Idea: This question is almost analogous to the spherical insulator with a hole in electrostatics.

7.4 We want to estimate the magnetic dipole moment associated with the motion of an electron as it orbits a proton. We use a “semi-classical” model to do this. Assume that the electron has speed v and orbits a proton (assumed to be very massive) located at the origin. The electron is moving in a right-handed sense with respect to the z-axis in a circle of radius r = 0.53 Å, as shown in the figure below. Note that 1 Å = 10-10 m.