Problem 3.299

A small coil is introduced between the poles of an electromagnet so that its axis coincides with the magnetic field direction. The cross-sectional area of the coil is equal to \(S=3.0 \mathrm{~mm}^{2}\), the number of turns is \(N=60 .\) When the coil turns through \(180^{\circ}\) about its diameter, a ballistic galvanometer connected to the coil indicates a charge \(q=4.5 \mu \mathrm{C}\) flowing through it. Find the magnetic induction magnitude between the poles provided the total resistance of the electric circuit equals \(R=40 \Omega\).