QuickField can solve both linear and nonlinear magnetic problems. Magnetic field may be induced by the concentrated or distributed currents, permanent magnets or external magnetic fields.

The magnetic problem is formulated as the Poisson's equation for vector magnetic potential **A**
(**B = curl A**, **B** - magnetic flux density vector). The flux density is
assumed to lie in the plane of model (*xy* or *zr*), while the vector of electric
current density **j** and the vector potential **A** are orthogonal to it. Only *j _{z}*
and

and for axisymmetric case is

where components of magnetic permeability tensor *μ _{x}* and

*Note.* Isotropic (*μ _{x} = μ_{y}* or