# Is the field strength between 2 electrodes dependent in any way on the medium?

I want to apply a high voltage electric field to a particle. Provided the electrodes are at the same distance and relative location from the particle in any case, will it make a difference to the field strength (not asking about the current) experienced by that particle, what the medium is around the particle - whether salt water, plastic, air etc.?

Yes, it will make a difference, usually.

1. A conductive medium will affect the electric field. Salt water is conductive, so it may well distort the field compared to what it'd be if there was vacuum between electrodes.

2. Dielectrics may be add their own induced/retained net charge distribution, either due to pre-polarization or due to the applied external field. Their field superposes on the external field.

Generally speaking, dielectrics don't have to affect the electric field. Vacuum is a well-performing dielectric since it doesn't get electrically polarized, and thus never adds anything to the existing external field.

• So if it were a vacuum, the particle would experience a field strength defined simply by the voltage and separation between the two electrodes and its own characteristic length? While a conductive medium might distort the field so the particle then experiences more or less than this? Commented Apr 3, 2023 at 12:35
• @OliverWalters Exactly. And even a dielectric medium might distort the field, since an external field can polarize the dielectric, thus adding a net charge distribution that will modify the field. Commented Apr 3, 2023 at 12:42