Indian Institute of Technology Roorkee (IIT-R) 2009-2nd Year B.Tech Biotechnology Material Science (electrical and electronic mateials) - Question Paper
MT-201A Materials Science (Electrical and Electronic Conductivity)
Summary:
This ques. paper covers topics like defects in solids, electrical conductivity and magnetic properties of materials.
MT-201A Materials Scicncc (Electrical and Electronic Materials)
%Ote L Answer any 5 questions. All questions carry' equal marks.
IL Tick on the front page of the answer- book the questions attempted.
UL Answer the questions in the ascending order (Le.Q I, 2,3.....etc).
tv. Start writing every question from fresh page.
1 (a) Draw a neat sketch to indicate the unit cell, a slip plane and a slip direction on this plane for a nickel
crystal with a lattice constant of 0,35167nm. Write the Miller indices for both. For this plane and the direction, calculate the planar and linear atomic density respectively.
(b) Define the termcrystal defect*. Draw a chart to indicate the classification of crystal defects.
2 (a) Write the mathematical expressions to express: i) Nordheims rule and ;
ii) Resistivity-mixture rule for heterogeneous mixtures.
(b) What is Hybridization? Explain the*formation of E-bands in the Si crystal involving-hybridization.
?3 (a) What are degenerate semiconductors? Explain with the schematic energy band diagram for n-typc and p-type semiconductors.
(b) Derive an expression of e* concentration in conduction band of a intrinsic semiconductor.
(c) Be atom has an e configuration of Is12sJ. Although Be atom has a full 2s energy level, solid Be is a metal, why?
J.4 (a) Why do covalent solids have higher polarization/dielectric constants?
(b) What is the significance of real and imaginary parts of relative permittivity r ? Explain with diagrams.
(c) Explain with examples the factors effecting selection of dielectric materials.
fdi Draw the structure of BaTi03 crystal. What are the requirements of ferroelectric materials? Compare the phenomenon of ferroelcclricity with ferromagnetism.
<e> Define piezoelectricity and list its applications giving reasons
3-5 (a) Compare the structure and properties of Type 1 and type 11 superconductors. Describe the design of a wiper conducting solenoid. Explain why perfect conductor is different from a superconductor. What will be the difference in application?
(}4 What is Curie temperature of magnetic material? Explain Barkhausen effect with the help of M-H behavior of a previously unmagnetised polycrystalline iron.
M (*) What is deperming? Describe the magneto cr>stalline anisotropy behavior of iron crystal at room temperature with the help of M-H diagram.
(b) For magnetic steels used in transformer cores, determine the hysterisis power loss/sec of the core in wait. It is seen that the maximum magnetic field is 1.5T with its power factor, n, as 1.6. The applied ac frequency is 60Hz. The material constant K is 150.7. The volume of the core is .0108 m\
How can this hysterisis loss be decreased for the operating transformer?
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