Anna University Chennai 2012-2nd Sem B.E /B.tech /e , ester, , subject code:PH2161, ENGINEERING PHYSICS-ll (regulation 2008) - Question Paper
Question Paper Code : 10472
B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2012.
Second Semester Common to all Branches PH 2161/182202/PH 23/080040002 ENGINEERING PHYSICS II
(Regulation 2008)
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A (10 x 2 = 20 marks)
1. Define mean free path of an electron.
2. Define Fermi level.
3. Find the resistance of an intrinsic Ge rod 1 cm long, 1 mm wide, and 0.5 mm thick at 300 K. For Ge, m 2.5 x 1019/m3, //e-0.39m2 v-1 s-1 and jj.p = 0.19 m2 v-1 s_1 at 300 K.
11. (a)
PART B (5 x 16 = 80 marks)
Question Paper Code : 10472
Deduce mathematical expressions for electrical conductivity and thermal
Question Paper Code : 10472
conductivity of a conducting material and hence obtain
Wiedemann-Franz law. (6 + 6 + 4)
Or
(i) Explain qualitatively the effect of temperature on Fermi function.
(b)
(4)
(ii) Derive an expression for the density of energy states. (8)
(iii) Calculate the number of states per unit volume in an energy interval of 0.01 eV above the Fermi energy of sodium metal. The Fermi energy of sodium at 0 K = 3.0 eV. (Given Plancks constant h = 6.62 x 10-34 Js). (4)
(i) Obtain an expression for the carrier concentration of electrons in an intrinsic semiconductor. (10)
12. (a)
(ii) Starting with the conductivity of charge carriers in an intrinsic semiconductor, describe how will you determine the bandgap of an intrinsic semiconductor. (6)
Or
(i) Explain the phenomenon of Hall effect. (2)
(b)
(ii) Derive an expressions for Hall coefficient for a n-type semiconductor and for p-type semiconductor. Also state how Hall voltage is related. (10)
(iii) A magnetic flux density of 0.5 Wb/m2 is applied from front to back, perpendicular to largest faces of a specimen. A current of 20 mA flows lengthwise and the voltage measured across its width is 37 jSV . The dimensions of the specimen is 12 mm long, 1 mm wide and 1 mm thick. Find the Hall coefficient. (4)
13. (a)
2 10472
(b) (i) Prove that susceptibility of superconductor is -1 and relative permeability is zero. (4)
(ii) Briefly explain the following :
Question Paper Code : 10472
(1) Cryotron (4)
Question Paper Code : 10472
(2) Magnetic Levitation (4)
(3) High Temperature Super Conductors. (4)
14. (a) (i) Define the following:
(1) Dielectric constant, er
(2) Polarizability, a
(3) Polarization vector, P
(4) Electric flux density, D
(5) Electric susceptibility, x
Give also the necessary equations relating the above quantities. (12)
(ii) Calculate the electronic polarizability of an argon atom whose sr 1.0024 at NTP and N = 2.7 x 1025 atoms/m3. (4)
Or
(b) (i) Define internal field. Obtain the expression for internal field using Lorentz method and hence deduce the Clausius-Mosotti equation.
(2 + 6 + 4)
(ii) The atomic weight and density of sulphur are 32 and 2.08 gm/cm3 respectively. The electronic polarizability of the atom is 3.28 x 10 Fm2. If sulphur solid has cubic symmetry. What will be the relative permittivity? Take Avogadro number as 6.023 x 1026, 0 = 8.86 x IO-12 Fnr1. (4)
15. (a) (i) What are metallic glasses? Explain how they are prepared by rapid
quenching method. (2 + 6)
(ii) List out the applications of metallic glasses (4)
(iii) Explain what are the uses of shape memory alloys. (4)
Or
Question Paper Code : 10472
(b) (i) What is fullerene? (2)
(ii) What are the applications of Carbon nanotubes? (4)
(iii) Explain with necessary diagrams the synthesis of nanomaterials using the following methods :
(1) Chemical Vapour deposition (5)
(2) Sol-gel method. (5)
3 10472
|
Attachment: |
| Earning: Approval pending. |
