Dielektrikke

Dielektrikke, commonly referred to as dielectrics, are insulating materials that do not conduct electric current under normal conditions but respond to electric fields by becoming polarized. This polarization reduces the internal electric field and enables the storage of electrical energy in devices such as capacitors. In linear, isotropic dielectrics, the electric displacement D, the electric field E, and the polarization P are related by D = ε0 E + P = ε ε0 E, where ε0 is the vacuum permittivity and ε = εr is the relative permittivity or dielectric constant.

Dielectric polarization arises from several mechanisms, including electronic polarization (displacement of electron clouds), ionic polarization (shifts of ions), and orientational polarization (alignment of permanent dipoles). Dielectric strength—the maximum field a material can withstand before breakdown—varies widely among materials, from modest values in polymers to very high values in specialized ceramics and insulators. Energy losses in dielectrics are described by dielectric loss, often expressed through a complex permittivity ε* = ε' − jε'' and a loss tangent tan δ = ε''/ε'. These losses depend on frequency and temperature.

Materials used as dielectrics range from natural substances like air and glass to synthetic polymers (polyethylene, polypropylene, PTFE) and ceramic ferroelectrics (e.g., barium titanate). Dielectrics are essential for energy storage and insulation in a wide range of technologies, including capacitors, power cables, transformers, and electronic sensors. They are classified by properties such as permittivity, dielectric strength, loss, frequency response, and crystalline structure, and by their behavior under electric, thermal, and mechanical stresses.