Charge strength: 1 nC





Welcome to the Electric Field Explorer. This simulator is not intended as a replacement to the HTML PhET "Charges and Fields", but as a supplement. Several features work in a smilar fashion to the PhET, 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.

The point of a grid is to help with precise measurement. To that end, 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 because it is more important to place them on a field line rather than at a known point in space.

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. However, the numerical integration is done with lower accuracy while sliding, otherwise the program lags horribly. When students release the mouse, the fields they see will change, sometimes dramatically. If they ask about this, you can explain what is going on.

The plates in Capacitor mode are not metal plates, but insulating sheets of charge. As a result, the plates are 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. (The computational overhead of setting up a mesh and using finite elements to solve Laplace's equation whenever the plates are moved is too large, at least for now.) Be aware that for computational puposes, the plates are square. You are looking at the field in a cross-sectional plane that bisects the capacitor (and also the single charged plate).

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

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.