Exam Paper

B. Tech. (Third Semester Examination, 2000) (Electrical / Electronics) Material Science Q.1.

(a)

(b) Q.2.

(a) (b)

(c)

Q.3.

Q.4.

(a) (b) (c) (d) (a) (b)

Q.5.

(a) (b) (c)

Q.6.

(a) (b)

Q.7.

(a)

Explain “Space Lattice” and “Bravais’ Lattice “ Draw Bravais’ Lattices corresponding to : (i) Simple Cubic, (ii) Body-centered Cubic, (iii) Face-centered Cubic, (iv) Simple Orthorhombic (v) Base-centered Orthorhombic, (vi) Body-centered Orthorhombic Systems. Draw the planes (100), (110) and (111) in a simple cubic lattice. Define electrical conductivity of metals. Discuss various factors affecting the electrical conductivity. Giving reasons mention one material for each of the following applications: (i) Heating element of a filament lamp, (ii) Electric Heater Element, (iii) Resistor for precision instruments. A uniform silver wire has a resistivity of 1.54 x 10-8 ohm m at room temperature. For an electric field along the wire of 1V/cm and 5.8 x 1028 electrons/m2, calculate the average drift velocity, the mobility and the relaxation time. Distinguish between “Oriental Polarization” and “Ionic Polarization”. Explain “Spontaneous Polarization”. Discuss frequency dependence of the dielectric constant of a solid. What is “Dielectric Loss” ? How does it depend on “Loss tangent”? Explain electrical properties of insulating materials. Discuss the factors which affect these properties. Explain Hall Effect. Derive expressions for Hall Voltage and Mobility assuming all the charge carriers move with mean drift speed. Mention applications of Hall effect. For a P-N junction diode write I-V equation and explain with a diagram the effect of temperature. Explain ‘Avalanche Breakdown’ and ‘Zener Breakdown’ in P-N junction diode. The resistivity of pure germanium at room temperature is 0.47 ohm-m. Find out the current density of germanium at the room temperature for the electron mobility of 0.42 m2/volt-sec and hole mobility = 0.20 m2 volt/sec. Explain concept of ‘Ferromagnetism’ and ‘Magnetic Domain’. Mention properties of ferromagnetic materials and discuss effect of temperature. Explain the term ‘Superconductivity’. Name any two superconducting materials giving at least one application for each. Differentiate between ‘Magnetic Anisotropy’ and ‘Magnetostriction ‘.

(b)

Q.8.

Sketch typical hysteresis loops for soft iron, hard steel and ferrite. On the basis of hysteresis loops discuss the applications of these magnetic materials. (c) What do you understand by rare magnetic materials? Mention any two rare magnetic materials and mention their applications. Write short notes on any THREE of the following: (a) Binary Phase Diagram, (b) Piezoelectricity, (c) Energy Band Theory, (d) Classification of Magnetic Materials.