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The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the electric permittivity of a vacuum. A dielectric is an insulating material, and the dielectric constant of an insulator measures the ability of the insulator to store electric energy in an electrical field.
PCB warning label on a power transformer known to contain PCBs. Polychlorinated biphenyls (PCBs) are organochlorine compounds with the formula C 12 H 10−x Cl x; they were once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectric and coolant fluids for electrical equipment. [2]
Another common term encountered for both absolute and relative permittivity is the dielectric constant which has been deprecated in physics and engineering [3] as well as in chemistry. [ 4 ] By definition, a perfect vacuum has a relative permittivity of exactly 1 whereas at standard temperature and pressure , air has a relative permittivity of ...
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In standard units, the Bjerrum length is given by = , where is the elementary charge, is the relative dielectric constant of the medium and is the vacuum permittivity. For water at room temperature ( T ≈ 293 K {\displaystyle T\approx 293{\text{ K}}} ), ε r ≈ 80 {\displaystyle \varepsilon _{r}\approx 80} , so that λ B ≈ 0.71 nm ...
In chemistry, ion association is a chemical reaction whereby ions of opposite electric charge come together in solution to form a distinct chemical entity. [1] [2] Ion associates are classified, according to the number of ions that associate with each other, as ion pairs, ion triplets, etc. Ion pairs are also classified according to the nature of the interaction as contact, solvent-shared or ...
The energy U stored in an electrostatic field distribution is: = | | Knowing the magnitude of the electric field of an ion in a medium of dielectric constant ε r is | | = and the volume element can be expressed as =, the energy can be written as: = = Thus, the energy of solvation of the ion from gas phase (ε r =1) to a medium of dielectric constant ε r is: = (=) = ()
Polarizability is responsible for a material's dielectric constant and, at high (optical) frequencies, its refractive index. The polarizability of an atom or molecule is defined as the ratio of its induced dipole moment to the local electric field; in a crystalline solid, one considers the dipole moment per unit cell . [ 1 ]