Biju Patnaik University of Technology 2008-5th Sem B.Tech (B Tech) electromagnetic theory . - Question Paper
BPUT(B Tech) fifth semester electromagnetic theory ques. paper.
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Total number of printed pages - 7 B. Tech CP EE 5307Fifth Semester Examination - 2008 ELECTROMAGNETIC THEORY FuH Marks-70
Time: 3 Hours
Answer Question No ? tvfrieft ts compulsory and any five from the rest
The figures in the nght-hand margin indicate marts,
1. Explain the following ; 2x10
j{a) How is ihe position vector of a point tn cylindrical coordinates related to its position vector in spherical coordinates ?
(b) If a vector field is solenoidal at a given "point in space, does it necessarily follow that the vector field is zero at that point?
P.T.O.
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(C) |
What is dielectric polarization |
Why antennas are used in (he form of an |
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(j) | ||
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fd) |
What is Ihe difference between the conduction and convection currents ? |
array ? |
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2, (a) |
Consider a vector field in a rectangular | |
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(ej |
Why cannot the B field of an infinitely |
coordinate system defined by F(x, y, z) |
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long, straight, current carrying conductor |
= zay< Determine the flux of the vector | |
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have a component in the direction of the |
field out of a dosed cylinder of length 2 m | |
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current ? |
and radius 2 m centered on the z axis | |
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(f) |
What is the relation between vector |
and extended from z = 0 to z = 2. 4 |
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magnetic potential A and the magnetic (b) |
Two pints in a cylindrical coordinate | |
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flux through a given area ? | |
system are P, (2,60D, 5) and (1,30= h 3). | |
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(g) |
Under what circumstances is the net vdtage |
Determine an expression for the vector D |
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around a closed loop equal to zero ? |
directed from P1 to P2. Determine the | |
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How does J3 of a low-loss dielectric |
distance between the two points by | |
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medium compare to that of a lossless |
(r) obtaining J D | and | |
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medium ? |
(it) direct integration. | |
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0) |
What are the physical length of a half |
Also find an expression for unit vectors at |
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wave dipole operating at 100 MHz and |
P, and P?< which are pointed in the | |
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1 GHz ? |
direction of D, 6 | |
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CPEE 5307 2 Contd. CPEE 5307 3 P.T.O. | ||
3. (a) Consider a uniformly charged disk of
radius r. Determine the electric field by first obtaining the potential function, 5
(b) A coaxial cable has two concentric cylinders of radii a and b, a < b, The space between the two cylinders is filled with dielectric of relative permittivities eri for a < r < c and s,a for c < r < b.If the inner cylinder is held at a potential VQ with respect to the outer sphere* determine E and P in the two regions, 5
4. (a) Determine the resistance R of a spherical
capacitor of inner sphere radius a and outer sphere radius b that is filled with a lossy dielectric having material parameters c and e, 5
(b) Given H = - 2 ap within a very long
solid conductor of radiws a. Determine the current density within the conductor. Also, find the magnetic tield external to the conductor, 5
5. (a) A material having a conductivity rr and radius r carrying a direct current I. Determine the net power entering a wire ot length L by integrating the Poynting Vector over the wire surface.. Show directly that this is the power dissipated by the wire resistance. 6
(b) A material having a conductivity o and permittivity is placed in a sinusoidal, time varying electric field having a frequency tt>. At what frequency will the conduction current equal the displacement current ? If a = 1CTzS/m and c = 3([jl determine the frequency, 4
(a) Show Ihat the exaci expressions tor the attenuation and phase consiani can be wrrtlen explicitly as
ti c + t3fl 6 - ij Np / m
p = + t3nr* * ij" rad>m
Where p'wjyi and lan6 = ,
0.
*1C
(b) A 100 MHz uniform plane wave Ravelling i a lossy dielectric (*i, * 1) has the follow* phasor expression for the magnetic field intensity vector H = (1 ay + j 2a,) e-0** e'. Writ complete lime domain expressions for the electric and magnetic field vectors.
m
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7. (a) Consider a dipole antenna of total length 1 lhat is driven by a voltage source at its inpul, Assume the antenna is sufficiently
short sq that the current decreases uniformly from its maximufrvat the centre to zero ai the end points. Derive an expressron for the far Reid electnc field in terms of the input current. 6
(b) Determine the directive gajn and directivity of the elementary magnetic dipole. 4
The conductivity of a homogeneous conducting medium, bounded by 10 cm r 20 cm, 30fl 45 and 30s 60ft is 0.4 S/m. The surface al ==45 is at a ground potential, and the surface at = 30 is at 100 V. Using Laplaces equation, determine the resistance of the medium, neglecting the edge effects. 10
PEE 5307 7
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Attachment: |
| Earning: Approval pending. |
