Three charges ... Again! - E and V graphs

Description: This physlet lets you adjust 3 point charges (change the sign, the magnitude, and the location), and see the Electric field (E) graphs, or the Electric Potential (V) graphs. If you only want one charge, set the other ones to zero charge! [Note : there is more information further down on this page!]

Set the starting values :



X position





Which variable to plot in the lower graph?
     Plot E   Plot V   Plot Both

To rescale the electric field graph.
    Xmin=     Xmax=
    Ymin=     Ymax=
  * If you manually change values ...


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 charged objects 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. [Note, in this physlet, the test charge is allowed to pass through the rings (since they are hollow), and thus the motion seems very reasonable, physically.]

Hey, my charge disappeared! Part IIBecause of the way the physlet animates the motion of the test charge .. there is some unphysical behavior here .. the test charge appears able to pass through one of the charges - not possible! If a positive test charge is approaching another positive .. at some point, it would be turned away (in real life) .. or if it is approaching a negative charge, it would be pulled in completely. Since the animation works in "frames" .. it calculates a new velocity, and position ... and based on the speed, that might "jump" the test charge past the fixed charge ... that shouldn't happen in real life! If you want to play with test charges that can move freely along the axis .. look at the charged rings physlet.

Credits : Created by Scott Schneider.

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