Total No. of Questions—12] [Total No. of Printed Pages—4+1 Seat No. -142 S.E. (Electrical) (I Sem.) EXAMINATION, 2012 MATERIAL SCIENCE (2008 PATTERN) Time : Three Hours N.B. :— (i) Maximum Marks : 100 Answer three questions from Section I and three questions from Section II. (ii) Answers to the two Sections should be written in separate answer-books. (iii) Neat diagrams must be drawn wherever necessary. (iv) Figures to the right indicate full marks. (v) You are advised to attempt not more than 6 questions. (vi) Your answers will be valued as a whole. (vii) Use of logarithmic tables, slide rule, Mollier charts, electronic pocket calculator and steam tables is allowed. (viii) Assume suitable data, if necessary. Physical Constants : (1) Angstrom Unit (AU) = 1 × 10–10 metres. (2) Dielectric constant of free space (∈0) = 8.85 × 10–12 farad/ metre. P.T.O.
(3) Electron volt (eV) = 1.602 × 10–19 Joules. (4) Permeability of free space (µ0) = 4π × 10–7. (5) Mass of electron (m) = 9.107 × 10–31 kg. (6) Mass of proton (mp) = 1.627 × 10–27 kg. (7) Velocity of light (c) = 3 × 108 metre/second. (8) Charge on electron (e) = 1.601 × 10–19 coulomb. (9) Debye unit = 3.33 × 10–30 coulomb-metre. (10) Boltzmann’s constant (k) = 1.38 × 10–23 Joule degree–1. SECTION I 1. (a) Explain orientation polarization in detail. How is it different than ionic polarization ? (b)  Differentiate between photoconductive and photoemissive cells.  Or 2. (a) Write different materials used for photovoltaic material. Describe its construction and working principle. (b) Differentiate between piezoelectric, ferroelectric and pyroelectric materials. 3.  Write down properties and applications of the following : (i) -142  Paper Press Board 2 
(ii) Sf6 gas (iii) Ceramics (iv) Mica and Asbestos. Or 4. (a) How does breakdown occur in vacuum ? Explain by using any one (b) 5. (a) theory.  Define :  (i) breakdown voltage; (ii) breakdown strength; (iii) Primary ionization; and (iv) Secondary ionization. Differentiate between Soft Magnetic Materials and Hard Magnetic Materials. (b)  Calculate Hysteresis loss in a specimen of iron subjected to a magnetization of 60 Hz. The weight of specimen is 50 kg and its density is 8000 kg/m3. Hysteresis loop area is equivalent 250 J/m3. What will be hysteresis loss of specimen of 40 Hz ? -142  3 P.T.O.
Or 6. Explain with properties and applications Diamagnetism, Para- magnetism, Ferro-magnetism and Ferri-magnetism.  SECTION II 7. (a) Write a short note on thermocouple.  (b) What is a bimetal ? Give  (c) A filament of a 230 V, 60 W lamp is to be constructed. The two applications of bimetal. temperature of the filament is to be 1500°C at 60 W. Resistivity of the filament material at 30°C is 5.3 × 10–6 Ω-cm and temperature co-efficient α30 = 0.005/°C. Calculate the length of the filament at 30°C if its diameter at 30°C is 0.025 mm.  Or 8. (a) Describe the groups into which the materials as electric conductors are divided.  (b) Write a short note on superconductivity.  (c) Give the electrical properties and applications of Nichrome and Tungsten. 9. (a)  What are molecular machines ? Why are molecular machines currently been extensively investigated ? What are different possible applications of molecular machines ? -142 4