A straight rod of mass \( m \) and length \( L \) is suspended from the identical springs as sho...

A straight rod of mass \( m \) and length \( L \) is suspended from the identical springs as shown in figure. The spring is stretched a distance \( x_{0} \) due to the weight of the wire.
\( P \)
W
The circuit has total resistance \( R \). When the magnetic field perpendicular to the plane of paper is switched on, springs are observed to extend further by the same distance. The magnetic field strength is
(a) \( \frac{2 m g R}{L E} \)
(b) \( \frac{m g R}{L E} \)
(c) \( \frac{m g R}{2 L E} \)
(d) \( \frac{m g R}{E} \)