Dielectric materials for electric light sources

In metal conductors (and carbon conductors), the outermost electrons of their atoms are less attracted by the nucleus and can easily leave the nucleus, becoming free electrons and moving irregularly between atoms. The conductivity of metal conductors and carbon conductors depends on these free electrons. The more free electrons there are, the stronger the conductivity.

In air, water, kerosene, glass, ceramics, mica, plastics, rubber and other materials, the outermost electrons of their atoms are difficult to escape from the gravitational range of the nucleus. Therefore, they have very few free electrons and poor conductivity. These objects are called insulators, also called dielectrics.

In the production of electric light sources, glass materials are the most widely used dielectric materials, followed by ceramics, mica, plastics, asbestos, etc.