave travelling between a pair ofparallel perfectly conducting planes of infinite extent in y and z directions ;-
(i) Analyse the TErun modes after arriving at field components of TE mode.
(ii) Analyse the TMrun modes after arriving at field components ofTM mode.
(a) Obtain the expression for field components ()f a TE wave propagating through rectangular waveguide.
. (b) What is skin effect? Define skin depth how is it related to the attenuation constant.
(c) What is uniform plane wave ? Explain what is meant by Transverse electromagnetic wave.
7. Write Short notes on :-
(a) Concept of retarded potentials
(b) Surface impedance of conductor
(c) Significance ordisplacement current
(d) Impedance matching using Smith Chart.