Non-conductors are substances whose electrical conductivity is comparatively low and therefore usually not relevant and is below that of semiconductors. While the term is used in physics for arbitrary materials such as gases and vacuum, in technology it usually only means solids. Other partially synonymous terms are:
- Insulator: In addition to the material property described here, the term insulator also refers to the non-conductive component that is used to fasten electrical components, see insulator.
- Insulating material: If non-conductors are used to insulate electrical conductors, for example in cables, they are called insulating materials.
- Dielectric: If the insulating materials determine the electrical properties of electrical or electronic components (e.g. capacitors or coaxial cables), they are referred to as dielectrics.
- Non-conductors include most non-metals, as well as hydrocarbons and many other organic compounds.
Ideals Non-conductors do not conduct electric current, they have an infinitely high resistance and no free moving charge carriers, which makes their conductivity zero. However, there are no ideal non-conductors (since the perfect vacuum does not exist in nature), only in a few experiments could the properties of the ideal non-conductors be (approximately) achieved. Real non-conductors, on the other hand, always have a weak conductivity and thus a finite resistivity, depending on the temperature. Nevertheless, they can often be treated as ideal non-conductors and their conductivity neglected.
Due to the diversity of non-conductive materials, it is not possible to give a general description of their physical properties other than electrical conductivity. Non-conductors are substances in which the density of free electric charge carriers (electrons and/or ions) is very small, i.e. most charge carriers are tightly bound (electrons to the atoms or ions in the crystal lattice) and thus do not have significant mobility. Very few particles are free to move and form derivative currents.
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The number of freely movable charge carriers increases with increasing temperature and with increasing voltage. Therefore, despite their designation, all non-conductors can be induced to conduct (higher or high) electrical currents with a sufficient amount of energy, e.g. at (very) high temperatures or by applying a sufficiently high voltage. As a result, they are transformed into electrical conductors, but often only for a short time, as solids in particular are often irreversibly destroyed in the process. Thus, apart from the application of a very high voltage, diamond also becomes a conductor in the event of red heat, as does glass, which then melts.
Many substances are non-conductors, one of the most well-known representatives is pure carbon in the modification diamond. However, numerous carbon compounds are also non-conductors, such as amber or various plastics. The latter are used, among other things, for the insulation of cables or for housings. Other non-conductors are ceramic materials, glass or silicones.
Non-ionized, dry gases, such as argon, oxygen or normal dry air, are also non-conductors. In general, the presence of water is responsible for the conductor of many natural substances or mixtures of substances (e.g. wood), which do not conduct the electric current by themselves. This is because distilled or deionized water is considered an insulator, but since some water molecules are always dissociated, ions are available to conduct the electric current and make water a poor insulator. In the case of normal tap water or water in lakes, the dissolved salts (metal and non-metal ions) etc. are added. These increase the conductivity enormously and thus turn water into a conductor.
Salts in the solid state – despite their ionic structure – are mostly non-conductors. The binding forces between the ions are too great for enough ions to move freely enough. However, if salts are melted, this changes: the ions are no longer so tightly bound to their neighboring ions, and so molten salts can transport the electric current well through ion conduction.
