**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**

**Answer ALL questions.**

**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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