4_8.asv

层结构的电力线分布图

clear all;
a=1;
b=2*a;
E0=1;
eps0=8.854187817620392E-12;
eps=4*eps0;
phi=[0:0.01:1]*2*pi;
r=[1:0.001:3];
n_phi=length(phi);
n_r=length(r);
K=b^2*(eps+eps0)^2-a^2*(eps-eps0)^2;
Er=zeros(n_phi, n_r) ;%行数，列数
Ephi=zeros(n_phi,n_r);
for j=1:n_r
    for i=1:n_phi
        x
        if r(j)<a
            Er(i,j)=4*eps*eps0*b^2/K*E0*cos(phi(i));
            Ephi(i,j)=-4*eps*eps0*b^2/K*E0*sin(phi(i));
        elseif r(j)>b
            Er(i,j)=(1-(b^2-a^2)*(eps0^2-eps^2)/K*b^2/r(j)^2)*E0*cos(phi(i));
            Ephi(i,j)=-(1+(b^2-a^2)*(eps0^2-eps^2)/K*(b/r(j))^2)*E0*sin(phi(i));
        else 
            Er(i,j)=   2*eps0*b^2/K*((eps+eps0)-(eps-eps0)*a^2/r(j)^2)*E0*cos(phi(i));
            Ephi(i,j)=-2*eps0*b^2/K*((eps+eps0)+(eps-eps0)*a^2/r(j)^2)*E0*sin(phi(i));
        end
    end
end



plot3(phi,r,Er)