A dielectric is an electrical insulator i.e., a nonconducting material, that can be polarised by an applied electric field which slightly displaces the positive and negative charges of each molecule. A dielectric can sustain a high electric field up to a certain limit. An ideal dielectric has no free charges.
Important commercial dielectrics are of two types, polar and nonpolar.
Examples : Polar dielectrics : Silicones, halogenated hydrocarbons.
Nonpolar dielectrics :
(1) Solid : Ceramics, glasses, plastics (polyethylene, polystyrene, etc.) mica, paper.
(2) Liquid : Mineral oils.
