Changes

<math>\Delta\varphi(\vec r)=-\frac{\varrho(\vec r)}{\varepsilon_0}</math>

Once the potential is computed, the electric fields can easily be computed via:

<math> \mathbf{E(\vec r)} = - \nabla \varphi(\vec r)</math>

EM.Ferma can also compute magnetic fields from simple line sources via the Biot-Savart Law: