
\sect{Gas in electric field}

%Baruch's  A18

An ideal gas of classical charged particles with mass
$m$ is confined between two capacitor plates of area $A$,
separated by distance $L$. The capacitors produce a force $f$
perpendicular to the plates which pushes the particles to the
lower plate. The particles can be absorbed on either plate, with
an absorption potential $-\epsilon <0$; on each plate the
particles can move freely. The system is in equilibrium at
temperature $T$. The average density of the non-adsorbed
particles, i.e. those between the plates, is $n_0$.
\begin{itemize}
\item[(a)] Evaluate the density $n(x,y,z)$, choosing $z$ perpendicular
to the plates.
\item[(b)] Evaluate the densities on the lower and
upper plates.
\item[(c)]  Evaluate the forces acting on the top
and bottom plates. Is there a net force on the capacitor?\\
\end{itemize}

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