Hi, I just need to ventilate and see your opinions. Charge can be partitioned into groups of particles of one or more elements. If they have more than one element it is a molecule, and its position is represented by for example the center of mass, seeing each particle as carrying both the property of mass and property of charge at the same time. Then, by Taylor expansion of the relative positions of the elements in the groups (the bound charges which seen as a group is a free charge), the H and D fields arise. Also, the center of mass position can be interpreted as the mass concentration in that point, so that the Nernst-Planck equation can be inserted into the expression. This gives an expression for Ohm's law. Do you have anything to add to this?