Consider a spherical shell of inner and outer radius a and b, respectively, and conducting a uniform current density J = @J, (where Jo is al constant), which is always tangent to circles of constant latitude, as shown below. Find the vector potential A and the B field at the center of the sphere (i.e., at z=0).

Consider a spherical shell of inner and outer radius a and b, respectively, and conducting a uniform current density J = @J, (where Jo is al constant), which is always tangent to circles of constant latitude, as shown below. Find the vector potential A and the B field at the center of the sphere (i.e., at z=0).