June 2005 Nr10251 Applied Physics

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Code No: NR10251

I B.Tech Supplementary Examinations, June 2005 APPLIED PHYSICS (For 2000 batch only) (Electrical & Electronic Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain the following terms relating to motion of free electrons: i. relaxation time, ii. collision time and iii. mean free path (b) Describe the ‘free electron model’ of a metal, introduced by Sommerfeld. 2. (a) Discuss with suitable mathematical expressions, the motion of an electron in a periodic potential. (b) How the above theory leads to the concepts of band structure of solids and Brillouin Zones? 3. (a) What is meant by polarization of a dielectric material? Mention the different mechanisms of polarization in a dielectric. (b) Write notes on ferro-electricity. 4. (a) Explain briefly Langevin theory of paramagnetism and Weiss theory of ferromagnetism. (b) Derive an expression for the change in the angular velocity of an electron in an atom of a diamagnetic substance when it is subjected to an external magnetic field and hence explain the origin of diamagnetism. 5. (a) Explain the characteristics of a laser beam. (b) Describe the construction and working of a semiconductor laser. 6. (a) How are ‘superconductors’ classified? Explain their properties. (b) Write notes on the applications of superconducting materials. 7. (a) Give the theory of direct recombination of carriers in semiconductors. (b) Obtain the expression for the decay of minority carriers injected into a semiconductor. 8. Write short notes on the following: (a) IC fabrication (b) Hall effect (c) Photodiodes 1 of 1

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Code No: NR10251 (d) Effedtive mass ?????

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