# Mumbai University Previous year question papers

## VI Sem Electronics Examination June 2009

## Medical Electronics

NB:-

Question NO.1 is compoul~ory.

Attempt any four questions from Q. NO.2 to Q. NO.7.

Use vector notations for vectors.

Nec~ssary assumptions made should be clearly stated.

1. Write down Maxwell’s equation~sin phasor form and derive the wave equation for Electric field.

(b) Exp.lainthe significance of the propagation constant and arrive at expressions for 5

its real and imaginary parts for a uniform plane wave.

(c) Derive Ampere’s circuital law in point form for circuits that include capacitors. 10

2. (a) Derive loundary conditions for field vectors E, 0, 8 and H. 10

(b) State Poynting theorem and derive the expression for instantaneous Poynting vector.

3.(a) Derive expressions for the reflection and transmission coefficients of a perfect dielectric when a plane e.m. wave is incident normally on it.

(b) For free space, show that the intrinsic impedance is equal to 377 ohms. 10

4.(a) Obtain the transmission line equations for a two wire transmission line. Define characteristic impedance of the transmission line. Derive an expression for its characteristic impedance.

(b) A load of impedance ZL = 50-j 1000 is connected to a lossless transmission line of characteristic impedance Zo=1000. The line operates at 300 MHz and the speed of propagation on the line is O.BC.Calculate-

(i) the input admittance at a distance of 2.5 m from the load.

(ii) the input impedance at a distance of 2.5 m from the load. Use Smith chart.

5. (a) For an e.m. wave travelling between a pair of parallel perfectly conducting infinite planes, analyse the TE mode. .

(b) An electromagnetic wave propagates downward from an aircraft and into water at frequency of 10 GHz. Assume water has no loss and a relative permittivity of Neglecting interface effects, Calculate-

(i) the wave no. in air

(ii) the wave no. in water.

6. Show that the power radiated by a dipole is P = BOn2 12

7. Write short notes on :-

(a) Displacement Current

(b) Gauss’s Law

(c) Poisson’s equation

(d) Impedance Matching.