Dielectric materials (insulators)

Dielectrics are materials without free charge carriers: ceramics, glass, plastics, air, etc. Dielectrics can be classified by resistivity, and breakdown voltage per cm thickness.

The higher the voltage of a transmission line, the longer the insulators.

When a voltage is established across a sheet of dielectric it becomes polarized - with positive charge on one side and negative on the other. A class of materials (plastics) retain the polarization after the field is removed. A object with permanent polarization is called an electret.

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