UPTU Previous Year Exam papers
B Tech 4th Semester
Electrical Engineering Materials 2006-07
Note : Attempt all questions.
1. Attempt any four :
(a) What are the imperfections in the crystals? Explain.
(b) What are lattice defects? Explain :
(i) Point defects
(ii) Line defects.
(c) Write short notes on :
(i) Miller Indices
(ii) X-ray crystellography.
(d) Calculate C/a ratio for an ideally close packed HCP crystal.
(e) Draw diagrams giving energy band structure of an insulator and a semiconductor. Explain different in their electrical conductivities.
(f) Write a short note on super conductivity.
2 . Attempt any four parts of the following :
(a) Define reverse saturation current. Explain its temp, dependence.
(b) Derive an expression for conductivity of a semi-conductor in terms of concentration of charge carriers and their mobilities.
(c) Derive an expression showing temp, dependence of conduction electron concentration in n-type semi-conductor
(d) What is hall effect? Explain briefly its applications.
(e) Using drift and diffusion current in a semiconductor, find an expression for continuity equation.
(f) Explain classification of materials based on energy band theory.
3 Attempt any two parts of the following.
(a) What is internal field in solids and liquids? Derive an expression for a Lorentz field given as:
Ei (Lorentz) = E + P/£
/ 6 eo
(b) Discuss theory of spontaneous polarization.
Prove that spontaneous polarization occurs when
(c) Derive an expression for electronic polarizability a of monatomic gas atom.
4. Attempt any two parts of the following :
(a) Derive spontaneous magnetization in ferromagnetic material. Prove that at high temp,
the succeptibility is given by % = ———
1 = 0
C = Nfio p2 / k
(b) What are ferromagnetic and ferrimagnetic materials?Explain and compare their properties.
(c) Iron has a curie temp of 104IK, but it is not magnetic in the absence of magnetic field. Discuss the phenomenon of domain theory.