GraphingCalculator 4;
Window 47 9 856 1412;
PaneDivider 402;
SignificantDigits 14;
FontSizes 14;
BackgroundType 0;
BackgroundColor 255 255 255;
StackPanes 1;
SliderControlValue 18;
UseAntialiasing 0;
2D.Scale 0.1 0.1 5 5;
2D.BottomLeft -1.41875 -2.15;
2D.Axes 0;
2D.GraphPaper 0;
Text "Point charges – fields and potentials
";
Color 3;
Expr a=-0.675+1.13125*i;
Color 4;
Expr b=1.859375-(0.015625*i);
Color 5;
Expr c=-1.265625+1.25*i;
Text "d regulates the singularity";
Expr d=0.01;
Color 6;
MathPaneSlider 32;
Expr Q_1=slider([-5,5,40]);
Color 7;
MathPaneSlider 8;
Expr Q_2=slider([-5,5,40]);
Color 8;
MathPaneSlider 20;
Expr Q_3=slider([-5,5,40]);
Color 2;
Expr function(V,x,y)=Q_1/sqrt([x-Re([a])]^2+[y-Im([a])]^2+d)+Q_2/sqrt([x-Re([b])]^2+[y-Im([b])]^2+d)+Q_3/sqrt([x-Re([c])]^2+[y-Im([c])]^2+d);
Color 17;
XYType 2;
Expr z=function(V,x,y);
Expr E_1=-function(oppartial(x),function(V,x,y)),E_2=-function(oppartial(y),function(V,x,y));
Text "Field vectors:";
Color 2;
Grain 0.6666666666666666;
Expr vector(d*x,d*y)=vector(E_1,E_2);
Text "Field lines (hold opt to see ""total derivative"" in Math menu):";
Color 17;
Grain 0.8;
Expr function(optotal(t),vector(x,y))=vector(E_1,E_2);
Text "

Author: David A. Craig <<http://web.lemoyne.edu/~craigda/>";