### Anna University - Engineering Physics - 1 - Question Bank - 2011 Edition

UNIT-1 - CONDUCTING MATERIALS
Part – A
1. Define mobility give its unit.
2. Define Drift velocity.
3. What are the drawbacks of classical free electron theory.
4. Define Mean free path.
5. Define Collision Time.
6. Define Electrical Conductivity.
7. Define Thermal Conductivity.
8. State Wiedemann-Franz law.
9. Define Lorentz number.
10. Define relaxation time of an electron.
11. What is Planck’s Hypothesis.
12. State Planck’s radiation – law.
13. Define Compton-effect.
15. Write down Schroedinger time independent and time dependent wave equation with symbol.
16. Give the physical significance of wave function.
17. What are the eigen value and eigen function ?
18. Write Fermi-Dirac distribution formula.
19. Define Fermi level and Fermi Energy with its importance.
20. How does Fermi function varies with temperature
21. What is work function.
22. what are bound and free electron.
23. For Copper the relaxation time is 10-14 seconds. The free electron density is
24. 2 × 1028/ m3. Calculate its electrical conductivity.
25. What is the probability of an electron bring thermally promoted to the Conduction band in silicon (Ec= 1.07 eV) at 25°C ?
26. Give the expression for change in wavelength of a scattered X-ray Photon.
Part-B
1. Derive the electrical conductivity of a metal based on classical free electron theory.
2. Derive the thermal conductivity of a metal based on classical free electron theory.
3. State and Prove Wiedemann-Frantz law.
4. What is Compton effect ? Give the theory of Compton effect and Show that the Compton shift Δλ = h . (1 – cosθ)/m0c.
5. Explain the application of Schrodinger wave equation to a one Dimensional Potential well.
6. Derive Time independent Schroedinger wave equation and hence deduce the time dependent Schroedinger equation.
7. Describe the energy band theory of solids with the help of neat band diagram. Distinguish between metals insulator and semiconductor on the basis of band theory.
8. Derive the expression for Planck’s theory of Black body radiation.
Unit- II - SEMI CONDUCTORS MATERIALS
Part – A
1. What are compound semi conductors ? Give examples.
2. Why do the conductivity of a semi conductor increase with temperature ?
3. What is an intrinsic-semi conductor ?
4. Why do masses of electron and hole vary in semi-conductor ?
5. What is an extrinsic-semi conductor?
6. Define Fermi level in the case of semi conductors. Mention its position in intrinsic and extrinsic semiconductors at 0˚K.
7. Calculate the wavelength of radiation emitted by LED made up of a semi-Conducting material with Band gap energy (Eg) 2.8 eV.
8. What is an N-type semi-conductor? Give example.
9. What is an P-type semi-conductor? Give example.
10. How does the Fermi-level change with temperature in extrinsic semi conductors ?
11. What is meant by band gap in solids ? Mention its units.
12. What is Hall effect.
Part-B
1. Obtain and expression for the carrier concentration in an intrinsic semi conductor. Calculate the intrinsic concentration of charge carriers at 300˚K, given me= 0.12mo,
2. Discuss electrical conductivity of intrinsic semi-conductor and hence derive an expression for the band gap energy.
3. Derive an expression for carrier concentration in an N-type semi conductor (Density of electrons in the conduction band).
4. Derive an expression for the density of holes in the valence band of an P-type semi conductor.
5. Discuss the variation of Fermi-level with temperature in N-type and P-type semi conductors.
6. Discuss the variation of carrier concentration with temperature for N-type and P-type semiconductors.
7. Explain the determination of Hall co-efficient, carrier concentration and mobility of charge carriers of a semi conductor.
UNIT-3 MAGNETIC AND SUPERCONDUCTING MATERIALS:M
PART-A
1. What is magnetic material?
2. Define magnetic Induction give its unit
3. Define magnetic field Intensity give its unit
4. Define free space permeability
5. Define Magnetic permeability
6. Define relative permeability
7. Define Intensity of magnetization
8. What is magnetic susceptibility
9. .What is the relationship between relative permeability and magnetic susceptibility?
10. State any four properties of Dia magnetic substance
11. State any four properties of Para magnetic substance
12. State any four properties of Ferro magnetic substance
13. Define domain
14. Distinguish between Ferro magnetic and antiferro magnetic
15. What is Curie temperature?
16. Define Bohr magnetron
17. Define Magnetic moment
18. Define Hysteresis
19. Distinguish between hard magnetic materials and soft magnetic material
20. Define GMR effect
21. Write a short note on bubble memories
22. Distinguish between RAM and ROM
23. Define Transition temperature
24. Define Super conductivity
25. Distinguish between Type-I and Type-II superconductor
26. What is Meissner Effect?
27. Define Isotope effect
28. What is high temperature superconductor? give example
29. What is SQUIDS?
30. What is magnetic levitation?
31. How are different magnetic materials classified?
32. What are the different sources of permanent magnetic moment?
33. What is curie –Weiss Law?
34. Give the significance of Curie Weiss law
35. What is Heisenberg theory of ferromagnetism?
36. What is meant by Hysteresis loss?
37. Define Energy product of magnetic material.
38. What are the applications of ferrites?
39. Why are ferrites advantageous for use as transformer cores?
40. Explain the importance of the magnetic materials
41. What are the five basic parts of a digital magnetic tape system?
42. How is earth garnets used for data storage?
Part B

