Let the velocity of rod be v when it has been displaced by x. Due to motion of rod an emfwill be induced in rod given by e = Bvl. Due to this induced emf, charging of the capacitortakes place as a current flows in the circuit (for very small time). As a result of current, therod experiences a magnetic force given by iBl. From newton’s second law, iBl +kx = ma --- (i) i =
d
dt
(Q) =
d
dt
(C × Bvl) = CBla ... (ii) From (i) and (ii) we get a =