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Electromagnetics Question Paper - Dec 17 - Electronics And Telecomm (Semester 5) - Pune University (PU)
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Electromagnetics - Dec 17

Electronics And Telecomm (Semester 5)

Total marks: 70
Total time: 150 mins
INSTRUCTIONS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.

1.a. Derive an expression for electric field intensity $\overline{\mathrm{E}}$ at a point $\rho$ due to infinite line charge with uniform charge density $P_{L}$.
(6 marks) 00

1.b. State significance of poisson's and laplace's equations. Derive the expressions for the same
(6 marks) 00

1.c. In cylindrical co-ordinates a magnetic field is given by

$\overline{H}=\left(2 \rho-\rho^{2}\right) \hat{a}_{\phi} \quad \mathrm{A} / \mathrm{m}$ for $0 \leq \rho \leq 1 \mathrm{m}$.

i)Determine the current density as a function of $\rho$ within the cylinder.

ii) Determine total current passing through surface $Z=0,0 \leq \rho \leq 1$ in $\hat{a}_{z}$ direction

(8 marks) 00

OR

2.a. If $\overline{D}=\left(2 y^{2}+z\right) \hat{a}_{x}+4 x y \hat{a}_{g}+x \hat{a}_{z} \quad \mathrm{c} / \mathrm{m}^{2}$ Find.

i)Volume charge density at (-1, 0, 3)

ii)The flux through the cube defined by $0 \leq x \leq 1,0 \leq y \leq 1,0 \leq z$

iii) The total charge enclosed by the cube.

(6 marks) 00

2.b. Derive an expression for capacitance of parallel plate capacitor.
(6 marks) 00

2.c. Derive boundary condition for the interface between two magnetic media of different permeabilities.
(8 marks) 00

3.a. state poynting theorem. State significance of poynting vector. Derive an expression for time average poynting vector
(8 marks) 00

3.b. In free space $\overline{E}=20 \cdot \cos (w t-50 x) \hat{a}_{y} \mathrm{V} / \mathrm{m}$ Calculate

i) $\overline{J} d$

ii) $\overline{H}$

iii) w

(8 marks) 00

OR

4.a. State Maxwell's equations in point and integral form for

i)Static electric and steady magnetic field.

ii) Time varging field.

(8 marks) 00

4.b. State Faraday's law. Explain the terms transformer emf and motional emf.
(8 marks) 00

5.a. State primary and secondary constants of transmission line. Derive relationship between primary and secondary constants of transmission line
(8 marks) 00

5.b. The characteristic impedance of the uniform transmission line is 2040 ohm at a frequency of 800 Hz. At this frequency the propagation constant is 0.054 enter image description here Determine R L, G, C, V and $\mathrm{R} \mathrm{L}, \mathrm{G}, \mathrm{C}, \mathrm{V}$ and $\lambda$.
(10 marks) 00

6.a. What is meant by dissipationless line? Derive an expression for input impedance of dissipationless line.
(8 marks) 00

6.b. A lossless transmission line $\mathrm{Z}_{\mathrm{o}}=50 \Omega$ is 30 $\mathrm{m}$ is 30 m long and operates at 2Mhz . The line is terminated with a load $\mathrm{Z}=60+\mathrm{i} 40 \overline{\Omega}$ . If u = 0.6 C on the line , Using Smith chart find

i) Reflection coefficient

ii) Standing wave ratio

iii) Input impedance

iv) Position of $\mathrm{V}_{\mathrm{max}}$ & $\mathrm{V}_{\min }$ from load

(10 marks) 00

7.a. What is meant by polarization of the wave. State its types and explain any one detail
(8 marks) 00

7.b. Explain the terms :

i) Depth of penetration

ii) Snell's law

(8 marks) 00

OR

8.a. Explain how reflection of wave takes place by perfect conductor
(8 marks) 00

8.b. Calculate skin depth propagation constant and wave velocity v at a frequency of 1.6 MHz in Aluminium where 6 = 32.8 Ms/m and $\mu_{2}=1$
(8 marks) 00

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