A dielectric is a type of insulator that becomes polarised when it comes in contact with an electrical field. Such materials are used in many devices such as in capacitors and radios, as well as transmission lines for radiofrequency. Most of the dielectrics are solid in nature but some fluids and gases also exhibit dielectric properties.
Following are a few examples of dielectrics:
- Dry air is an example of gas dielectric
- Mica, ceramic, plastics and glass are solid dielectrics
- Distilled water is a liquid dielectric
As dielectric materials do not conduct electricity, electric charges do not flow normally through them when they come in contact with an electric field. The charges do not actually flow but move slightly from their original position. This results in a dielectric polarization. It causes a positive charge in the material to go toward the electrical field and the negative charges to do the opposite. Thus, an electrical field is created in the material itself and it reduces the overall field of the material. If the molecules of the material are bonded weakly, then they even realign themselves based on their symmetry axes.
Dielectrics are non-conducting materials because they have no free charge carriers. Another major property of dielectric materials is that they do not waste energy in the form of heat while supporting an electrostatic field.