Today I decided to leave GeoGebra alone for a bit and start to revise my Electricity lesson plans for the new syllabus starting with electric fields. So I wonder if I could model electric fields with GeoGebra? Easily sidetracked I managed a simple version that nicely reinforces the vector nature of field strength. Here is the worksheet Electric fields simulation (GeoGebra).

Also found this magnificent simulation by Nathaniel Cunningham, I've got a long way to go.