Problem 3.164

Demonstrate that the law of refraction of direct current lines at the boundary between two conducting media has the form tan \(\alpha_{2} / \tan \alpha_{1}=\sigma_{2} / \sigma_{1}\), where \(\sigma_{1}\) and \(\sigma_{2}\) are the conductivities of the media, \(\alpha_{2}\) and \(\alpha_{1}\) are the angles between the current lines and the normal of the boundary surface.