Bapatla Engineering College::Bapatla (Autonomous) ¼ B.Tech- Short answer model questions Subject: Engineering Physics-II Semester (14PH202) UNIT-I ELECTRON THEORY OF SOLIDS & SEMICONDUCTOR PHYSICS ELECTRON THEORY OF SOLIDS: 1. What is the basic assumption of classical free electron theory? 2. Give any two difficulties or failures of classical free electron theory. 3. What is the basic assumption of quantum free electron theory? 4. Give the allowed discrete energy values of an electron in a one dimensional potential well of infinite height? 5. What is the shape of the curve between E n versus n for a one dimensional crystal? 6. Define Fermi level E F 7. Define wave vector k? 8. Give the relation between wave vector k and wavelength? 9. Give relation between E n and k? 10. Give the Fermi-Dirac distribution function f(e)? 11. Show graphical variation of Fermi-Dirac distribution function versus energy at various temperatures? 12. Give the Fermi energy equation at absolute zero temperature? 13. What is the average kinetic energy of electron at absolute zero (from Fermi level E F0 ) 14. Give the Fermi energy at absolute T O K and hence average kinetic energy of electron? 15. Give the Fermi energy values in electron volts for the following metals Li, Na, K, Rb, Cs, Cu, Ag, Mg, Al. 16. What is the basic assumption in Kronig-Penney model? 17. Give the mathematical form of a periodically varying potential? 18. What is the approximation followed in Kronig-Penney model? 19. Give the mathematical form for effective mass of electron? 20. What is the significance of factor f k in band theory?
SEMICONDUCTOR PHYSICS 1. Distinguish between insulator, conductor and semiconductor? 2. Classify various types of semiconductor? 3. Give the examples of trivalent and pentavalent elements? 4. Give the methods to energise semiconductors other than electrical biasing? 5. Give energy gap E g values for silicon and germanium? 6. Give the difference between direct and indirect band gap semiconductor and also give one example for each? 7. Give the symbols of PN junction diode and Zener diode? 8. Give the diode equation? 9. Give the cut-in voltages for Si and Ge? 10. Show the I-V characteristics of PN junction diode graphically? 11. Define reverse saturation current? 12. Define thermal potential V T? 13. Why Silicon is preferred in manufacturing of commercial junction diodes? 14. Give the mathematical expressions for the carrier concentrations in P-type and N-type semiconductors? 15. How the Fermi level shifts with respect to doping level and give respective band diagrams? 16. Define specific resistance and mobility and also give respective units? 17. What is the relation between drift velocity and conductivity? 18. Give the expressions for drift and diffusion currents in N-type semiconductors? 19. At which experimental conditions drift and diffusion currents take place in semiconductors? 20. What is the law of mass action and give its importance? 21. Can you give the expression for internal electric field E I in an N-type semiconductor? 22. Can you give the expression for the thermal potential and crystal potential? 23. What is the significance of Einstein equation in semiconductor physics? 24. How can we generate electron-hole pairs in semiconductor? 25. Justify the analogy of equation of continuity with Bernoulli s equation in fluid dynamics?
UNIT-II MAGNETIC, DIELECTRIC AND FERRO-ELECTRIC MATERIALS 1. What are the reasons for the magnetic properties for atom? 2. Give the expression for the orbital magnetic moment l and s? 3. Which is the strongest among spin and orbital magnetic moment? 4. Define Bohr magneton and give its value and units? 5. What is the basic assumption in Weiss theory of ferromagnetism? 6. What are magnetic domains? 7. Can you give expression for the effective Weiss field H E? 8. Define magnetic induction B, magnetization M? 9. What is meant by spontaneous magnetization? 10. Define Curie s temperature T C? 11. Define permeability and susceptibility χ? 12. Give the Curie-Weiss law of ferromagnetic substance? 13. Give the values of Weiss field and magnetization values for Iron? 14. Give the technical magnetization curve (B-H curve) for initially demagnetized ferromagnetic substance? 15. Can you see the Hysteresis behavior in a paramagnetic material? Give respective reason. 16. Define coersivity H C and retentivity or remanence B m? 17. What is the physical significance of area under Hysteresis curve (Hysteresis loss)? 18. Give the significance of energy product (BH) m and give its unit? 19. Can you give Steinmetz relation between energy loss and retentivity of ferromagnetic substance? 20. What is the basic difference between soft and hard magnetic materials? 21. Can you give examples for soft and hard magnetic materials? 22. Give ant two applications for each of soft and hard magnetic materials? 23. Give the examples of ferrite materials? 24. What is anti-ferromagnetism? 25. How Curie-Weiss law change for anti-ferromagnetic substance? 26. Distinguish between anti-ferromagnetic and ferrimagnetic substance? 27. What is the range of electrical resistivity for ferrites?
