Electric field plotter
The three colored charges can be dragged to position them, and their charge values can be altered using the sliders.
The slider at right controls whether the charges represent point particles located in the plane, or infinitely long charged rods viewed end-on.
The E-field sensor displays the electric field vector at its location in the plane; drag the green point to sample the field elsewhere.
Drag the purple point to trace more field lines. Drawn lines will be retained until the charges are altered, or the view is adjusted or cleaned up.