The following picture is a representative 3Dimensional view of the electric potential (Volts) for a separated+ and - charge (an electric dipole). The potential is represented by height (vertical) at positions in the xy plane. The charges are located in the xy plane. The positive at x=+1 y=0 and the negative at x=-1, y=0.
Ideally the peaks should go to + and - infinity respectively, but I did not calculate
the potential exactly at the charge (calculations are at points on a 150x150 grid....thats
22,500 points so be impressed). This has the effect of smoothing over the
"true" infinite peak at the charges. Everywhere else the electric
potential is fairly well represented.
The steepness of the electric potential hill at some x,y point is proportional to the
electric field at that point. The direction in which the hill is steepest indicates
the direction of the electric field at that point. A positive charge released at
rest somewhere on this plot would start moving downhill. As it picks up speed
the positive charge may not move in the most downhill direction (it may pick up momentum
and cut accross E field lines). You have seen this type of effect: Consider
water (or yourself) going down a waterslide. When you start you are at the bottom of
the rounded trough. If placed, at rest, in the slide at any point along the slide
you will start moving down hill in the direction that is steepest. As you pick up
speed you may slip up a wall on a curve. The field line is like a line down the
slide at the bottom of the trough. Water does not follow that line as it picks up
speed. It slips all over the place. However, water placed at rest anywhere in
the slide will START OUT following that line!
