Charge strength: 1 nC

±1 nC charges





Welcome to the Electric Field Explorer. Several features work in a smilar fashion to the HTML PhET "Charges and Fields" and should feel familiar. There are however, some differences, as discussed below. I have adopted the PhET color scheme (red is positive, blue is negative), but only under protest, as everbody knows that electrons are red.

If the grid is on, charges, sensors, and the voltmeter "snap" to the grid (with a 5 pixel resolution) when released. When the grid is off, there is no snapping. The test charges never snap.

In the Dipole and Capacitor modes, the charges can be grabbed and slid closer together or farther apart. If field line drawing is enabled, students can watch the field lines rearrange. To reduce lag, the numerical integration is done with lower accuracy while sliding. When students release the mouse, the fields they see will change, sometimes dramatically. If they ask about this, you can explain.

The plates in Capacitor mode are not metal plates, but insulating sheets of charge, and therefore not equipotential surfaces! Equipotential lines can cross through the plates without violating any physics. This provides a "good enough" model of a real capacitor, especially when the separation is large or small. Be aware that the plates are square. You are looking at the field in a cross-sectional plane that bisects these plates.

Sandbox mode allows for the arbitrary placement of as many charges as the student has patience for. If a charge is placed almost exactly on top of another one, it will "snap" and the result is treated as a single charge that is twice as large. There is no limit to how many charges can be placed in a single stack. In this mode, because of the algorithm, and blah blah, you do not get dynamic field lines as charges are moved.

The auto-drawn equipotentials are shown at 1 V intervals, which the students can verify with the potential meter. The green button on the meter plots an equipotential through the meter location, as in the PhET.

Not only the actual electric field sensors, but also the manually drawn equipotentials and the test charge trajectories are all considered "sensors" and will be erased by the Clear Sensors button and whenever the charge configuration is changed.


Electric Field Explorer v1.00

© Geoff Nunes 2020, 2021

Questions, brickbats, and requests for enhacements can be sent to doc at this website ( Do not expect a rapid response.

This program is an example of what people can be driven to during a pandemic lockdown. There may be bugs.

Change Log


Minor new feature: Arrowheads on Sandbox field lines.