Post Graduate Govt. College for Girls, Sector -11, Chandigarh
Model Test Paper II
B.Sc. II (Non-Medical and Computer Science)
PHYSICS Paper A
Statistical Physics and Thermodynamics
Time Allowed : 3hrs Max. Marks:45
Note: Attempt five questions in all, selecting one question from Unit. Last unit is compulsory.
Note: (i) Attempt five questions in all. Selecting one from each of the four units and
Unit five is compulsory for all.
(ii) Non-programmable calculator are allowed.
(iii) All question carry equal marks.
(iv) Logarithmic tables could be asked.
UNIT - I
Q1. (a) Prove that for a dynamic system the fraction of total time spent in a particular.
Macrostate is proportional to Thermodynamics probability that state. 4
(b) 5 distinguishable particles are to be arranged in 3 compartments of a box. .
(i) Calculate total no. of particles that can go in any compartment.
(ii) Also calculate the probability of Macrostates. (2, 1, 2) 4
(c) Distinguish between Microstates and Macrostates of a system. 2
Q2. (a) Discuss the distribution of n distinguishable particles in K compartments which
are further sub-divided into g cells of equal priori probability. 7
(b) Calculate the percentage Error made in using Stirling’s Formula logen!=n logen-n,
when n=7. 3
UNIT – II
Q3. Derive Maxwell-Boltzmann Law for molecular speeds distribution for Idea Gas.
Show that average molecular speed is given by
Q4. (a) Derive Wein’s Displacement Law and Stefan’s Law from Planck’s Law of
Black body radiation. 7
(b) Calculate the number of ways of arranging 8 Fermions in 12-Phase space cells 3
UNIT – III
Q5. (a) What are Reversible and Irreversible processes? Show that process of Expansion
of Gas is irreversible in nature. 3
(b) 60 gm of water is heated from 00c to 1000C. Find the change in Entropy of water.
Specific heat of water is 1 cal/gm/0 K. 4
(c) Explain how concept of Entropy leads to IInd Law of Thermodynamics. 3
Q6. (a) What is S-T diagram? Using it, derive an expression for efficiency of Carnot’s
heat engine. 5
(b) A Carnot heat engine absorbs. 1000 J of heat from a reservoir at 1270C and rejects
600J of heat during each cycle. Calculate: (i) Efficiency of engine, (ii) Temp. of Sink, (iii) Amount of useful work done during each cycle. 5 UNIT – IV
Q7. (a) Prove Clapeyron’s equation of Latent heat and explain of pressure on B.P. of
liquid. 5
(b) Heat is produced by Adiabatic compression a substance. Explain in by using
Maxwell relations. 5
Q8. (a) Derive an expression for cooling produced by adiabatic demagnetization of
paramagnetic salt. 6
(b) Calculate fall in temperature produced by adiabatic throttling process of a gm mole
of oxygen when pressure is required by 70 atmospheres. The initial temp. is 170C.
Give for oxygen Cp=7.03 cal/mol-K.
A=1.32
B=3.12x10-2Litre/mole
R=8.3x107ergs/K-mole 4
UNIT – V
Attempt any five:
Q9. (a) Give statistical definition of Entropy. 2
(b) Distinguish between Accessible and Inaccessible Macrostates. 2
(c) What is probability of drawing two kings in succession from a pack of cards? 2
(d) What is the minimum size of phase space cell in classical and Quantum
Mechanics?2
(e) What constraints are obeyed by a photon gas at a given temp.? 2
(f) Heat must flow from higher temp. to lower. Explain why? 2
(g) Why does a rubber string heat up on stretching? 2
(h) How internal energy of ideal gas differ from real gas? 2