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.