posted by Robert .
Now we also know that the charge on a pair of parallel plates is proportional to the potential difference V, namely
We also know that the capacitance of two parallel plates is given by
where ε0=8.85×10-12 is the permittivity of free space and d is the separation between the plates. Combine these equations and to get the force as a function of the potential. So now if you were to make a graph of force (F) vs. V2/d2, the slope of the graph would be