28. Why ferrites are preferred in magnetic applications at high frequencies? 29. Give the example of ferrite material to form ceramic permanent magnets? 30. Distinguish between insulator and dielectric material? 31. Define dielectric constant k? 32. Give the examples of dielectric materials? 33. Define permittivity (ε) and electrical susceptibility (χ)? 34. Define electrical polarization P? 35. What is depolarizing field? 36. What is the Lorentz field? 37. Define internal field local field in a dielectric material? 38. What is the relation between dipole moment and local field? 39. Give Classius-Mossetti relation? 40. Give the types of polarizations and also give respective origin? 41. Show the frequency dependence of polarization graphically? 42. Give examples of Ferro-electric materials? 43. How spontaneous polarization takes place in ferroelectrics? 44. Can all ferroelectrics possess piezoelectric and pyroelectric effects? 45. Why ferroelectrics are preferred in preparation of high energy electrical pulse generators? UNIT-III ADVANCED MATERIALS NANO-MATERIALS: 1. What is nano; give the typical nuclear radius in nanometer? 2. Give few physical and chemical properties of nanomaterial. 3. Give names of some methods for the manufacturing of nanomaterial. 4. Expand HPT and ECAP 5. What is basic principle behind sol-gel technique and give one example? 6. What is meant by compaction? 7. What is basic principle of chemical vapor deposition technique and give diagram of any CVD chamber? 8. What is CNT? 9. What is the basic difference between SWCNT and MWCNT? 10. Give the names of certain nanomaterials and give their uses.
SUPERCONDUCTIVITY 1. Who invented the super conductivity? 2. Define transition temperature (T C ), critical magnetic field (H C ) and critical current (I C ). 3. Give examples of superconducting materials with respective transition temperatures. 4. Define Meisner s effect. 5. Write magnetization curves for type-i and type-ii superconductors. 6. Which Maxwell s equation was contradicted by Meissner effect? 7. What is the vortex state in type-ii superconductors? 8. Give some examples of type-i and type-ii superconductors. 9. Give the names of some high T C superconductors. 10. What is the sign of magnetic susceptibility in a super conductor? 11. What are Cooper pairs? 12. What is the resultant spin of a Cooper pair and which statics does it obey? 13. In which year Bardeen, Cooper and Schrieffer awarded the Nobel Prize? 14. What is the range of binding energy for Cooper pairs? 15. What are phonons? OPTO-ELECTRONIC DEVICES: 1. What is solar cell? 2. Why P-type layer is made so thin in a typical solar cell? 3. Define open circuit voltage and short circuit current in solar cell. 4. In which region carrier generation is take place in solar cell? 5. What is the significance of fill-factor or efficiency of a solar cell? 6. What is photo diode? 7. What is dark current in photo diode? 8. What is LED? 9. Give the difference in biasing of photo diode and LED in electrical circuit. 10. Give some examples of LED materials. 11. Give the circuit symbols for Photo diode, Solar cell and LED. 12. What are Liquid crystals? 13. What are physical and chemical properties of liquid crystals? 14. What are types of liquid crystals?
15. Give some examples of liquid crystal materials? 16. Can liquid crystals produce their own light? 17. What is electroluminescence? 18. Give few differences between LED and liquid crystals. UNIT-IV ANALYTICAL TECHNIQUES NUCLEAR TECHNIQUES: 1. What is radioactivity? Give different units of radioactivity. 2. Define isotopes and give some examples. 3. Give the properties of α, and -rays. 4. Give names of some radio isotopes and their uses in engineering and medicine. 5. Which is quenching agent in GM counter? 6. Define and give the typical values of dead time, recovery time and paralysis times in GM counter. 7. What is the basic principle in GM counter? 8. Give the names of different gasses filled in GM counter. 9. What is the significance of operating voltage in GM counter? 10. Why we can t detect α- particles with GM counter? 11. Define fluorescence and phosphorescence? 12. What is the basic principle of scintillation counter? 13. Why scintillation counter should be protected from external radiation? 14. What is the role of dynodes in Scintillation counter? 15. What are photons? ULTRASONICS 1. Define ultrasonics, infrasonic and audible range. 2. Give few methods to produce ultrasonics. 3. What is the typical speed of ultrasonics in air? 4. Justify whether ultrasonics are longitudinal or transverse? 5. Among solid, liquid and gaseous phase, in which phase ultrasonics move with great speed? 6. What is SONAR? 7. Give few applications of ultrasonics.
MEDICAL APPLICATIONS: 1. What is the role of ultrasonics in cardiology? 2. How can we use ultrasonics in neurology? 3. What is meant by ultrasonic imaging? 4. Can you give few merits and disadvantages of X-ray and ultrasonic imaging in medicine? 5. List different imaging modes in ultrasonic sonography. 6. List basic techniques used to achieve better sensitivity of echo in ultrasonic imaging. NDT: 1. What is the importance of non-destructive techniques? 2. Give the basic principle in Pulse-echo technique. 3. What is the basic principle in Time of Flight Detection technique(tofd)? 4. How many transducers are used in Pulse-echo and TOFD? 5. Give few differences between Pulse-echo and TOFD. 6. What are cavitation bubbles? 7. Give typical temperature and pressure at the site of explosion of cavitation bubbles? 8. Can you see the cavitation effect in solid and gases? 9. What is the important advantage of TOFD technique? 10. What are different scan presentations in TOFD technique? STRUCTURE DETERMINATION: 1. Define primitive cell in crystal lattice? 2. Define translation vector? 3. What is basis? 4. Define interatomic and interplanar spacing. Do both are same? 5. What are Miller indices? 6. Give relation between (h,k,l) and inter-planar spacing (d) in a cubical crystal? 7. What is Brag s law? 8. Give typical values of X-ray wavelength and inter-atomic spacing in NaCl crystal? 9. Why X-ray radiation is preferred to study diffraction in crystals? 10. Give names of some crystal structure determining methods with X-rays. 11. What is the importance of powder diffraction method? 12. What is the importance of shape of photographic film in powder diffraction method? Compiled by Dr.Ch.Anjaneyulu, department of Physics, Bapatla engineering college, Bapatla.