Substances that are not good at conducting current are called insulators, and insulators are also called dielectrics.

They have extremely high resistivity. Definition of insulator: Objects that do not conduct electricity easily are called

insulators. There are no absolute boundaries between insulators and conductors.

Features

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. The macroscopic current formed by the

movement is considered to be a non-conductive substance.

Conductivity

The conductivity of an insulator is determined by the behavior of electrons in the substance. The behavior of

electrons in a crystal depends on the energy band structure. A substance with a completely empty conduction

band and a full valence band is an insulator. The energy difference between the bottom of the conduction band

and the top of the valence band (band When the energy gap is large, it does not conduct electricity under the

usual electric field. For substances with small energy gaps, although they are insulators when the temperature

is low, when the temperature increases, the valence band electrons are excited to the conduction band, and they

will also conduct electricity. In addition, when the electrons or holes on the impurity level in the band gap are

excited to the conduction band or valence band, it will also conduct electricity.

Electric field strength

Solid insulators are divided into two types: crystalline and amorphous. The actual insulator is not completely

non-conductive. Under the action of a 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.