Ohm's Law - current within parallel plate capacitor imbedded in a large volume

[PhysicsUnderg]

Homework Statement

A parallel plate capacitor with plates of area A and separation d is imbedded in a large volume filled with a material with electric conductivity σ. Determine the total current I if the two capacitor plates are maintained at a potential difference V_o. Explain how such a device could be used to measure the salinity of salt water.

Homework Equations

E=V/d, V=IR

The Attempt at a Solution

I am probably wrong, but I just calculated E=V/d=IR/d, and then solved for I which gives I=Ed/R=EdσA/L... ?? Any help is appreciated. For some reason, I have a really hard time going about electromagnetism problems and I am not sure even how to think of them.

 

[jbsteele]

To measure the salinity of salt water, the capacitor plates can be used to measure the conductivity of the water. By knowing the area and separation of the plates, the potential difference between them can be calculated and then the current can be determined using Ohm's law. The more salt present in the water, the higher the conductivity and the higher the current that is measured.