Electrical Resistance

Two electrodes are placed on or embedded in the surface of a test specimen. The following properties are calculated:

Insulation resistance is the ratio of direct voltage applied to the electrodes to the total current between them; dependent upon both volume and surface resistance of the specimen. In materials used to insulate and support components of an electrical network, generally it is desirable to have insulation resistance as high as possible.

Volume resistivity is the ratio of the potential gradient parallel to the current in the material to the current density.

Surface resistivity is the ratio of the potential gradient parallel to the current along its surface to the current per unit width of the surface.

Knowing the volume and surface resistivity of an insulating material makes it possible to design an insulator for a specific application.