BPHCT-135 · June 2025 · English
IGNOU BPHCT-135 June 2025 Previous Year Question Paper
THERMAL PHYSICS AND STATISTICAL MECHANICS
Structured previous year question paper for BPHCT-135, June 2025 session.
Max marks: 50 · Questions: 5
Verified: 24 Aug 2026
BACHELOR OF SCIENCE
(GENERAL) (BSCG)
Term-End Examination
June, 2025
BPHCT-135 : THERMAL PHYSICS AND
STATISTICAL MECHANICS
Time : 2 Hours Maximum Marks : 50
Note :
(i) All questions are compulsory.
However, internal choices are given.
(ii) The marks for each question are
indicated against it.
(iii) Symbols have their usual meanings.
(iv) You can use a calculator.
Q1.Attempt any five parts : 5x2=10
(a) State third law of thermodynamics and give its mathematical expression.
(b) State van der Waals’ assumptions for real gases.
(c) Plot Maxwellian distribution function as a function of molecular speeds at three different temperatures.
(d) Einstein discovered that Brownian displacement was independent of mass of suspended particles. Who verified this finding and how ?
(e) List thermodynamic variables required for specifying a dielectric substance in an electric field.
(f) Write Kelvin-Planck statement of 2nd law of thermodynamics.
(g) Plot M-B, F-D and B-E distribution functions vs. £—". Assume that each system is at the same temperature and has same number of particles.
(h) Draw V-T and P-T diagrams for isobaric process.
Q2.Answer any two parts: 2x5=10
(a) Write the basic assumptions of kinetic theory of ideal gases.
(b) Calculate v,,,, for helium atoms at 27°C. At what temperature will oxygen molecules have the same value of v,,,, ? Take my, =6.67x10" kg
(c) Calculate the average velocity of a system of particles in random motion.
Q3.Answer any two parts: 2x5=10
(a) State first law of thermodynamics. Show that for an ideal gas, it can be expressed as : 5 8Q = CyaT + pdV and 6Q=CpdT-—pdV
(b) Obtain an expression for volume expansion coefficient for one mole of van der Waals’ gas. 5
(c) Derive equation of state for an adiabatic process and hence obtain the work done during this process.
Q4.Write the four Maxwell’s relations of thermodynamics. Using these relations, obtain the first and second TdS relations. 44343 Starting with the Planck’s radiation law : wan = Othe] eg . 2° Lexp(hc/Akp T)-1 deduce
(i) Rayleigh-Jean’s law,
(ii) Wien’s law, and
(iii) Stefan’ law. 2+2+6
Q5.The thermodynamic probability for a F-D distribution is given by : w=7JJ—2i. _ Ul 8 77! 7! Obtain expression for F-D distribution function. Plot the Fermi function for T = 0 K and T>0K. 8+2 Obtain the partition function for a single particle monoatomic ideal gas. 10 mM ? my, =6.67x10-" fem cif 3Q= CydT + pdV और 3Q = C,dT + pdV ud = omhe (aanena| dh “ 2° Lexp(hc/AkpT)-1 fran, atk
(iii) er a Pras qe TT 24246 WTNH