### Presenting .. your Electric Field!

 Note : when the lines are red - the applet is calculating the electric field .. wait a second for it to finish. Introduction : This applet illustrates the Electric field for different charge configurations. The default view is the Electric field lines. Try the configurations below: Also, the charges are "dragable"! You can click down on a charge and move it around (it will have to recalculate the electric field lines though - be patient!). Now, we could now look at the Electric Field using a "vector field." The vector field picks discrete points, in a grid, calculates the electric field magnitude and direction, and then puts a little vector down with the strength of the field (as color) as well as the direction. It is much faster (since we only pick some points, instead of following a whole line). Click the radio button below for the vectors .. then you can go select the configurations above. (Note: if you select one configuration, and switch between lines and vectors - notice that the vectors and lines should "line up" where they both exist in the image.] E-field lines     E-field vectors Things to try :      With the vectors - move one charge on top of another!      With unequal unlike charges and vectors - can you find the E=0 point?

Extra feature .. animation! If you put the test charge somewhere in the system, you can click the RESTART/PLAY button to "release" the test charge from rest - it will be acted upon by the other charges and move toward or away, depending on the net force on the test charge (if it hits one of the charges, there will be a "collision" and the animation will stop). Now, using that RESTART/PLAY button will start the test charge from rest! If you want to pause the motion, and not move the charge, then continue that same motion, use the RESUME FROM PAUSE button. [See, I found that if you move the charge to a new place, you want to start it from rest .. otherwise the applet would keep the old velocity from the pause - which caused weird, non-physical behavior. So, if you move the charge - use the RESTART/PLAY button ... if you just pause the motion, and then want to continue that motion without you adjusting the test charge .. use the RESUME FROM PAUSE.]

Hey, my charge disappeared! If you test charge flies off the screen to either side, or if it collides with one of the fixed charges - use the RESET button to restore the initial configuration.