expt-4

close all;
clear all;

syms x y ep0

k=10^-9/(36*pi);
E=[x^2 y^2];

rho=ep0*divergence(E,[x,y]);
rho=subs(rho,ep0,k);

v=-2:0.1:2;

[xPlot,yPlot]=meshgrid(v);
Ex=subs(E(1),x,xPlot);
Ey=subs(E(2),y,yPlot);
rhoPlot=double(subs(rho,{x,y},{xPlot,yPlot}));
figure(1)
quiver(xPlot,yPlot,Ex,Ey);
hold on
contour(xPlot,yPlot,rhoPlot)
title('contour plot of charge density over electric field')
xlabel('x');
ylabel('y');