Application of insulators

An insulator is a substance that does not normally conduct electric current. Also known as dielectric. The characteristics of insulators are that the positive and negative charges in the molecules are tightly bound, and there are very few charged particles that can move freely. Their resistivity is very large, about 10 ~ 10 ohm · meters. Therefore, under normal circumstances, the macroscopic current formed by the free charge movement under the action of external electric field can be ignored, and they are considered as non-conductive substances. Insulators can be divided into gaseous (such as hydrogen, oxygen, nitrogen and all gases in the non-ionized state), liquid (such as pure water, oil, paint and organic acids, etc.) and solid (such as glass, ceramics, rubber, paper, quartz, etc.) three categories. Solid insulator is divided into crystal and non - crystal two kinds. The actual insulator is not completely non-conductive. Under the action of strong electric field, the positive and negative charges inside the insulator will break free and become free charges, and the insulation performance will be destroyed. This phenomenon is called dielectric breakdown. The maximum electric field strength that a dielectric material can withstand is called the breakdown field strength. In the insulator, there is bound charge, under the action of external electric field, this charge will make microscopic displacement, resulting in polarization charge, which is the so-called polarization of the dielectric. According to their physical properties, dielectric can be divided into isotropic dielectric and anisotropic dielectric. The polarization mechanism can be divided into two kinds: the non-polar molecule and the polar molecule. Insulators are widely used in engineering as electrical insulation materials, capacitors and special dielectric devices such as piezoelectric crystals.