EM Field Mapper Applet Documentation

How It Works

The way to calculate the potential energy of a point charge is with Coulomb's law. The problem with that is without an algorithmic approach like in this applet, you must calculate each of the 40000 points on the graph for each sphere and add them. With this applet, you can calculate the electric potential energy of an infinite number of conducting spheres and you are able to see their electromagnetic field, and equipotential lines.


This applet is able to draw the field with the use of electrical potential energy. It uses the formula for electrical potential energy to gather the energy of the individual spheres.

Then it adds them together and displays the sum as a hue on the grid.

How To Use The Applet

  1. Left-Click in the red grid area to add a charged sphere, then the applet will display a box to input the charge of the sphere. Input the desired charge and the sphere will appear where you clicked along with the electromagnetic field around it.
  2. To delete all the spheres on the grid, click the clear spheres button in the input panel.
  3. If you Right-Click in the gridded area, you can add points to mark equipotential points around the sphere.
  4. To delete all the points on the grid, click the clear points button in the input panel.
  5. Select the shading checkbox to show the shading of the electromagnetic field. Deselect the checkbox to hide the shading.