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 φ direction, which implies that the electric field is tangential to the rz-plane.