Insulator in some external conditions, such as heating, under the influence of high pressure will be “breakdown”, and into the insulator
The conductor. Not before the breakdown, non-conductive insulator is not absolute objects. If the voltage is applied across the insulating material, the material will be weak current.
Insulation is usually only trace amounts of free electrons, before participating in the breakdown has not been charged conductive particles mainly by the thermal dissociation of movement out of the intrinsic impurity ions and particles. Reflected in the electrical properties of insulator conductivity, polarization, such as loss and breakdown process.
Is an insulator connector can prevent heat (thermal insulators) or electric charge (electrical insulators) the flow of material. The relative electrical insulator and semiconductor conductor material is, they can smooth the flow of charge (Note: Strictly speaking, the semiconductor is an insulator, because at low temperatures, he would stop the flow of electric charge, unless the other in the semiconductor doping atoms, these atoms can be released to carry the excess charge current). Electrical insulators with dielectric term has the same meaning, but the two terms were used in different fields.
A full sense of the thermal insulator, the second law of thermodynamics could not exist. However, some materials (such as silicon dioxide) is very close to the true electric insulator, resulting in flash memory technology. A larger class of materials, such as rubber and many plastics, wiring for homes and offices for both the “perfect”, there is no security in terms of risk, and high efficiency.
In the absence of a better synthesis of the invention (physical or chemical reaction) of material before, inherent in the nature of the substances, mica and asbestos can be as good thermal and electrical insulator.