Vacuum permeability
= Vacuum permeability
{title2=$\mu_0$}
Vacuum permeability is the <magnetic permeability> appearing in the vacuum <Maxwell equations>. In <SI>, it relates vacuum magnetic field strength to <magnetic flux density> through $\mathbf B=\mu_0\mathbf H$ and obeys $\mu_0\varepsilon_0c^2=1$, where $c$ is the <speed of light> and $\varepsilon_0$ the <vacuum permittivity>.