2D Electric potential/field in parallel plates capacitor

Solving numerically the 2D Laplace equation for parallel plates capacitor.

Solving numerically the 2D Laplace Equation for parallel plates capacitor
using finite differences method, convergence is attained using the norm's
criterion with tolerance=6.00, Number of iteration N=611.

-Laplace : d²U(x,y)/dx²+d²U(x,y)/dy²=0
-boundaries : U(x=0,y)=0, U(x=L,0)=0, U(x,y=0)=0, U(x,y=L)=0.
Derivation of the numerical solution is detailed in the file"Laplace2D_E_U.pdf".

Parameters :
- Dimensions : square box of length L=200 mm .
- Voltage : two plates : (1) at 220 volts and (2) at -220 volts.
- distance : between plates d=80 mm .
- density : rho=0 vacuum between plates.

Outputs :
- Electric potential U(x,y).
- Electric field E(x,y).

Screen Shot :
left : result of the distribution of the electric potential .
right : Image from the "Manufactures & Exporters of Scientific
& laboratory Equipments".
http://www.jsexports.com/capacitor-parallel-plates-280.html