A straight rod of mass $\mathrm{m}$ and length $\mathrm{L}$ is suspended from the two identical springs as shown in figure. The spring is stretched a distance $\mathrm{y}_{0}$ due to the weight of the wire. The circuit has total resistance $\mathrm{R}$. when the magnetic field perpendicular to the plane of paper is switched on, springs are observed to extend further by the same distance $y_{0}$ the magnetic strength is