1. The problem statement, all variables and given/known data Disk of radius S has uniform charge Q on surface. Roates with angular velocity w = w z(^) about symmerty axis Z. I am asked to find magnetic field (I believe I have that answer though it's messy and maybe wrong) vector potential (of which I have no idea) and the torque on a magnet with magnetic dipole m = m s(^) place in the equitorial plane at a distance s from the center of the disk. 2. Relevant equations ??? 3. The attempt at a solution The first part I have NO idea on. For the second part, torque = mXB m = Iarea = I*pi*S^2 But where does the distance s go? Thank you!