BPHCT-135 · December 2025 · English
IGNOU BPHCT-135 December 2025 Previous Year Question Paper
THERMAL PHYSICS AND STATISTICAL MECHANICS
Structured previous year question paper for BPHCT-135, December 2025 session.
Max marks: 50 · Questions: 5
Verified: 24 Aug 2026
BACHELOR OF SCIENCE (GENERAL)
(BSCG)
Term-End Examination
December, 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) Write Zeroth Law of Thermodynamics and state its physical significance.
(b) Draw Andrew’s curves for CO2.
(c) Write the expressions for 0,v,,,, and v, for a Maxwellian gas.
(d) Write the expressions for enthalpy and Helmholtz energy.
(e) Write the expression for C,—C, for an ideal gas and a van der Waals’ gas.
(f) State Joule-Thomson effect. Write the expression for Joule-Thomson coefficient.
(g) Plot spectral energy density of a black body with wavelength at three different temperatures (T, > Tz > Ts).
(h) Write the Boltzmann relation between entropy and probability. What is its significance ?
Q2.Answer any two parts: 2x5=10
(a) Obtain an expression for survival equation for distribution of free paths.
(b) Define coefficient of viscosity. Discuss the effect of temperature and pressure on viscosity.
(c) Show that sedimentation is an example of Brownian motion. Discuss its utility in daily life.
Q3.Answer any two parts : 2x5=10
(a) Derive equation of state for a thermodynamic system assuming volume as a function of pressure and temperature. Imposing the condition dV=0 and dT+0, prove that the thermodynamic variables are connected through a relation : OP )p\ OT Jy OV Jp
(b) 1 g of water and steam at normal atmosphbic pressure occupy 1 cm® and 1671 cm’? volume, respectively. Calculate the change in internal energy for vaporisation of water at 100°C. Take latent heat of steam as 540 cal and J=4.2J cal.
(c) Obtain Laplace’s formula for speed of sound.
Q4.When two phases of a substance coexist in equilibrium at constant temperature and pressure, their specific Gibbs’ free energies are equal. Using this fact, obtain Clausius- Clapeyron equation. 10 Draw the indicator diagram of a Carnot cycle. Obtain the expression for the work done during one cycle of Carnot engine and hence deduce its efficiency. 2+4+4
Q5.Starting from the expression for thermodynamic probability given by : i N,Mg,-D! obtain the expression for Bose-Einstein distribution function.