When handling stationary electric currents in conductive media you must consider the stationary equation of continuity. In a stationary coordinate system, the point form of Ohm’s law states that:

where σ is the electrical conductivity (SI unit: S/m), and Je is an externally generated current density (SI unit: A/m2). The static form of the equation of continuity then states:

In planar 2D the Electric Currents interface assumes that the model has a symmetry where the electric potential varies only in the x and y directions and is constant in the z direction. This implies that the electric field, E, is tangential to the xy-plane. The Electric Currents interface then solves the following equation, where d is the thickness in the z direction:

In 2D axisymmetry, the Electric Currents interface considers the situation where the fields and geometry are axially symmetric. In this case, the electric potential is constant in the  direction, which implies that the electric field is tangential to the rz-plane.