Problem 3.332

A small cylindrical magnet \(M\) (Fig. 3.95 ) is placed in the centre of a thin coil of radius \(a\) consisting of \(N\) turns. The coil is connected to a ballistic galvanometer. The active resistance of the whole circuit is equal to \(R\). Find the magnetic moment of the magnet if its removal from the coil results in a charge \(q\) flowing through the galvanometer.