## Electromagnetic Engineering - Dec 2014

### Electronics Engineering (Semester 5)

TOTAL MARKS: 80

TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.

(2) Attempt any **three** from the remaining questions.

(3) Assume data if required.

(4) Figures to the right indicate full marks.

### Answer the following any four:

**1 (a)** What do you understand by conservative field.(5 marks)
**1 (b)** Derive wave equations for time harmonic fields.(5 marks)
**1 (c)** The radiation resistance of antenna is 72Ω and the loss resistance is 8Ω. Calculate its directivity in dB if the power gain is 16.(5 marks)
**1 (d)** Explain the important advantages and drawback of FDM.(5 marks)
**1 (e)** Define critical frequency, MUF and OWF.(5 marks)
**2 (a)** State and Explain Maxwell's equations in differential and internal form for static field.(8 marks)
**2 (b)** A 10 GHz plane wave traveling in free space has an amplitude of E_{x}=10V/m. Find

i) The phase constant

ii) Intrinsic impedance and

iii) The amplitude and the direction of H.(8 marks)
**2 (c)** Explain the operating modes of helical antennas.(4 marks)
**3 (a)** Explain the mechanism of ionospheric propagation. A high frequency radio link has to be established between two points at a distance of 2000 km. On the earth's surface. Considering the height of 200km and critical frequency of 5MHz. Calculate MUF for given path.(8 marks)
**3 (b)** Derive an expression for radiation resistance of an infinitesimal dipole antenna and explain its significance.(8 marks)
**3 (c)** Derive Laplace's and Poisson's equations.(4 marks)
**4 (a)** Find the transmission and reflection coefficients at the boundary for normal incidence. Given that for region 1:?_{r1}=1, &insin;_{r1}=9 and for region 2 is a free space. Consider the perpendicular polarization.(8 marks)
**4 (b)** Derive an expression for vector magnetic potential wave equation.(8 marks)
**4 (c)** Explain the physical significance of the terms α, β and γ related to wave propagation in lossy dielectrics.(4 marks)
**5 (a)** Give the comparison of FDM, FEM and MOM.(8 marks)
**5 (b)** Determine the poynting vector and explain the power flow terms due to the time varying fields.(8 marks)
**5 (c)** The height of monopole antenna is ?/100 what is the radiation resistance.(4 marks)

### Write a short notes on:-

**6 (a)** Boundary conditions for static E and M fields.(5 marks)
**6 (b)** Polarization of waves.(5 marks)
**6 (c)** Antenna parameters.(5 marks)
**6 (d)** Space wave propagation.(5 marks)