7/30/2019 r5220405 Electromagnetic Waves and Transmission Lines

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Code No: R5220405 R5II B.Tech II Semester(R05) Supplementary Examinations, December 2010

ELECTROMAGNETIC WAVES AND TRANSMISSION LINES(Electronics & Communications Engineering)

Time: 3 hours Max Marks: 80Answer any FIVE Questions

All Questions carry equal marks

1. (a) State and prove Gauss’s law. Express Gauss’s law in both integral and differential forms.

(b) Discuss the salient features and limitations of Gauss’s law .

(c) Derive Poisson’s and Laplace’s equations starting from Gauss’s law. [6+4+6]

2. (a) State Biot- Savart law

(b) Derive an expression for magnetic field strength, H, due to a finite filamentary conductor carryinga curent I and placed along Z- axis at a point ’P’ on y-axis. Hence deduce the magnetic fieldstrength for the length of the conductor extending from - ∞ to + ∞. [4+12]

3. (a) What is the inconsistency of Amperes law?

(b) A circular loop conductor of radius 0.1m lies in the z=0plane and has a resistance of 5Ω givenB=0.20 sin 103 t az T. Determine the current [8+8]

4. The inner and outer dimensions of a coaxial copper transmission line are 2 and 7 mm respectively. Bothconductor have thickness much greater then δ The dielectric is lossless and the operating frequency is400 MHz. Calculate the resistance per meter langth of the

(a) Inner conductor

(b) Outer conductor

(c) Transmission Line [5+5+6]

5. (a) Explain the significances of Poynting theorem and Pointing vector.

(b) A plane wave traveling in a medium of εr = 1, µr = 1 has an electric field intensity of 100 ×√ π.Determine the energy density in the magnetic field and also the total energy density. [8+8]

6. (a) Explain about attenuation in parallel-plate wave guides. Also draw attenuation versus frequencycharacteristics of waves guided between parallel conducting plates.

(b) A parallel plate wave guide made of two perfectly conducting infinite planes spaced 3 cm apartin air operates at a frequency of 10 GHz. Find the maximum time average power that can bepropagated per unit width of the guide for T E 1andTM 1 modes. [8+8]

7. (a) Definite following terms and explain their physical significance.

i. Attenuation functionii. Characteristic impedance

iii. Phase function, and

iv. Phase velocity as applied to a transmission line.

(b) At 8 MHz the characteristic impedance of transmission line is (40-j2) Ω and the propagationconstant is (0.01+j0.18 ) per meter. Find the primary constants.

[8+8]

8. (a) Explain what is meant by voltage reflection coefficient in a transmission line The voltage reflectioncoefficient due to load connected to a lossless transmission line of characteristic impedance 100Ω and working at 3 GHz is 0.5?450. Assuming the load voltage to be 10 V, calculate the r.m.svoltage and current at intervals of one ?fourth wave length from the load up to a distance 5 cm.

(b) A 75 Ω line is terminated by a load of 120 + j80 Ω . Find the maximum and minimum impedanceson the line. [10+6]

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