Magnetic reluctance
= Magnetic reluctance
{title2=$\mathcal R=\int dl/(\mu_0\mu_rA)$}
{wiki}
The <magnetic reluctance> of a linear section of <magnetic circuit> is the ratio of the winding's integrated <magnetic field intensity> to the <magnetic flux>, with units $\mathrm{A\,Wb^{-1}}$. For uniform length $\ell$, cross-sectional <area> $A$, and relative <magnetic permeability> $\mu_r$, $\mathcal R=\ell/(\mu_0\mu_rA)$. Series sections carrying the same <magnetic flux> have additive <magnetic reluctances>, and $NI=\Phi\sum_i\mathcal R_i$.