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This java applet is a simulation that demonstrates magnetostatics and electromagnetic waves in two dimensions.

When the applet starts up you will see a white circle (called the "source") emitting red and green circular waves. The color indicates the electric field; green areas are positive (towards you) and the red areas are negative (away from you). (In this applet, the electric field is always perpendicular to the plane of the screen; that means there are no free charges, and all currents have to be perpendicular to the screen as well. It also means the electrostatic potential is zero everywhere.)

In addition to the red and green color, you will see arrows which indicate the direction of the magnetic field (which is always in the plane of the screen).

Also, sources and conductors may show a blue or yellow color, indicating current. Yellow means that current is flowing towards you and blue means it is flowing away from you.

Conductors, dielectrics, and other media will show up as gray. There aren't enough colors or shades of gray to make the different kinds of media look different. Use the Show Material Type menu option to tell them apart.

These are electromagnetic waves, so in real life they would be moving at the speed of light.

This is the TM version of the applet. There is also a TE version.

The Setup popup can be used to view some interesting pre-defined experiments. Once an experiment is selected, you may modify it all you want. The choices are:

The Source popup controls the wave sources (oscillating currents). It has the following settings:

The Mouse popup controls what happens when the mouse is clicked. The following settings are possible:

The Show popup determines which fields or other quantities to display, and how to display them.

The Clear Fields button magically clears out any fields but does not remove any currents, sources, or materials. The Clear All button clears out everything.

The Stopped checkbox stops the applet, in case you want to take a closer look at something, or if you want to work on something with the mouse without worrying about it changing out from under you.

The Simulation Speed slider controls how far the waves move between frames. If you slide this to the left, the applet will go faster but the motion will be choppier.

The Resolution slider allows you to speed up or slow down the applet by adjusting the resolution; a higher resolution is slower but looks better.

The Brightness slider controls the brightness, just like on a TV set. This can be used to view faint waves more easily.

Click here to go to the applet.