I've been trying out different ways to plot field lines and I think I've found a good one. I tried using tracking in Gogebra but it was too messy. I wanted the test charge to move cleany in the direction of the field. The problem is that once moving the charge will continue moving in that direction rather than following the field line, which gives its direction of acceleration not motion. The solution was too use Algodoo with loads of air resistance. This prevents the particles from overshooting the field line. Looks neat anyway.