2D Electric potential/field in 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