Problem 3.272

A permanent magnet has the shape of a sufficiently thin disc magnetized along its axis. The radius of the disc is \(R=1.0 \mathrm{~cm} .\) Evaluate the magnitude of a molecular current \(I^{\prime}\) flowing along the rim of the disc if the magnetic induction at the point on the axis of the disc, lying at a distance \(x=10 \mathrm{~cm}\) from its centre, is equal to \(B=30 \mu \mathrm{T}\)