The Applet on Page 2 simulates the electric field outside and inside a sphere of uniform charge density. In another mode, the applet simulates the gravitational field outside and inside a sphere of uniform mass density.

The applet will be loaded in its default mode, which is the Gravitational mode. To set it to the Electric mode, click the radio button labeled "Electric".

Detailed information on how to use the applet is available from Applet Help on the applet's Help menu.