Fields at the ends of a parallel plates

[Pranav Jha]

Why do the field lines bulge out at the ends of plates with finite lengths? I understand why the field is uniform between infinitely long plates but cannot extend the concept to plates with fixed length:(

I know they have to bulge but why not bulge inwards rather than outwards?

 

[tiny-tim]

Hi Pranav Jha!

Basically, it's because they prefer to go perpendicular to the surface …

at the end, that's outward! ​

 

[rcgldr]

The field lines bulge out because the ends of the plates are similar to a dipole.

http://en.wikipedia.org/wiki/Dipole

 

[marcusl]

Another explanation comes from realizing that the configuration must have minimal total energy. Curving the lines inwards increases the field strength in between the plates, leading to higher stored energy. (Energy is proportional to the square of the density of flux lines.) Energy is minimized when the lines spread out into space with low density.