51. A rod of length L with uniform charge density per unit length is in the xy-plane and rotating about z-axis passing through one of its edge with an angular velocity as shown in the figure below. (F.6.2) refer to the unit vectors at Q. A is tghe vector potential at a distance d from the origin O along z-axis for d < < L and J is the current density due to the motion of the rod. Which one of the following statements is correct? (a) J Z UP along F; A along 2; OC (b) J along A along A 1 x d (c) J along P; A along 2; | (d) J along ; A along A OC