Download AKTU B-Tech 2nd Sem 2017-2018 RAS201 Engineering Physics II Question Paper

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Paper Id: 199221

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Sub Code:RAS201

Roll No.

B. Tech.

(Semester-II) Theory Examination 2017 - 18

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ENGINEERING PHYSICS-II

Total Marks:70

Time: 3 Hours

Note: Attempt all Sections. If require any missing data then choose suitably.

SECTION A

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1. Attempt all questions in brief. 2 x 7 = 14
1. Define unit cell and primitive cell.
2. Find out the packing factor for a Simple Cubic structure.
3. What is ionic polarization in dielectrics?
4. What is the origin of magnetization in magnetic materials?

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5. What is the difference between conduction current and displacement current?
6. What do you mean by intrinsic and extrinsic semiconductors?
7. Explain the effect of temperature on electrical resistivity of superconducting materials.

SECTION B

2. Attempt any three parts of the following: 7 x 3 = 21

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1. Derive an expression for Compton shift. Explain the presence of unmodified radiation in Compton scattering.
2. Explain ferroelectricity and piezoelectricity. Give some applications of ferroelectric and piezoelectric materials.
3. Derive the electromagnetic wave equations in free space. Prove that the electromagnetic waves propagate with the speed of light in free space.
4. Show that the Fermi level of an intrinsic semiconductor lies half way between the conduction band and valence band. What will be the position of Fermi level in n-type semiconductor? Explain with a suitable diagram.
5. What are carbon nanotubes? Discuss arm chair, zigzag and chiral single walled carbon nanotubes.

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SECTION C

3. Attempt any one part of the following: 7x1=7
1. Show that in a cubic lattice the distance between successive planes of indices (h k l) is given by d_hkl = a / v(h²+k²+l²) where 'a' is the lattice constant. A substance with FCC lattice has a density of 6250 kg/m³ and a molecular weight of 60.2. Calculate the lattice constant. Given, Avogadro's number is 6.02 x 10²³ per gm molecule.
2. What is Laue's spot in X-ray diffraction? Explain how Bragg's law explained the formation of Laue's spot? Calculate the longest wavelength that can be analyzed by a crystal of spacing 2.82 Å in the second order.
4. Attempt any one part of the following: 7x1=7

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1. Explain dielectric loss. Deduce an expression for dielectric loss and sketch the loss spectrum for a polar material.
2. Distinguish diamagnetic, paramagnetic and ferromagnetic substances. A material has 10 turns per cm of wire wound uniformly upon it which carries a current of 2.0 ampere. The flux density in the material is 1.0 Weber/m². Calculate the magnetization of the material (µ₀ = 4p x 10^-7 weber/amp-meter).
5. Attempt any one part of the following: 7x1=7
1. Derive Maxwell's equations in differential form. Give the physical significance of each equation.
2. Prove that electromagnetic waves are transverse in nature. If the magnitude of E in a plane electromagnetic wave is 377 V/m, determine the magnitude of H in free space.

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6. Attempt any one part of the following: 7 x1=7
1. Find out the probability of occupancy of an energy level by an electron if (i) E < E_F and (ii) E > E_F, where E_F is Fermi energy. Calculate the probability of occupancy of energy level by an electron at 300K which is lying 0.015eV below the Fermi-level.
2. Deduce an expression for the concentration of electrons in the conduction band of an intrinsic semiconductor. A semiconductor rod of 10 mm length and 1 mm² cross-section has been doped with a total of 5×10¹³ donor atoms at room temperature. Calculate the electron and hole densities if the intrinsic carrier density in the semiconductor is 2.4× 10¹⁹.
7. Attempt any one part of the following: 7x1=7
1. Discuss the Meissner effect. Show that perfect diamagnetism and zero resistivity are two independent and essential properties of the superconductor.

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2. Explain superconductivity on the basis of BCS theory. Determine the critical current and current density, which can flow through a long thin superconducting wire of diameter 2 mm if the critical field for the material is 1.2x10⁴ A/m.

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