Each source contributes a field E = kq/r² pointing away from
positive charges and toward negative ones. Arrows show the vector
sum of every source at each grid point in 3D — length and colour
both track magnitude.
By superposition, the net field at any point P is the vector sum
over every source i: E(P) = Σ k·qi / ri²
· r̂i, where ri is the distance from
source i to P and r̂i is the unit vector pointing from
that source toward P (Coulomb's law).
- + charge / − charge — add a positive or negative point source (up to 6).
- Reset — restore the default two-charge dipole.
- Field density — sets the resolution of the sampled grid, i.e. how many arrows are drawn.
- Charge magnitude — scales |q| for every source at once, stretching or shrinking arrow lengths and the probe reading.
- Probe |E| — the field magnitude computed live at a fixed point away from the charges, via Coulomb superposition.
This same superposition principle underlies real engineering
problems such as capacitor design and electrostatic precipitators,
where the combined field of many charged surfaces must be shaped
precisely.