Yes, thanks. The one you mention does look useful. The Charges2000 program
draws higher resolution field lines which are nicer looking and more
suitable for display but requires, on Windows computers "administrative
privileges" which is a problem for me on campus. The PhET program is more
user friendly, flexible and will run on campus without special privileges.
However, the plots are quite coarse.
Don
Dr. Donald Polvani
Adjunct Faculty, Physics
Anne Arundel Community College
Arnold, MD 21012