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  2. Vacuum permeability - Wikipedia

    en.wikipedia.org/wiki/Vacuum_permeability

    The name "magnetic constant" was briefly used by standards organizations in order to avoid use of the terms "permeability" and "vacuum", which have physical meanings. 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 ...

  3. Permeability (electromagnetism) - Wikipedia

    en.wikipedia.org/wiki/Permeability...

    Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than one (or, equivalently, a positive magnetic susceptibility). The magnetic moment induced by the applied field is linear in the field strength, and it is rather weak. It typically requires a sensitive analytical balance to detect the ...

  4. Vacuum permittivity - Wikipedia

    en.wikipedia.org/wiki/Vacuum_permittivity

    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 ...

  5. List of physical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_physical_constants

    Value [a] [b] Relative standard uncertainty Ref [1] speed of light in vacuum 299 792 458 ... vacuum magnetic permeability: 1.256 637 061 27 (20) ...

  6. Impedance of free space - Wikipedia

    en.wikipedia.org/wiki/Impedance_of_free_space

    Between 1948 and 2019, the SI unit the ampere was defined by choosing the numerical value of μ 0 to be exactly 4 π × 10 −7 H/m. Similarly, since 1983 the SI metre has been defined relative to the second by choosing the value of c 0 to be 299 792 458 m/s. Consequently, until the 2019 revision,

  7. List of electromagnetism equations - Wikipedia

    en.wikipedia.org/wiki/List_of_electromagnetism...

    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 n̂, d is the dipole moment between two point charges, the volume density of these is the polarization density P.

  8. Wave impedance - Wikipedia

    en.wikipedia.org/wiki/Wave_impedance

    In free space the wave impedance of plane waves is: = (where ε 0 is the permittivity constant in free space and μ 0 is the permeability constant in free space). Now, since = = (by definition of the metre),

  9. Biot–Savart law - Wikipedia

    en.wikipedia.org/wiki/Biot–Savart_law

    In physics, specifically electromagnetism, the Biot–Savart law (/ ˈ b iː oʊ s ə ˈ v ɑːr / or / ˈ b j oʊ s ə ˈ v ɑːr /) [1] is an equation describing the magnetic field generated by a constant electric current. It relates the magnetic field to the magnitude, direction, length, and proximity of the electric current.