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University : Mohan Lal Sukhadia University
Degree : B.Sc
Subject : Thermodynamics & Statistical Physics
Year : II
Document Type : Question Paper
Website : mlsu.ac.in

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MLSU Thermodynamics Question Paper

Second Year Examination of the Three Year Degree Course, 2001
(Faculty of science )
PHYSICS Paper-I (Thermodynamics and Statistical Physics)

Related : Mohan Lal Sukhadia University Electromagnetics B.Sc Question Paper : www.pdfquestion.in/5804.html

Time : 3 Hours
[ Maximum Marks :50]
Attempt any five questions, selecting at least one question from each unit, All questions carry equal marks.

UNIT-I

1. (a) Explain the principle of cooling a system by adiabatic demagnetization. 4
(b) Explain the terms ‘mean free path’, and ‘collision cross section’ for particles in a gas. 2+2

(c) Two particles in a gas move with the same speed making an angle q with each other. Calculate the speed of one of the particle relative to the other? 2
2. (a) Find an expression for the work done by an ideal gas in its adiabatic expansion. 4

(b) How are the root-mean-square, average and most probable speeds of particles in a gas defined? Find out the rms speed of atoms in argon gas at 300K. Atomic weight of argon is 40. 3+3

UNIT-II

3. What is Joule-Thomson coefficient? Derive a general expression for it and, hence,find the Joule-Thomson coefficient for a Van der Waals gas. 2+4+4
4. (a) Derive Maxwell’s second thermodynamic relation. 5
(b) Express the difference in two heat capacities of a system in terms of its other measurable macroscopic parameters. 5

UNIT-III

5. (a) A black-body of volume V is at temperature T. Find out the number of vibrations of the radiation between wavelengths l and l+dl. 6

(b) A furnace is at temperature T. The maximum of the radiation intensity emitted by it occurs at wavelength lm. Temperature of the furnace is raised to 2T. At what wavelength will now the maximum occur, and by what factor will the maximum height increase or decrease? 2+2

6. (a) Find average energy of a Plank oscillator. 6
(b) The operating temperature of a tungstan filament in an incandescent lamp is 2460 K, and its absorptance (or absorptivity) is 0.35. Find the surface area of the filament of a 100-W lamp.

UNIT-IV

7. (a) A system consists of four spin-half particles fixed in space. Tabulate all the possible microstates of the system. 5

(b) A system consisting of N spin-half particles fixed in space is kept in magnetic field B. The probability of a particle with its spin being found parallel to B is p. Find out the probability of macrostate in which the number of spins parallel to B is n. 5

8. Write down the Bose-Einstein distribution function, and derive an expression or the spectral distribution of energy density of blackbody radiation. 2+8

UNIT-V

9. What do you understand by ‘Platinum temperature’? Is is identical with ideal gas temperature? If not, explain how Platinum resistance thermometer is used to measure temperatures, and in what range. 2+2+6

10.(a) Describe a method for measuring critical constants of a gas
(b) How is the Solar Constant determined? 4 Constants Avogargdro Number (NA) = 6.02×1023/ mole Stefan Boltzmann constant (s) 5.67×10-8 W/m2-K4 Boltzmann constant (k) = 1.38×10-23J/K

Syllabus

Paper-I : 2161 Kinetic Theory, Thermodynamics and Statistical
UNIT – I :
Ideal Gas : Kinetic Model, Deduction of Boyle’s law, Review of the kinetic model of an ideal gas, Interpretation of temperature, Brownian motion, Estimate of the Avogadro number, Equipartition of energy, specific heat of monatomic gas, extension to di and triatomic gases, Behaviour at low temperatures, Adiabatic expansion of an ideal gas. Application to atmospheric physics (derivation of barometric equation)

Real Gas : Van der Waals model; equation of state, nature of Van der Waals forces, comparison with experimental P-V curves. The critical constants, gas and vapour. Joule-Thomson expansion of an Ideal gas and Van der Waals gas; Constancy of U+pV, Joule coefficients, Estimates of J-T cooling, adiabatic expansion of an ideal gas.

Liquification of gases : Joule Expansion, Joule-Thomson and adiabatic cooling, Boyle temperature and inversion temperature, principles of regenerative cooling and cascade cooling, Liquification of hydrogen and helium, meaning of efficiency.

UNIT – II :
Transport phenomena in gases : Molecular collisions, mean free path and collisioncross-sections, Estimates of molecular diameter and mean free path, Experimental determination of mean free path. Transport of mass, momentum and energy and interrelationship, dependence on temperature and pressure.