Ejs Open Source Forces between point charges Model  java applet by Anne Cox, Francisco Esquembre, Wolfgang Christian and now slightly edited by lookang.
taken from http://www.opensourcephysics.org/items/detail.cfm?ID=9683

Coulomb Force Model
author: Anne Cox, Francisco Esquembre, Wolfgang Christian and lookang (this version)
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_model_CoulombForcewee.jar
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_model_CoulombForcewee01.jar