MORE IN Engineering Physics 2
AU First Year Engineering (Semester 2)
Engineering Physics 2
December 2012
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 Define drift velocity. How is it different from thermal velocity of an electron?
2 M

2 Define Fermi level.
2 M

3 Write an expression for electrical conductivity of an intrinsic semiconductor.
2 M

4 What are the differences between elemental semiconductor and compound semiconductor?
2 M

5 Every magnetic material has an intrinsic diamagnetism. Explain.
2 M

6 State the use of magnetic levitation.
2 M

7 Define dielectric constant.
2 M

8 Distinguish between dielectric loss and dielectric breakdown.
2 M

9 What is shape memory effect?
2 M

10 What are the different crystalline forms of carbon?
2 M

Answer any one question from Q11 (a) & Q11 (b)
11 (a)(i) List the drawbacks of classical free electron theory.
4 M
11 (a)(ii) Obtain Wiedemann Franz law using the expression of electrical and thermal conductivity and find the expression for Lorentz number.
4 M
11 (a)(iii) The density of Silver is 10.5 × 103 kg/m3. The atomic weight of silver is 107.9. Each silver atom provides one conduction electron. The conductivity of silver at 20°C is 6.8×107 ohm-1 m-1. Calculate the density of electron and also the mobility of electrons is silver.
4 M
11 (a)(iv) Calculate the electric and thermal conductivities of a metal with the relaxation time of 10-14 second at 300 K. The electron density is 6×1026 m-3.
4 M
11 (b)(i) Derive an expression for electrical conductivity based on Quantum theory.
8 M
11 (b)(ii) Write the expression for Fermi distribution function and explain with suitable diagram. How does it vary with temperature?
4 M
11 (b)(iii) Calculate the Fermi energy and Fermi temperature in a metal. The Fermi velocity of electrons in the metal is 0.86×106 m/s.
4 M

Answer any one question from Q12 (a) & Q12 (b)
12 (a) (i) Assuming the Fermi-Dirac distribution derive an expression for the concentration of electrons per unit volume in the conduction band of an intrinsic semiconductor.
12 M
12 (a) (ii) Find the intrinsic carrier concentration and position of Fermi energy level I in Silicon with respect to the VB edge. Given mh=0.92 m0; me=0.49 m0; Nc=2.21×1025/m3 Nv=8.60×1024/m3 and T=300 K.
4 M
12 (b) (i) With neat sketches, explain how Fermi level varies with impurity concentration and temperature in both p-type and n-type semiconductors.
8 M
12 (b) (ii) What is Hall effects? Describe an experimental arrangement to measure the Hall co-efficient.
8 M

Answer any one question from Q13 (a) & Q13 (b)
13 (a)(i) Explain the domain theory of Ferromagnetism. Using that theory, explain the formating of hysteresis in ferromagnetic materials.
8 M
13 (a)(ii) The magnetic field strength of Silicon is 1500 A/m. If the magnetic susceptibility is -0.3 ×10-5, calculate the magnetization and flux density in Silicon.
4 M
13 (a)(iii) Differentiate a soft magnetic material from a hard magnetic material.
4 M
13 (b) (i) Explain any four properties of superconductors.
8 M
13 (b)(ii) Differentiate between Type I and Type II superconductors.
4 M
13 (b)(iii) Describe high temperature superconductors.
4 M

Answer any one question from Q14 (a) & Q14 (b)
14 (a)(i) Explain electronic polarization in atoms and obtain an expression for electronic polarizability in terms of the radius of atoms.
10 M
14 (a)(ii) If a NaCI crystal is subjected to an electric field of 1000 V/m and the resulting polarization is 4.3×10-8 C/m2, calculate the relative permittivity of NaCI. Take the value ε0=8.86×10-12 Fm-1.
2 M
14 (a)(iii) The number of atoms in a volume of one cubic meter of hydrogen gas is 9.8×1025. The radius of hydrogen atom is 0.53 Å. Calculate, the polarizability and relative permittivity.
4 M
14 (b)(i) What is meant by Internal field? Obtain an expression for internal field using Lorentz method.
8 M
14 (b)(ii) A solid contains 5 ×1028 identical atoms per m3 each with a polarizability of 2×10-40 Fm2. Assuming that internal field is given by the Lorentz relation, calculate the ratio of internal field to the applied field ε0=8.854×10-12 Fm-1
4 M
14 (b)(iii) The dielectric constant of water is 80. Is water a good dielectric? Is it useful for energy storage in capacitors? Justify your answer.
4 M

Answer any one question from Q15 (a) & Q15 (b)
15 (a)(i) What are shape memory alloys? Describe the characteristics of shape memory alloys.
8 M
15 (a)(ii) List out any four applications of shape memory alloys.
4 M