Charge: 1 q
Maximum arrow size:
Show field:
Scan along axis:
Show grid points

This web app displays the magnetic fields associated with various current distributions. Hold down the control key and drag on the display to change your viewpoint, and hold down the option key while dragging on the display to zoom in or out. The red, green, and blue lines are the x, y, and z axes, respectively. The green arrow shows the direction that the charge distribution is moving or rotating.

For each configuration, the app displays the field vector at each point predefined rectangular grid of points. To see the grid locations, click on the "Show grid points" checkbox. Please note that field vectors may not appear at certain locations if the vector is either too large or too small to display well. Changing the value of the "Charge magnitude" slider will make the arrows either smaller or larger. Doing this can expose field vectors at locations where they are too small to see at the default charge magnitude. You can flip the sign of the charge distribution by using the "+/–" button. (Note that positive charges are red, negative charges are blue.) Decreasing the value of the "Maximum Arrow Size" slider will hide field arrows that are larger than a certain limit: this can help one better see the smaller arrows in a region. In certain cases, arrows may also be suppressed if showing them would be misleading. If an arrow is suppressed at a location for any reason, its grid point (when shown) is displayed at a larger size to indicate this.

To make studying the field easier, you may also choose to display the field vectors evaluated only on a certain plane using the "Show field" menu. If you select a certain plane, then you can used the "Scan along axis" slider to move the center of that plane up or down the axis perpendicular to that plane.

[Javascript coding by Tom Moore, and Jake Hauser, and Nik Papastavrou, using the Glowscript library (]