ELECTRICAL & ELECTRONICS ENGINEERING

ELECTRICAL & ELECTRONICS ENGINEERING

B.TECH EXAMINATION
SEM IV, 2011
UTTARAKHAND TECHNICAL UNIVERSITY

Time: 2 hours

Total marks:50

Section A

Attempt any four question:

1. What are miller indices? Sketch the planes (0 1 1), (1 0 0) and (1 2 1) on FCC crystal.
2. Copper has a FCC structure and its atomic radius is 1.278 A. Calculate the density of copper. Given atomic weight of copper = 63.5.
3. Derive the atomic packing factor for HCP crystal.
4. State Bragg's Law and show how it can be used to determine lattice parameters.
5. Explain with diagrams point, line and surface imperfections.
6. Write a short note on bonding in solids.

Section B

Attempt any two parts of following:

1.  What is meant by relaxation time and mean free path as applied to conduction phenomenon. The resistivity of copper is 1.73 x 10^-8 Ω-m and the average time of collision of electrons is 2.42 x 10^-14s. Find:
   (a) The valence electrons per unit volume
   (b) The electron mobility.
2. Describe briefly the various factors which affect the resistance of a material.
3. Write a short note on superconductivity.

Section C

Attempt any two question:

1. Define electronic polarizability and derive the Clausisus-Mosotti equation for elemental dielectrics.
2. What is meant by polarization in a material? Derive the relation P = e_o(e_r -1)E. Explain the terms with examples:(i) Ferro-electricity(ii) Piezo-electricity

Section D

Attempt any two parts:

1. Define the following terms as applied to magnetic materials:
   (a) Curie point
   (b) Relative Permeability
   (c) Magnetic Susceptibility
   (d) Magnetization
   (e) Magnetic Dipole Moment.
2. Calculate the hysteresis loss in 1 hour in 50 kg of iron if the peak flux density reached is 1.2T and the frequency is 25 Hz. Assume Steinmetz coefficient as 628 J/m³ and density of iron as 7.8 x 10³ kg/m³. What will be the area of B-H curve of this specimen if 1 cm = 12.5 AT/m and 1 cm =0.1T.
3. What are ferromagnetic materials? Mention their features and application.

---------------------------------