Problem 3.309

A long straight solenoid of cross-sectional diameter \(d=\) \(=5 \mathrm{~cm}\) and with \(n=20\) turns per one \(\mathrm{cm}\) of its length has a round turn of copper wire of cross-sectional area \(S=1.0 \mathrm{~mm}^{2}\) tightly put on its winding. Find the current flowing in the turn if the current in the solenoid winding is increased with a constant velocity \(\dot{I}\) \(=100 \mathrm{~A} / \mathrm{s} .\) The inductance of the turn is to be neglected.