Permeability constant

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The permeability constant, magnetic constant or permeability of free space (μ₀) is the permeability of vacuum (or of free space). It is a mathematical factor relating mechanical and electromagnetic units of measurement (so that the force of electromagnetic interactions are measured in the same units as mechanical force).

It is defined as the ratio of magnetic field density to magnetic field strength in vacuum:

It is related to the electrical permittivity of vacuum (also electric constant) by

where:

μ₀ - magnetic constant

c - speed of light

In SI units, the value is exactly expressed by:

μ₀ = 4π×10⁻⁷ N/A² = 4π×10⁻⁷ H/m

[edit] See Also

• Electric constant, also known as the permittivity of vacuum.

[edit] References

• NIST - CODATA 2002 recommended values - magnetic constant. Retrieved on August 31, 2005.