  The Jarzynski relation is a recently discovered result relating the average
exponential of the work done under nonequilibrium conditions to an equilibrium
free energy difference. We illustrate this remarkable relation by considering
the expansion and compression of a classical ideal gas particle inside a cavity
with a moving piston in one dimension. Using a simple relationship between the
distributions of the nonequilibrium work done in the two (forward and reverse)
processes, we verify the Jarzynski relation and discuss the practical
realization of the Jarzynski equality for the model.
