dielectricum

Dielectricum, in physics and engineering, refers to a dielectric material—an insulating substance that can be polarized by an electric field. When placed in an external field, the material’s molecules or bound charges arrange to oppose the field, enabling the storage of electrical energy and the increase of capacitance in nearby conductors. The key parameter is the permittivity ε of the material, usually expressed as the relative permittivity ε_r = ε/ε_0, which quantifies how strongly the material polarizes in response to the field.

Polarization occurs through several mechanisms: electronic polarization via distortion of electron clouds, ionic polarization from relative motion of ions, and orientational (dipolar) polarization in polar molecules. In polar dielectrics, permanent dipoles align with the field; in nonpolar dielectrics, polarization is mainly induced. The dielectric constant depends on frequency, typically decreasing with increasing frequency, and on temperature and moisture, which can also affect dielectric strength.

Key dielectric properties include the dielectric constant (ε_r), dielectric loss (tan δ), and dielectric strength—the maximum sustainable electric field before breakdown. Dielectrics are selected for high breakdown strength, low loss, chemical stability, and suitable mechanical properties for their role. Common materials range from air and glass to ceramics (such as alumina), mica, and polymers (polyethylene, polypropylene, PTFE, epoxy resins), as well as insulating oils.

Applications include insulating layers in capacitors and cables, substrates for printed circuit boards, transformer insulation, and microwave components where stable permittivity and low loss are required. Dielectric materials are evaluated through capacitance measurements, impedance spectroscopy, and breakdown testing to determine ε_r, tan δ, and dielectric strength across temperatures and frequencies.