UPTU Previous Year Exam papers B Tech 4th Semester Electrical Engineering Materials 2006-07

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

Nay ^

eo

(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,

C

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.

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