ANNA UNIVERSITY COIMBATORE
B.E/B.TECH DEGREE EXAMINATION, OCTOBER 2009
PH 080040002-ENGINEERING PHYSICS-II
PART A (10X2=20 MARKS)
1. On the basis of free electron motion in a conducting material explain the resistance to a flow current.
2. Find the drift velocity of free electrons with mobility of 3.5 x 10^-3 m^2/Vs in cu for an electric field of 0.5 V/m
3. What are the main drawbacks of classical free electron theory?.
4. Define the Fermi energy of metals?
5. What is covalent bond? give the structure of a crystal having this bond
6.find the resistance of an intrinsic ge rod of 1 cm long, 1mm wide and 1mm thick at 300k.the intrinsic carrier density is 2.5 x 10^19/m^3 at 300k and the mobilities of electron and hole are 0.39 and 0.19 m^2 V^-1 s^-1.
7. What is effective mass of an electron?
8. Mention any two applications of Hall Effect experiments in semiconductors
9. Define energy product of a magnetic material.
10. How will you differentiate magnetic materials based on their spin alignment?
11.Calculate the critical current for a wire of lead with diameter 1 mm at 4.2 k critical temperature for lead is 7.18 k and Ho=6.5 x 10^4 A/m.
12. What are high temperature semiconductors? give the examples.
13. Define polarizablity of a dielectric. give the expression for orientation polarization.
14. Write a note on temperature dependence of polarization.
15. Calculate the electronic polarizablity of xenon. the radius of xenon atom is 0.158 nm.
16. Define dielectric loss.
17. What are metallic glasses?
18. Mention few the properties of Ni-Ti alloy?
19. List the synthesis methods of nano manterials.
20. Give the applications of carbon nano tubes?
PART B- (5 X 16=80)
21. i. What are the postulates of classical free electron theory?
ii.Derive an expression connecting electrical conductivity and relaxation time..
22. i.What is density of states? Derive an expression for density of states using that
ii.Obtain an expression for Fermi energy of a metal at 0k..
Explain wiedemann-franz law..
23. i.Derive expression for carrier concentration and Fermi energy in a
ii.Explain the variation of Fermi level with temperature and donor impurity
24. i.Give the theory of Hall Effect.
ii.Using Hall Effect how will you determine the electrical conductivity of a
25. i.What are reversible and irreversible domains? Based on that explain the
phenomenon of hysteresis in ferromagnetic materials
ii.Explain magnetic recording and readout of data n floppy disc.
26. i.What are super conductors? Give two examples. Explain their properties..
ii.Discuss the application cryotron.
27. i.Explain the term internal field in solids. Derive and expression for the lorentz field
for elemental dielectrics.
ii.Obtain clausius-mossotti equation for elemental solid dielectrics.
28.i.Discuss the characteristics of shape memory alloys and their applications.
ii.Describe a method for the fabrication of carbon nano-tubes.