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### ENGINEERING PHYSICS – II PH2161 ANNA UNIVERSITY SECOND SEMESTER QUESTION PAPER

Friday, January 20, 2012 ·

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.
Common to All B.E./B.Tech.
Second Semester
182202 — ENGINEERING PHYSICS – II
(Regulation 2010)
Time : Three hours Maximum : 100 marks
PART A — (10 ´ 2 = 20 marks)

1. A wire has a resistivity of 1.54 ´ 10–8 ohm-m at room temperature. There are
5.8 ´ 1028 electrons per m3. Calculate the relaxation time.
2. Define fermi energy.
3. Find the resistance at 300K of an intrinsic Ge rod which is 1 cm long, 1 cm wide and 1 cm thick. The intrinsic carrier density at 300K is 2.5 ´ 1019 m–3 and the mobilities of electron and hole are 0.39 and 0.19 m2 V–1 s–1 respectively.
4. State the Hall effect.
5. Give any two properties of hard magnetic materials.
6. What are the properties of superconductors?
7. How does temperature affect electronic and ionic polarizations?
8. An elemental dielectric material has a relative dielectric constant of 12. It contains 28 10 5 ´ atoms /m3. What is its electronic polarizability if Lorentz field is assumed.
9. Mention any two applications of metallic glasses.
10. What are shape memory alloys?

PART B — (5 ´ 16 = 80 marks)

11. (a) (i) State the postulates of classical free electron theory of metals. (8)
(ii) Obtain the expressions for electrical and thermal conductivities and hence prove Wiedemann-Franz law. (8)
Or
(b) (i) Explain Fermi distribution function. (4)
(ii) Obtain an expression for the Fermi energy at T = 0K in a good conductor and hence the average energy of an electron. (12)
12. (a) (i) Obtain an expression for the intrinsic carrier concentration in an intrinsic semiconductor. (12)
(ii) Show that the Fermi level is exactly at the middle of the forbidden energy gap of an intrinsic semiconductor at T = 0K. (4)
Or
(b) (i) Obtain an expression for the carrier concentration in a n – type semiconductor. (12)
(ii) How conductivity varies with temperature in an n-type extrinsic semiconductor? (4)
13. (a) Describe the ferromagnetic domain theory in detail. How does it account for hysteresis phenomenon? (16)
Or
(b) (i) Distinguish between Type I and Type II superconductors. (8)
(ii) Explain the Meissner effect. (4)
(iii) State and explain any two applications of super conductors. (4)
14. (a) (i) Obtain an expression for the internal field inside the dielectric. (12)
(ii) Deduce Claussius – Mosotti equation from local field expression for a dielectric having contribution due to electrical polarizability alone. (4)
Or
(b) Write a note on :
(i) Space charge polarisation. (8)
(ii) Dielectric break down. (8)

15. (a) (i) What are nanomaterials? Describe any two methods of production of nanomaterials. (8)
(ii) Discuss atleast two important applications of nanomaterials. (8)
Or
(b) Write a note on :
(i) Shape memory alloys. (8)
(ii) Carbon nanotubes. (8)
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