Franklin for Mac

From Paul Peters:

Franklin allows the entry of up to 500 point charges in 3 dimensions. The charge data can be saved to disk for later use. Field lines and equipotentials are easily drawn as are 3D equipotential contours. Changes to the charge configuration can be done from a separate window. Franklin is best viewed on a high resolution screen with the window expanded to full size. This program is intended as freeware for science education.