Re: why should for a cap. AREA>>>DISTANCE between
Most of the capacitance theory depends on the assumption of 2 infinite planes. However in real world, we cannot have that. If the area is big enough compared to the distance between the plates, then we can use the assumption that we are dealing with 2 infinite planes. This will be true for the center of the plates, with the electric field going vertically from one plate to the other.
As you move out towards the edges, the assumption isn't true anymore. The electric field will begin to bend and the on the edge, the field actually curves out, making the 'fringe' like field.