Dr MGR Educational and Research Institute 2009 B.E Model %28EEE%29 %2C PH 231 Materials Science - Question Paper

ans ALL ques.
PART-A (10*2=20marks)
1. describe mean free path of an electron.
2. What is Meissner effect?
3. elaborate Extrinsic semiconductors?Give examples.
4. For an intrinsic semiconductor with bandgap Eg= 0.7eV, determine the position of the Fermi level at 300 K if mh* = 6me*.
5. A magnetic material has a magnetization of 3300 ampere/metre and flux density of 0.0044 Weber/metre*metre. compute the magnetising force and the relative permeability of the material.
6. What is Dielectric loss? How is it measured?
7. discuss colour centres?
8. Why is the shape of LED? How is it measured?
9. elaborate shape memory alloys?
10.What is meant by 2nd harmonic generation in non linear optical materials?
Part-B (16*5=80)
11. Solve Schrodinger wave formula for a particle of mass, m inside a potential well of dimension L and find an expression for the discrete energy of the particle.
12.(a)How does electrical conductivity of intrinsic semiconductor vary with temperature? define a method for determining band gap of a semiconductor.
Or
(b)(1)Explain with a sketch the variation of a fermi level and carrier concentration with temperature in the case of P and N kind conductors for high and low doping level.
(2)Write note on Elemental and compound semiconductor.
13.(a)(1)Describe the structures of ferrite. How is the magnetic moments of ferrite calculated?
(2)The unit cube edge of Fe3O4 is about 0.8 nm and their are 8 Fe++ atoms in the cell. compute the magnetization. For irons the 6 outer electrons have 5 spins in 1 directions and the 6th in the other , giving a net moment of four Bohr magneton.
(b)What is meant by POlarisation of Dielectrics? Derive the relation ranging from Dielectric constant and atomic POlarizability?
14.(a)What is cathodoluminescence? discuss how colour display is found in CRO?
(Or)
(b)Describe in detail the working of liquid crystal as display material. elaborate the 2 various display formats commonly used?
15.(a)What are Nanophase material? How do the Physical properties vary with geometry?
(Or)
(b)What are advantage ceramics ? elaborate their characteristics? Write a note on super conductor ceramics.

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Earning:   Approval pending.