A dielectric is a material that does not conduct electricity but can support an electric field. These materials are essential in various applications, such as capacitors, where they store electrical energy. Common dielectrics include air, glass, and certain plastics, which can be polarized when exposed to an electric field. When a dielectric is placed in an electric field, it becomes polarized, meaning that its positive and negative charges shift slightly. This polarization reduces the overall electric field within the material, allowing it to store energy more efficiently. The effectiveness of a dielectric is often measured by its dielectric constant, which indicates how well it can store electrical energy compared to a vacuum.