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The change of name had been made because μ 0 was a defined value, and was not the result of experimental measurement (see below). In the new SI system, the permeability of vacuum no longer has a defined value, but is a measured quantity, with an uncertainty related to that of the (measured) dimensionless fine structure constant.
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
Values shown above are approximate and valid only at the magnetic fields shown. They are given for a zero frequency; in practice, the permeability is generally a function of the frequency. When the frequency is considered, the permeability can be complex , corresponding to the in-phase and out of phase response.
The value of the electron charge became a numerically defined quantity, not measured, making μ 0 a measured quantity. Consequently, ε 0 is not exact. As before, it is defined by the equation ε 0 = 1/( μ 0 c 2 ) , and is thus determined by the value of μ 0 , the magnetic vacuum permeability which in turn is determined by the experimentally ...
The following list includes a decimal expansion and set containing each number, ordered by year of discovery. The column headings may be clicked to sort the table alphabetically, by decimal value, or by set. Explanations of the symbols in the right hand column can be found by clicking on them.
Generally, nonmagnetic materials are said to be para- or diamagnetic because they do not possess permanent magnetization without external magnetic field. Ferromagnetic, ferrimagnetic, or antiferromagnetic materials possess permanent magnetization even without external magnetic field and do not have a well defined zero-field susceptibility.
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
These can be used to convert SI units to their corresponding Heaviside–Lorentz values, as detailed below. For example, SI charge is √ ε 0 L 3 M / T 2 . When one puts ε 0 = 8.854 pF/m , L = 1 cm , M = 1 g , and T = 1 s , this evaluates to 9.409 669 × 10 −11 C , the SI-equivalent of the Heaviside–Lorentz unit of charge.