June 2005 Nr10201 Applied Physics

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Code No: NR10201

I B.Tech Supplementary Examinations, June 2005 APPLIED PHYSICS (For 2001 Batch only) ( Common to Electrical & Electronic Engineering,Electronics & Communication Engineering,Computer Science & Engineering,Electronics & Instrumentation Engineering,Bio-Medical Engineering,Information Technology,Electronics & Control Engineering,Computer Science & Systems Engineering,Electronics & Telematics and Electronics & Computer Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain photoelectric effect and derive an expression for photoelectric current density using Fermi-Divac statistics in metals? (b) State and write the relevance of Blochs theorem for the electron in periodic lattice. 2. (a) Discuss different sources of polarizability and obtain an expression for orientational polazrizability following Boltzman statistics. (b) Calculate the polarizabiltiy of Argon atom if it’s relative permittivity at O 0 Cand one atoms pressure is 1.0004. 3. (a) Explain how quantum theory of paramagnetism leads to the statement that susceptibility varies inversely with temperature. (b) Calculate the relative permeability of a paramagnetic material with 3500 amp.m-1 magnetization and 0.05 web.m−2 flux density. 4. (a) Prove that the position of Fermi level with reference to intrinsic level determines a semiconductor whether it is P-type a n-type. (b) Discuss the ‘Law of Mass Action’ in semiconductors. 5. (a) Discuss the mechanism of ‘Drift and Diffusion’ in semiconductors and derive continuity equations. (b) Briefly explain ‘Quasi Fermi Levels’. 6. (a) Explain the working of semiconductor i. Thermistors and ii. Lasers (b) Detail the occurence of phosphorescence and fluorescence in semiconductors. 7. (a) Write the working mechanism of solar cell and derive an expression for the conversion efficiency in terms of fill factor.

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NR

Code No: NR10201

(b) A solar cell with a short circuit current of 0.4 A has a reverse saturation current of 1.5mA. Calculate its open circuit voltage. 8. Write short notes on any FOUR of the following: (a) dc Josephson effect (b) Laser diode (c) Adiabatic demagnetization (d) Effective mass of electron (e) IC capacitors (f) Ferrites. ?????

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