The purpose of electrical insulation

Electrical insulation can be said to be a state of matter rather than a class of materials because there are so many kinds of materials that can be used for insulation. These range from organic fibers, resins, oils, glasses, crystals, minerals and salts through a wide variety of highly dissimulate chemical compounds. All insulating materials are characterized by a scarcity of free elections in their physical structure. Thus, while insulators will conduct current when subjected to electric voltages, the currents are very minute and require relatively high voltages to produce them. It is important that insulators be considered as conductors of very high resistivity. Frequently their resistivity is so high that the current can be neglected for power equipment. Practically the dividing line between conductors and insulators is indefinite as they are separated by another group of materials of intermediate conduction levels.