A disk with radius R is uniformly charged with charge density o,the disk is rotating about the axis through its center with angular velocity o,Find the magnetic field along the axis of the disk,and the magnetic moment of the disk solution ① dB Hr'-dl 2(x2+r2)32 dB d=”dg 2n dg=o·2πrdn dl wo rdrx P x  R o A disk with radius R is uniformly charged with charge density , the disk is rotating about the axis through its center with angular velocity ，Find the magnetic field along the axis of the disk, and the magnetic moment of the disk solution 2 2 3 2 2 2(x r ) r dI dB o    dI dq   2  dq  2 rdr dI  rdr dr r R dB