Phys 114-final 2005

(B. Sc. Biochemistry) First Semester 2006 Subject: Phys 114 (Physics)

Full Marks: 100 Pass Marks: 45 Time: 3 hours

Candidates are required to give their answers in their own words as far as practicable. The figure in the margin indicates full marks. Group (A) Long Questions (Any three) (3× ×14 = 42) 1. Derive an expression for rise of liquid inside capillary tube on the basis of excess pressure and also due to net surface tension force acting on it. 2. Describe with neat diagram about npn-transistor in common base and common emitter mode with related characteristics. 3. What are the liquid crystals? Discuss the cholesteric phases of liquid crystal. Explain applications of liquid crystals. 4. Write short note on Milky-way galaxy and verify that numbers of stars in Milky –way exceeds 200 billions. Group (B) Short Questions: (Any six) (6× ×7 = 42) 1. Explain about different forces acting on solid – liquid interface. 2. Calculate the work done to break up a drop of mercury of diameter 1.0×10-2m into eight drops; all of the same size. Find the radius of smaller drop.[surface tension of mercury is 0.035Nm-1] 3. Derive an expression for velocity of electromagnetic wave in free space. 4. Describe about B-H curve for hysteresis in magnetism. 5. Define red-shift? State the Hubble’s red –shift law and use it to determine the age of universe. 6. A binary star system has a separation of 30 A.U. and period of 30 years. The first star is 5times farther away than the other star from the centre of mass .Calculate the masses of the two stars. 7. Explain the concept of partial molal properties and chemical potential and derive the GibbsDuhem equation in open system. 8. Define the polarization of light .Give the theoretical treatment of plane polarized, circularity polarized and elliptically polarized light. Group (C) Very Short Questions: (Any eight) (2× ×8 = 16) 1. Detergents are used to clean clothes? 2. Why the excess pressure in a soap bubble is twice the excess pressure in a liquid drop of same radius? 3. Why ends of glass rod becomes round when heated? 4. What are the differences between oscillator and amplifier? 5. What are damped and undamped oscillation? 6. Why rectifier circuit is used? Write about one of the rectifiers in brief. 7. What is white –dwarf? 8. State Kepler’s three laws of planatory motion 9. Define solar constant and solar luminosity. 10. What do you mean by isotropic & anisotropic? 11. Explain the effect of electric and magnetic field on liquid crystals. 12. What is the ordered parameter in liquid crystal? How does it distinguish the liquid crystal from solid and liquid?