New trends in physics teaching, v.4; The ... - unesdoc - Unesco

Introductory statistical physics
dp = -nmg dh
m being the mass of one molecule. The rest follows using kinetic theory.
Feynman then presents this result, not as a special case but as an instance of a general result
n = constant exp(-E/kT)
in which exp(-E/kT) is the Boltzmann factor with mgh generalized to any appropriate potential
energy difference.
Figure 1 shows how Feynman’s strategy works, After an introduction on random walks to
introduce statistical distributions, the exponential atmosphere argument is used to go straight to
applications of the Boltzmann factor, of which he gives several varied examples. But nowhere
Exponential
atmosphere
Boltzmann
factor
ll
Reversible and
i rrevers i b le
processes
Chance
State, distribution
Einstein solid; Boltzmann factor;
Mixing W,,,
Q‘/Q =N/n
c a I cu lat io n by
permutation unit change
quantum shuffling
Isothermal
expansion
AlnQ=Nln2
A S =NRTA 1nV
Entropy: use of
numerical values
I
Uses of Boltzmann:
vapour pressure
Uses of entropy:
equilibrium
meltlng, evaporation
engines. cycles
statistical
Figure 1. Feynman’s introductory method.
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