Electric fields between point charges

[schiasso]

I am struggling to grasp the concept of the electric field between two opposite charges. I know that the field is strongest closest to the charge and gets weaker further away from the charge. I also know that the electric field lines go from positive to negative and that they are perpendicular to the equipotential lines.

My question is: Is the electric field on the center line (shortest distance) between two opposite charges constant? If not, how can it be constant everywhere in a parallel plate capacitor?

 

[Repainted]

Nope. Its only constant between two (infinitely large) parallel charged plates because you're summing the electric field due to all point charges on the plate. The many charges spread out on the plates all contribute to the electric field at some point between the plates.

Doing the summation via integration yields the formula for the E-field strength, and if the distance between the plates is much, much smaller than the size of the plates, the E-field is approximately uniform.