(Solved): Question 4: Calculate the magnetic field of a disc of radius \( R \) with uniform surface charge den ...

Question 4: Calculate the magnetic field of a disc of radius \( R \) with uniform surface charge density \( \sigma \), rotating about its axis at an angular velocity \( \omega \). How about the magnetic field of a solid sphere of radius \( R \) with a uniform volume charge density \( \rho \), spinning at angular frequency \( \omega \) ? Please give your answers for the inner and outer region of the sphere.