1. Electrical conduction in solid insulators

1.1 Resistance types of solid insulating materials and definitions

The notions of resistance and resistivity, which are generally well-defined for conductors, can be extrapolated to insulating materials, albeit with certain specificities that we will now examine. When a DC voltage is applied to a sample of insulating material, a current flows through it, even though it is not perfect, and this current can be measured. A resistance can therefore be determined.

Under certain conditions, we can then calculate resistivity, which theoretically has the advantage over resistance of not depending on the geometry of the test specimen and the electrodes used. Before continuing, let's recall what happens with a conductor.

A metal wire of cross-section...