  The formulation of the First and Second Principles of thermodynamics for a
particle in contact with a heat bath and submitted to an external force is
analyzed, by means of the Boltzmann-Lorentz kinetic equation. The possible
definitions of the thermodynamic quantities are discussed in the light of the H
theorem verified by the distribution of the particle. The work fluctuation
relations formulated by Bochkov and Kuzovlev, and by Jarzynski, respectively,
are derived from the kinetic equation. In addition, particle simulations using
both the direct simulation Monte Carlo method and Molecular Dynamics, are used
to investigate the practical accuracy of the results. Work distributions are
also measured, and they turn out to be rather complex. On the other hand, they
seem to depend very little, if any, on the interaction potential between the
intruder and the bath.
