Anna University Chennai 2005 B.E ELECTROMAGNETICS AND RADIATION - Question Paper
Sunday, 24 February 2013 12:35Web
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b.
A particle of mass 40 mg and carrying a charge 5x10-9 C is moving directly towards a fixed positive point charge of magnitude 10-8 C. When it is at a distance of 10 cm from the fixed positive point charge, it has a velocity of 50 cm/sec. At what distance from the fixed point charge will the particle come momentarily at rest ? (7)
Q.3 a. Find the capacitance of an isolated ball-shaped conductor of radius R1 surrounded by an adjacent concentric layer of dielectric with permittivity K and outer radius R2. (7)
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Q.4 a. Define "Biot-Savart Law" and explain its significance. (4)
b. A square frame carrying a current I=0.9 A is located in the identical plane as a long straight wire carrying a current I0=5.0A (Fig.6). The frame side has a length a=8.0 cm. The axis of the frame passing through the midpoints of the opposite sides is parallel to the wire and is separated from it by the distance which is n = 15 times greater than the side of the frame. Find:
(i) Ampere force acting on the frame.
(ii) The mechanical work to be performed in order to turn the frame through about its axis with the currents maintained constant. (10)
Q.5 a. Write down Maxwell's equations in charge free and non-conducting medium and hence derive the wave equations of the electric and magnetic fields in the differential form. (7)
b. Consider a wave, which is propagating in a medium having as permeability and as the permittivity. obtain the ratio of the electric and magnetic field. (7)
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PART I
ans any 3 ques.. every ques. carries 14 marks.
Q.7 a What are the major sources of losses in R.F. transmission Lines? To what extent it would be justified to presume R.F. transmission Lines to be lossless? Derive expressions for Attenuation Constant and Phase Shift Constant for lossless transmission Lines. (10)
b. A transmission Line is to be matched to a antenna with a piece of transmission Line. If the operating frequency is 100 MHz, compute the length of the line needed and also the characteristic impedance of the line from which it is to cut. (4)
Q.8 a. What do you understand by waveguide modes? elaborate dominant modes? Sketch rectangular wave guide mode field configuration for TE10 and TM11 mode. (4)
b. Show that a 1GHz signal cannot propagate TE10 in the mode in a rectangular waveguide having a wall separation of five cm. (5+4)
Q.9 What is broad side array? For the case of the broad side array, derive expression for the subsequent :
(i) the total radiated field in the far region.
(ii) condition for principal maxima.
(iii) conditions for nulls and secondary maxima.
(iv) width of the principal lobe. (14)
Q.10 a. What do you understand by ground wave propagation? explain in detail with the expressions for cross over frequency (fco), electric field at a distance 'd' and the loss factor. (7)
b. Estimate the electric field strength at d = 50 Km from a short vertical monopole radiating over ground with mean conductivity (7)
Q.11 Write short notes on any 2 of the subsequent : (2 x 7)
(i) Smith Chart and its applications.
(ii) Cavity resonator.
(iii) Boundary conditions for electric and magnetic fields.
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| Earning: Approval pending. |
