(Solved): A Plexiglas disk of radius \( R \) is charged with a uniform surface charge density \( \rho_{,} \). ...

A Plexiglas disk of radius \( R \) is charged with a uniform surface charge density \( \rho_{,} \). The disk is rotated at a constant speed of \( N \mathrm{rev} / \mathrm{min} \). Thus we have electric charges in circular motion, which may be considered to be circular currents. Determine the magnetic field intensity at the center of the loop. \[ \begin{array}{l} \mathrm{N}=200 \mathrm{rev} / \mathrm{min} \\ \mathrm{R}=30 \mathrm{~cm} \\ \rho_{s}=20 \mathrm{mC} / \mathrm{m}^{2} \end{array} \]