Problem 3.254

A small coil \(C\) with \(N=200\) turns is mounted on one end of a balance beam and introduced between the poles of an electromagnet as shown in Fig. 3.70. The cross-sectional area of the coil is \(S=1.0 \mathrm{~cm}^{2},\) the length of the arm \(O A\) of the balance beam is \(=30 \mathrm{~cm} .\) When there is no current in the coil the balance is int equilibrium. On passing a current \(I=22 \mathrm{~mA}\) through the coil the equilibrium is restored by putting the additional counterweight of mass \(\Delta m=60 \mathrm{mg}\) on the balance pan. Find the magnetic induction at the spot where the coil is located.