Hello Hwang In saying that the gap between the coated plates does not matter (when the conducting solution flows through it) we are making an assumption that the solution is acting as a perfect conductor. However, if you compare the conductivities of the two, the conductivity of the solution is around 5 S/m while the conductivity of a perfect conductor is of the order of 10^10 S/m. Also, this solution has a dielectric constant of 78. Would it not contribute to any capacitance. The structure is: M | I | sea water | I | M where M - metal, I - insulation layer. An AC voltage of low frequency is applied accross the metals. Is it possible for you to give me an equivalent circuit model for this system ? Any help will be appreciated[/img]