## Download "Statistical Physics and - Physics" Question Paper A PDF of B.A / B.Sc. (General) 4th Semester Previous Years for Students.

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## B.A. /B.Sc. (General) 4th SemesterPhysics Paper A - Statistical Physics and Thermodynamic-II

Time Allowed: Three Hours] [Maximum Marks:

Note: - (1) Attempt five questions in all, selecting two each from Unit I and II. Unit III is compulsory.

(2) All questions carry marks as indicated.

(3) Non-Programmable Calculators are allowed.

(4) Logarithmic Tables can be asked.

UNIT-I

I. (a) Find the relation for the entropy of one mole of an ideal gas.

(b) Find the change in entropy of one mole of carbon dioxide, when its absolute temperature increased by 3 times if the process of heating is:

(i) Isochoric

(ii) Isobaric

II. (a) Define and find expressions for Thermo-emf, Peltier co-efficient and Thomson co-efficient.

(b) The entropy of v= 3.0 moles of an ideal gas increases, by    S = 23 JK-1 due to isothermal expansion. How many times should the volume of the gas be increased or decreased?

III. (a) How does Heat pump differ from Refrigerator? Prove that the amount of mechanical energy required to extract a given amount of heat from a cold body increases with decrease in temperature of the body, for a given temperature of the sink.

(b) A heat engine employing a Carnot cycle with an efficiency of n=20% is used as a refrigerating machine, the thermal reservoir being the same. Find its refrigerating efficiency &.

UNIT-II

IV. (a) Derive Clapeyron's equation from Maxwell's relations and explain the change of ice to water on the basis of it.

(b) Making use of Maxwell's thermo-dynamical relation prove that cooling is produced when the substance which contracts on heating is compressed.

V. (a) What are thermodynamic potentials? What is their significance? Deduce the relation

(b) Derive thermodynamically an expression for Joule-Thomson Co-efficient. Show that for a perfect gas Joule-Thomson effect vanishes.

VI. (a) Find an expression for the change in temperature of wire when stretched adiabatically.

(b) Prove that the specific heat at constant volume for a Vander Waal gas is equal to the specific heat at constant volume for a perfect gas.

UNIT-III

(Compulsory)

VII. Attempt any six parts :

(a) How will the entropy change during free expansion of a gas?

(b) Find the change in the energy of a system if 300 J of work is done on it, while 65 calories of heat flows out of it.

(c) Write the Clausius-Claperyron's equation. What is its significance?

(d) Correct representation of Ist law of thermodynamics is

(e) How does free electron gas differ from an ordinary gas?

(f) Why Seebeck effect is not an independent effect?

(g) Two stars radiate maximum energy at wavelength 3.0x10-5 cm and 5.0x10-7 m respectively. What is the ratio of their temperatures?