A wide, very long, insulating belt has a uniform positive charge per unit area $\sigma$ on its outer surface. Rollers at each end starts rotating from rest with variable angular acceleration, $\alpha {\text{=at}}^{\text{2}}\text{+bt+c.}$ Where a, b, c are constants and t is time elapsed from the starting of the motion. There is no slipping between the belt and the rollers. The radii of the rollers is r and the length of the belt is L. r<<L. The magnitudes of magnetic field at P (a point in between the belts) and Q (a point outside and close to the belt) as shown int the diagram at a time t respectively are neglect the edge effect ie., the length of the belt which is contact with pulley.