IEVref: 121-11-14 ID: Language: en Status: Standard Term: magnetic constant Synonym1: permeability of vacuum [Preferred] Synonym2: Synonym3: Symbol: μ0 Definition: scalar constant linking the electromagnetic quantities and the mechanical quantities, obtained from the relation $\frac{F}{l}=\frac{{\mu }_{0}}{2\pi }\text{\hspace{0.17em}}\cdot \text{\hspace{0.17em}}\frac{|{I}_{1}{I}_{2}|}{d}$ where F/l is the magnitude of the lineic force between two straight parallel conductors of infinite length and negligible circular cross-section, placed at a distance d apart in vacuum and carrying electric currents I1 and I2 Note 1 to entry: In a vacuum, the product of the magnetic constant and the magnetic field strength H is equal to the magnetic flux density B: B = μ0H Note 2 to entry: The magnetic constant is related to the electric constant ε0 and to the speed of light in vacuum c0 by the relation μ0ε0c02 = 1. Note 3 to entry: The value of the magnetic constant is equal to 1,256 637 062 12(19) × 10−6 N A−2. Publication date: 2021-01 Source: Replaces: 121-11-14:1998-08 Internal notes: CO remarks: TC/SC remarks: VT remarks: Domain1: Domain2: Domain3: Domain4: Domain5: