LOYOLA COLLEGE (AUTONOMOUS), CHENNAI –600 034
B.Sc., DEGREE EXAMINATION – PHYSICS
FIRST SEMESTER – NOVEMBER 2004
PH 1500/PHY 500 - PROPERTIES OF MATTER AND THERMAL PHYSICS
01.11.2004
1.00 - 4.00 p.m.
Max:100 marks
SECTION - A
Answer ALL the questions.
(10 x 2 = 20 marks)
1. Two spheres of masses 10 kg and 20 kg are 500 cm apart. Calculate the force of
attraction between the masses.
2. State Hooke's Law. Give the dimensional formula of modulus of elasticity?
3. Define the coefficient of viscosity of a liquid. What is the effect of temperature upon it?
4. Calculate the excess of pressure inside a soap bubble of radius 3 x 10-3m. Surface tension
of soap solution is 20 x 10-3 N/m.
5. Calculate the mean free path of a gas molecule given that the molecular diameter is
2 x 10-10 m and the number of molecules per cubic metre is 3 x 1025.
6. What are intensive and extensive variables?
7. What is Clausius statement of the second law of Thermodynamics?
8. State the conditions required for a reversible process in thermodynamics.
9. What is meant by an equation of State?
10. What is a second order phase transition?
SECTION - B
Answer any FOUR questions.
(4 x 7.5 = 30 marks)
11. a) Derive an expression for the variation of acceleration due to gravity with latitude. (5)
b) How many times faster than the present speed would the earth have to rotate about its
axis, in order that the apparent weights of bodies at the equator be zero.
(2.5)
12. a) Derive an expression for the moment of the couple required to twist one end of a
cylinder when the other end is fixed.
(5)
b) Calculate the elastic energy stored up in a wire originally 5 m long and 10-3 m in
diameter which has been stretched by 3 x 10-4 m due to a load of 10 kg.
(2.5)
13. Derive a general expression for the excess of pressure across a curved liquid surface.
14. Given the equation of state F (p, v, T) = 0, obtain the thermodynamic relation
 P   V   T 

 
 
   1 and hence obtain the coefficient of cubical expansion  for
 V T  T  P  P V
a Van der wall gas.
15. Deduce Maxwell's four thermodynamic relations.
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SECTION - C
Answer any FOUR questions.
(4 x 12.5 = 50 marks)
16. a) Define the three moduli of elasticity and derive the relationship between them.
(9)
b) A rectangular bar, 2 cm in breadth, 1 cm in thickness and 1 m in length is supported at
its middle. Calculate the depression of the young's modulus of the material of the bar
is 2 x 1011 N/m2.
(3.5)
17. a) Derive Poiseuille's formula for the rate of flow of liquid through a capillary tube. (8.5)
b) A capillary tube 10-3 m in diameter and 0.2 m in length is fitted horizontally to a vessel
kept full of alcohol of density 0.8 x 103 kg/m3. The depth of the centre of the capillary
tube below the surface of alcohol is 0.3 m. Viscosity of alcohol is 0.0012 N.S/m2.
Calculate the volume of alcohol that flows in 5 minutes.
(4)
18. a) Obtain Clausius inequality relation.
(8.5)
b) One kilogram of water at 7oC is mixed with 3 kilogram of water at a temperature of
47oC in a thermally insulated versel. Find the change in entropy of the Universe
(Given Cp of water is 4180 J/kg/k).
(4)
19. Explain Joule - Kelvin experiment and inversion curve and obtain an expression for
Joule - Kelvin coefficient.
20. a) Derive an expression for the coefficient of viscosity of a gas on the basis of kinetic
theory of gases.
(8)
b) How does the coefficient of viscosity of gas depend upon temperature and pressure? (2)
c) The density of nitrogen at atmospheric pressure is 1.25 kg/m3. Find the R.M.S.
velocity of nitrogen molecule.
(2.5)
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