# Dielectrics in series, electric field strength

I am trying to apply a strong electric field to a porous material by applying a strong voltage across two conductive parallel plates that are sandwiching the material. Goal is to align dipoles in the material. I can't achieve high enough field strength due to dielectric breakdown of air in the material's pores, so I am experimenting with coating the material in oil. This does allow a stronger electric field to be applied, but will my material still see this strong electric field or will the presence of the dielectric fluid work against the electric field's strength?

Another way to ask this question might be - can a parallel plate capacitor with dielectrics in series be treated as individual parallel plate capacitors in series, where my material still sees the applied electric field rather than the effective electric field once the polarization field of the dielectric is subtracted out?

I've been working through equations and happy to share quantitative reasoning so far as well unless someone has a quick answer to this.

Thank you!

• Can you work under vacuum instead? Getting the oil out will be a problem I'd think. Nov 6, 2018 at 16:04

will my material still see this strong electric field or will the presence of the dielectric fluid work against the electric field's strength?

If the voltage, applied to the capacitor, stays the same, adding oil, will cause this voltage to be divided between the original material and the two layers of oil presumably formed between the material and the plates, which will weaken the field in the material.

Another way to ask this question might be - can a parallel plate capacitor with dielectrics in series be treated as individual parallel plate capacitors in series

Yes. You'll still have reduced voltage share across your material and, therefore, reduce electric field.

• Thank you for the reply. The oil does not really form its own layer, it ideally just fills up the pores in the material that were previously filled with air. Under this assumption, can my material experience the full applied voltage? Nov 6, 2018 at 3:12
• @user1262799 Sure. Whatever voltage you charge the capacitor to will be applied to the dielectric and, given the same voltage, the field will be the same as well. The fact that the pores are filled with oil may slightly increase the capacitance though. So, for the same voltage, the capacitor will take a little greater charge, but you still can charge the capacitor to whatever voltage you need or whatever voltage it can withstand.
– V.F.
Nov 6, 2018 at 4:20
• So much appreciate your input. Based on your replies, my assumption will be that the voltage across oil regions and voltage across material regions will be the same, but the addition of the oil will only work against the electric field's strength (increase capacitance) in regions occupied by the oil, and will not have an effect on the electric field's strength across the material. This would imply an nonuniform charge distribution across the plates. Anyway thanks! Nov 6, 2018 at 22:11