dielektri

Dielektri (dielectrics) are insulating materials that do not conduct significant electric current under normal conditions but can support an electric field. When inserted between conductors, they become polarized, creating bound charges that reduce the effective field inside the material and enable the storage of electrostatic energy in capacitors and other devices. Dielektri respond to electric fields through polarization, which can involve shifting bound charges, reorienting molecular dipoles, or displacement of ions.

Key properties include the dielectric constant (relative permittivity, εr), which determines how much a material increases capacitance in a given geometry; dielectric strength, the maximum field the material can withstand before breakdown; and loss tangent (tan δ), a measure of energy dissipation as heat. Dielektri also exhibit dependence on temperature and frequency, influencing performance in real-world circuits. Polarization mechanisms are categorized as electronic, ionic, orientation, and space-charge polarization, each contributing over different field strengths and frequencies.

Classification of dielektri spans polymers (such as polyethylene, polypropylene, and polyimides), ceramic and glassy materials (including barium titanate and alumina), and liquids (oils and refrigerants). Ferroelectric dielectrics, a subset with spontaneous polarization that can be reversed by an external field, are important in nonvolatile memory and high-permittivity applications. Composite dielektri combine insulating matrixes with fillers to tailor properties.

Applications of dielektri include energy storage in capacitors, electrical insulation in cables, transformers, and power equipment, as well as substrates for microelectronics and RF/microwave components. The study of dielektri combines materials science, electromagnetism, and reliability engineering, with standards guiding measurement of permittivity, loss, and breakdown.