This very simple example demonstrates the effect of applying periodic boundary condition, which forces the field potential to be the same on opposite sides of the model.

**Problem Type:**

A nonlinear plane-parallel problem of magnetostatics.

**Geometry:**

Two regions, *A* and *B*, have the same shape, volume loading and are surrounded by Dirichlet boundary condition, which does not allow the field to penetrate outside. Region *B* is also subdivided into *B _{1}* and

**Solution:**

This example also demonstrates that the mesh on the periodic boundary is not necessarily the same - please notice that the mesh spacing settings in four corners of the model are all different!

See the *Perio1.pbm* problem in the Examples folder. *Perio1odd.pbm* is almost the same, but for one difference: odd periodic condition is applied, which forces the field potential to be opposite on two sides of the region.