A dielectric is a material that does not conduct electricity but can support an electric field. These materials are essential in various electrical applications, as they can store electrical energy when placed in an electric field. Common dielectrics include glass, ceramics, and plastic. When a dielectric is subjected to an electric field, it becomes polarized, meaning that its positive and negative charges shift slightly. This polarization allows the dielectric to store energy, which is crucial in devices like capacitors. The effectiveness of a dielectric material is often measured by its dielectric constant, which indicates how well it can store electrical energy compared to a vacuum.