I am in the process of trying to find out the potential of a uniformly magnetised sphere with radius $a$. What I need to work out is the following:
$\int\int\frac{d\vec{S} }{|\vec{r}-\vec{r'}|}$
where I am directing the $z$-axis along $\vec{r}$
and $ d\vec S= (\sin θ \cos ψ \vec{i}+\sin θ \sin ψ \vec j+cos θ \vec k)a^ 2 \sin θdθdψ$, $\vec {r'}=a\sin\theta\cos\psi\vec{i}+a\sin\theta\sin\psi\vec j+a\cos\theta\vec k$
I have gotten as far as working out the modulus to be $\sqrt{a^2+r^2-2ar\cos\theta}=R$
I think I have to convert $d\vec S$ somehow but I am really stuck and need help please.