exm05522_2.m

matlab程序

%exm05522_2.m
clear;clf;
q=2e-6;k=9e9;a=1.5;b=-1.5;
x=-6:0.6:6;y=x;
[X,Y]=meshgrid(x,y);        %设置网点x,y坐标
rp=sqrt((X-a).^2+(Y-b).^2);
rm=sqrt((X+a).^2+(Y+b).^2);
V=q*k*(1./rp-1./rm);        %计算电势
[Ex,Ey]=gradient(-V);       %计算场强(二元函数的梯度)
AE=sqrt(Ex.^2+Ey.^2);       %场强归一化，使箭头等长
Ex=Ex./AE;
Ey=Ey./AE;
cv=linspace(min(min(V)),max(max(V)),49);    %产生49个电位值
contourf(X,Y,V,cv,'k-')			%用黑实线画填色等位线图
axis('square')					
title('\fontname{隶书}\fontsize{22}偶极子的场'),hold on
quiver(X,Y,Ex,Ey,0.7)	    %第五参数0.7使得场强箭头长短适中
plot(a,b,'wo',a,b,'w+')     %用白线画正电荷位置
plot(-a,-b,'wo',-a,-b,'w-') %用白线画负电荷位置
xlabel('x');ylabel('y'),hold off