Problem $6$

A disk of radius $R=1m$ has a surface charge distribution ${}_s=\frac{10}{r_c}(\frac{C}{m^2}).$ The disk is rotated at a constant speed $N=500re\frac{v}{m}in.$ Thus we have electric charges in circular motion, which may be considered to be circular currents. Find B$-$field at a distance of $1\mathrm{.}5$ m from the center of the axis of the disk.