When the applet starts up you will see the electric field of a single positive charge. The charge can be dragged around the screen with the mouse.
Go through the items in the Setup popup (located in the upper right corner) to view some interesting. pre-defined experiments.
If you have a fast computer, you may want to set the Accuracy popup to "High Accuracy" to get better results.
Huge thanks to Bob Hanson and his team for converting this applet to javascript.