P. 4692. A straight coil of length \(\displaystyle L=20\) cm, of cross-section of \(\displaystyle A=12~\rm cm^2\) and of number of turns \(\displaystyle N=400\) can rotate in the horizontal plane along a vertical axle through its centre. The coil is in uniform horizontal magnetic field of induction \(\displaystyle B=0.05\) T. Initially the coil is perpendicular to the magnetic induction, and there are two unstretched springs attached to both of its ends, as shown in the figure. The other ends of the springs are also fixed and initially the springs are perpendicular to the coil. The spring constant of the springs is \(\displaystyle D=24\) N/m, and their length is \(\displaystyle \ell_0=20\) cm.
After the switch is turned on, there will be current in the coil. What is the current in the coil if the coil will be in equilibrium after turning an angle of \(\displaystyle \alpha=60^\circ\)?
Deadline expired on 12 January 2015.