dielectriciteitsconstant

The dielectric constant, known in Dutch as dielectriciteitsconstant, is a material property that describes how a material responds to an electric field and how it stores electrical energy. In mechanics of electricity, it is typically represented by the relative permittivity, denoted ε_r.

The relative permittivity ε_r is defined as ε_r = ε/ε0, where ε is the absolute permittivity of the material and ε0 is the vacuum permittivity (approximately 8.854×10^-12 F/m). The dielectric constant is therefore a dimensionless quantity. The absolute permittivity of a material is ε = ε_r ε0.

In a capacitor, the dielectric constant directly influences capacitance. For a parallel-plate capacitor with plate area A and separation d, the capacitance is C = ε_r ε0 A/d. Thus, materials with higher ε_r allow larger capacitance in a given geometry. The value also affects the electric field distribution and breakdown characteristics of insulating materials.

The dielectric constant generally depends on frequency. At low frequencies, multiple polarization mechanisms (electronic, ionic, orientation, interfacial) can contribute, giving a higher ε_r. At higher frequencies, some mechanisms cannot respond quickly, reducing ε_r. The material's response is often described by complex permittivity ε* = ε' − jε'', where ε' is the real part (stored energy) and ε'' relates to dielectric loss.

Common values vary widely. Air has ε_r close to 1, water is around 80 at room temperature, and many polymers range from 2 to 4. Ferroelectric materials can exhibit very high ε_r at low frequencies.

Dielectric constants are essential in capacitor design, insulator performance, and high-frequency electronics, where they influence impedance, signal propagation, and energy storage.