JNTU B-Tech I Semester Supplementary Examinations Semi-Conductors And Magnetic Materials, February 2008

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JNTU IV B.Tech I Semester Supplimentary Examinations, February 2008

                                                                                        Semi-Conductors And Magnetic Materials

(Metallurgy & Material Technology)

SET-III

 

1. Explain with suitable diagrams the conduction band, valence band and the forbidden band and explain the behavior of conductor, semi-conductor and insulator. Explain the contribution of electrons and holes to electrical conduction.

 

2. (a) Explain the experimental setup for measuring Hall voltage.

(b) What are semi-condctors? How do they differ from conductors? Discuss. Explain about p-type semi-conductors.

 

3. (a) Write down as many as you can the ways in which n-type and p-type semiconductors differ from an intrinsic semi-conductor? Also explain it fully

(b) What do you mean by donor exhaustion? Discuss the donor exhaustion graphically in an impurity semi-conductor.

 

4. (a) At a given temperature the product of electron density and hole density is the same for intrinsic and extrinsic semiconductors? Is the statement true or false? Explain your answer with suitable examples.

(b) Discuss how the resistance of an intrinsic semiconductor varies with temperature. Explain further how such a study could be used to measure the energy gap of the semi-conductor.

 

5. (a) What is super conductivity? Outline the experimental facts about this phenomenon.

(b) Explain about Meissner effect.

(c) Explain the important property changes that occur in materials when they change from normal to superconducting state.

 

6. (a) Explain the origin of diamagnetism in a free atom.

(b) Give a few examples and the uses of high permeability materials.

(c) Define and explain the term.

i. Coercive force

ii. Susceptibility.

 

7. (a) Explain the Neel’s theory of antiferromagnetism.

(b) Draw the B-H curve for a ferromagnetic material and explain it. Identify the retentivity and the coercive field on the curve. Explain the energy loss per cycle.

 

8. (a) Define a soft magnetic material and a hard magnetic material.

(b) What is hysteresis loop? Explain the significance of hysteresis loop. Discuss what type of hysteresis loop does a soft magnetic material have and why?

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