# Motion of a point charge near an electric dipole

1. Sep 15, 2009

### hd90001

I was hoping people might be able to provide some insight into the following fairly basic scenario (not homework/school related). Imagine a positive point charge on the x-axis. Also on the x-axis, to the right, is an electric dipole, with finite spacing, pointed along the x axis, with the positive charge on the right. This is a diagram of the situation:

-----(+)-------------------------(-)--------(+)----------------------------------

Imagine the dipole charges to be fixed. What happens to the velocity and potential energy of the test particle on the left when it is released from rest, at the following positions A-G?

-----(+)A-----------------------B(-)C--D--E(+)F----------------------G----------

Note: Distance A-D is the same as distance D-G.

Does the point charge have enough energy to make it beyond point D (or somewhere between D and E)? Is it reflected and does it oscillate around the negative charge before point D?

Now imagine the same scenario, but the particle has an initial positive velocity to the right. I believe that it needs some initial velocity to get beyond D, but I may be wrong. Imagine that it does have just enough velocity to get up and over point E. What is the velocity and energy at G compared to point A in this case? Will it continue accelerating in the positive x direction forever in this case?

Thanks a lot for your insight!! If anybody has any links to helpful websites/animations/applets, that would be really great too!!