dielectriche

Dielectriche refers to materials that behave as dielectrics—insulating substances that become polarized in an electric field. They do not conduct electric current under normal conditions but respond to electric fields by storing and redistributing electric charges. This makes dielectrics essential for controlling electric fields in many devices.

A central property of dielectriche is their permittivity, often expressed as the relative permittivity εr (or dielectric constant). The capacitance of a parallel plate capacitor filled with a dielectric is C = εr ε0 A / d, where ε0 is the vacuum permittivity, A is the plate area, and d is the separation. In general, the electric displacement D relates to the electric field E by D = ε E, with ε = ε0 εr. Polarization P = χe ε0 E describes how bound charges inside the material respond to the field; εr = 1 + χe.

Dielectriche exhibit several polarization mechanisms, including electronic, ionic, orientational, and space-charge polarization, with their dominance depending on frequency and temperature. Dielectric losses, quantified by the loss tangent tan δ, represent energy dissipation as heat and depend on frequency and material purity. The dielectric strength is the maximum electric field the material can withstand before breakdown.

Dielectriche are categorized as gaseous, liquid, or solid. Common solid dielectrics include ceramics, polymers, and mica; gaseous dielectrics include air and sulfur hexafluoride, while oily liquids are used as transformer dielectrics. Applications span capacitors, insulation in cables and equipment, and substrates for high-frequency and microwave circuits. Ferroelectric dielectrics exhibit nonlinear and hysteretic behavior, enabling tunable and memory devices.