5" substrate clamped between two surface with orings providing a seal for the electrolyte. Does the e-field vary with localized thickness (dist from substrate to plate)?
Have a look at the following theories: Debye-Hückel, Gouy-Chapman. The ion cloud distribution in a spherical field and at the electrode interface can be reasonably well described. The ions will concentrate at the charged electrode, therefore the field distribution will not be uniform: most of the potential drop will occur at the electrodes. The thicness of the transition layer is described by the ionic strength of the electrolyte. If the layer thickness is higher that this ciritical thickness the filed within the bulk electrolyte will not change too much. You can find the proper equations in any bacis bokk on electrochemistry.
Gyorgy, I should have noted that the substrate is a dielectric, so that I am using the two thin volumes of electrolyte as capacitive plates.
I think this is an interesting question. I am not sure if I understand the geometry exactly, but I think answer will depend strongly on the type of electrolyte. Even though Gyorgy was considering a metal electrode in solution, the theories he mentions are probably a good place to start. From first principles, I think you can consider your structure as a capacitor. The fluid having positive and negative ions or some concentration. If you assume metal_electrode/ fluid/dielectric/fluid/metal_electrode You can then assume a 1 D problem and use Poisson's equation to solve it.. As long as there is no heating or, chemical reactions, or other funny stuff going on, it should become an electrostatic problem. When the potential is applied, you should see the movement of charge that will screen out the total internal fields. If the ion concentration is high, this would occur over a short distance, if the fluid is more insulating the length would be longer. If charge is trapped in or on the surface of the dielectric the lengths would change some. I think if you search for Debye length and electrolyte you may be able to find some numbers. For strong electrolytes, I think the distance can be very short, probably sub micron. Using very pure water, the distances would be significantly longer. However I guess at some point you would need to consider [OH] concentration, or electrolysis.
Sorry, I misunderstood the question. If you put the electrolyte between two polarized dielectric sheets, you will still have surface charges on the dielectric side, only this time it will not be free charge but bound charge. Unfortunately I am not good enough in physics to perform the necessary calculation. Another influencin factor may be the surface adsorption of ions onto the dielectric surface (zeta potential). I hope you will fiond experts to answer your question.
My electrolyte is Li-Cl (nearly saturated aqueous solution), the two liquid capacitor "plates" are bounded by an oring of 4"ID. Dielectric substrate is 0.7mm thick.
Dear James,
The electrolyte can be considered a conducting medium with high ionic conductivity. The electrolyte has an electric conductivity sigma.
So, it has a resistance R= L/sigma A, Since there is a dielectric between the two electrolytic electrodes will drop only a very small voltage on them compared to the those dropped on the electrolyte. This is only the case in charging and discharging phase while a current passing in the capacitor. In case of electrostatic the voltage drop on the electrolyte will be zero and all the voltage will be dropped on insulator. As the thickness of the electrolyte increases its resistance increases.
Best wishes
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