electric field (urgent )

Discussion in 'General Electronics Chat' started by shreyas_bhat, Jul 18, 2005.

  1. shreyas_bhat

    Thread Starter Active Member

    Jul 26, 2004
    I have a parallel-plate capacitor, the plates of which are covered by a thin insulating layer. In the gap between the 2 insulated plates, I have an ionic solution of high conductivity (~5 S/m and dielectric constant = 75). If I apply an AC accross the 2 plates, say 5 V (@ 1KHz), how would the electric field be distributed within this capacitor ?

    I understand that a perfect conductor has charges only on the surface, and a perfect insulator tends to contain most of the electric field. But I'm not sure, how a lossy dielectric (the ionic solution) behaves under the action of an applied electric field. Theoritically, I would assume that most of the electric field would be concentrated within the thin insulation coating layer over the metal plates, and very little electric field in the lossy solution region. Am i correct in assuming that. Please correct, me if I'm wrong.
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    I would be surprised if it were otherwise. The equivalent circuit would be series C-R-C, would it not? I suspect the solution would simply act as a resistor, except where it contacts the insulating plates. At the insulating plates it would act as the plate of a capacitor.

    Of course, I've barked up my share of trees in the past, and this might be another one.
  3. pebe

    AAC Fanatic!

    Oct 11, 2004
    You are barking up the right tree!
    If the insulating film were to be removed from one of the plates, it would behave essentially like an electrolytic capacitor, ie. an anode with its anodic film (dielectric), electrolyte (solution), and cathode (plate with no insulating layer).