  The transport and distribution of charged particles are crucial in the study
of many physical and biological problems. In this paper, we employ an Energy
Variational Approach to derive the coupled Poisson-Nernst-Planck-Navier-Stokes
system. All physics is included in the choices of corresponding energy law and
kinematic transport of particles. The variational derivations give the coupled
force balance equations in a unique and deterministic fashion. We also discuss
the situations with different types of boundary conditions. Finally, we show
that the Onsager's relation holds for the electrokinetics, near the initial
time of a step function applied field.
