clear all; clc;

ps=0.002;
e=8.854*10^-12;
r=0:0.00001:0.1;
z1=-0.1;
z2=0.1;
z3=-0.2;
z4=0.2;

E1=sum(ps*z1*(r./(r.^2+z1^2).^(1.5)))/(2*e)
E2=sum(ps*z2*(r./(r.^2+z2^2).^(1.5)))/(2*e) 
E3=sum(ps*z3*(r./(r.^2+z3^2).^(1.5)))/(2*e) 
E4=sum(ps*z4*(r./(r.^2+z4^2).^(1.5)))/(2*e)