Understanding the Equation ε=ΔV/r: Parallel Plates vs. Point Charges

[BlueCardBird]

For the equation ε=ΔV/r, does this work only between 2 parallel plates or would it work for point charges as well?

 

[CWatters]

http://en.wikipedia.org/wiki/Electric_potential#Electric_potential_due_to_a_point_charge

 

[Xidike]

I love Electrostatics <3

 

[Khashishi]

Do you know calculus? Your equation seems to be another way of writing $|E| = \Delta V/\Delta r$, which is only an approximation. The correct value is gotten by taking the limit as Delta goes to 0. Then you get:
$E=-\nabla V$
In the special case of infinite parallel plate, they give the same answer, but for a curved E field you get a more accurate answer for smaller step size.