Magnetic materials:

• What are diamagnetic and paramagnetic susceptibilities of material? Discuss the temperature variation of their susceptibility.
• Discuss Langevin theory of a paramagnetic gas and obtain an expression for the paramagnetic susceptibility of the gas. What are the main drawbacks of the theory?
• Derive an expression for the magnetic moment M of a paramagnetic solid on the basis of quantum theory.
• What is Ferro magnetism? Explain the reason for the formation of domain structure in ferromagnetic material and how the hysteresis curve is explained on the basis of the domain theory.
• a) Classify the magnetic materials on the basis of their spin.
• b) What are ferromagnetic domains?
• c) Discuss Weiss theory of Ferro magnetism
• D) What are its merits and demerits?
• Give an account of Weiss theory of Ferro magnetism and show from the post of Langevin function spontaneous magnetization exists below the Curie temperature and vanishes above the Curie temperature.
• Explain the domain theory of Ferro magnetism. Using that how will you explain the properties of Ferro magnetic materials?
• Draw a B-H curve for a Ferro magnetic material and identify retentivity and coercitive field on the curve.
• Write an essay on different magnetic storage media. What are their relative merits and demerits?
• · In detail explain how data are stored in magnetic materials. What are the functions of writing and reading heads? How are they designed?
• What are hard and Soft magnetic materials compare their properties Give example.
• Discuss the phenomenon of antiferromagnetism.how does an anti ferromagnetic substance differ from a diamagnetic substances

SUPERCONDUCTING MATERIALS:
• Give the difference between type-I and type-II superconductor.
• Explain the superconducting phenomena. What are its properties? What are in application?
• Write an essay on superconducting materials and its applications. What is the new development?
• What are high Tc superconductors? Give four examples.
• · Explain the following
• · Meissner effect
• Explain the effect of Isotopes on superconductors
• What is SQUID?
• Explain BCS theory with a special note on copper pairs
• Give four medical application of superconductors
• Explain Magnetic levitation
Unit 4 DIELECTRIC MATERIALS:

Part-A
1. Define electric polarization
2. Compare active and passive dielectrics
3. Define electronic polarization.
4. What are the differences between polar and non polar molecules?
5. Define local field.
6. What is meant by dielectric loss and loss tangent? Why it occurs?
7. What is meant by dielectric breakdown and dielectric strength?
8. Explain electrochemical breakdown in dielectric.
9. What are dielectric materials? Give its properties.
10. Define dielectric constant
11. Define polarization vector and electric displacement vector
12. Define Ionic polarizations
13. Define Space charge polarization
14. Define orientation polarization.
15. What is the microscopic polarization mechanism involved in dielectric polarization
16. Compare the electronic and orientation polarization.
17. What is effect of frequency of an a.c field on polarization?
18. What is the effect of temperature on polarization?
19. What are the different breaks down mechanisms that occur in a dielectric material?
20. Discuss the discharge and defect breakdown in dielectrics.
21. What are the ways in which the dielectric breakdown can be minimized?
22. Give any four applications of dielectric in transformer,
23. Write any four applications of dielectrics in capacitors/
24. What is meant by electric susceptibility?
25. List out of frequency dependence of polarization
26. Write a note on temperature dependence of polarization?
Part-B

1. Discuss in detail the various dielectric breakdown mechanisms.
2. Deduce Clausius Mosotti equation and explain its use in predicting the dielectric constant of solids
3. Derive an expression for the orientation polarizability
4. What is meant by polarization in dielectric? Arrive at the relation between the dielectric constant and atomic polarizability.
5. Show that the imaginary part of the dielectric constant accounts for a condenser being lossy.
6. Explain the different types of polarization mechanisms involved in a dielectric material
7. What is meant by local field in a dielectric and how is it calculated for a cubic structure/deduce the clausius Mosotti equation
8. Write a short note on dielectric loss and breakdown mechanism and application of dielectric materials
UNIT-5 MODERN ENGINEERING MATERIALS:

1. What are metallic glasses?
2. What is the advantage of using metallic glasses as transformer core material?
3. Name any four applications of metallic glasses.
4. What are shape memory alloys?
5. What are the merits and demerits of SMA?
6. What are nano phase materials?
7. Name any four methods employed to produce nano phase materials.
8. What is meant by Super plasticity?
9. Define Nano technology
10. Define quantum confinement
11. State any four properties of nano phase materials
12. What are the type’s carbon nano tubes?
13. What is meant by glass transition temperature?
14. What do you understand by the term Quenching?
15. What are the types of Met glasses?
16. Mention any four properties of met glasses?
17. List out any four recent applications of nano materials
18. What is transformation temperature?
19. What do you understand by Martensite and Austenite Phases?
20. Define pseudo elasticity.
21. What are the properties of SMA?
22. What are the types of SMA?
23. Give any four application of SMA.
Part-B
1. What are nano phase materials? Explain how the physical properties vary with geometry
2. Give the concept properties and applications of metallic glasses.
3. Explain the various technique used to prepare nano phase materials
4. How are metallic glasses prepared? Explain how the melt spinner device can be used to produce metallic glasses.
5. Give the properties and applications of nano phase materials
6. What is meant by SMA? Explain its working.
7. Give the characteristics and applications of shape memory alloys.
8. Explain the various techniques to produce carbon nano tubes.
9. Give the properties and application of carbon nano tubes.