Problem 3.206

\(3.206 .\) A coil of radius \(r=25 \mathrm{~cm}\) wound of a thin copper wire of length \(l=500 \mathrm{~m}\) rotates with an angular velocity \(\omega=300\) rad/s about its axis. The coil is connected to a ballistic galvanometer by means of sliding contacts. The total resistance of the circuit is equal to \(R=21 \Omega\). Find the specific charge of current carriers in copper if a sudden stoppage of the coil makes a charge \(q=10^{\circ} \mathrm{nC}\) flow through the galvanometer.