Problem 3.282

An iron core shaped as a tore with mean radius \(R=250 \mathrm{~mm}\) supports a winding with the total number of turns \(N=1000\). The core has a cross-cut of width \(b=1.00 \mathrm{~mm} .\) With a current \(I=\) \(=0.85\) A flowing through the winding, the magnetic induction in the gap is equal to \(B=0.75 \mathrm{~T}\). Assuming the scattering of the magnetic flux at the gap edges to be negligible, find the permeability of iron under these conditions.