Please help! How to find the potential difference of a spherical shell

stunner5000pt

I can frankly say i'm totally confused on how to solve this problem. Here it is:

A think spherical shell of charge Q and uniform volume charge density p is bounded by radii r1 and r1 where r2>r1. WIth V=0 at infinity find the electric potential V as a function of the distance from the centre of the distribution considering the regions:

a) r > r2 Ans. V = kQ/r because the spherical distribution will act like a point charge when any point is taken outside the shell, by Gauss Law

b) r2 > r > r1 Ans. completely confused here...Using the concept in the first part a) i would think from the iner radii point of view

Vsmall = kQ/r

but since it is enclosed in a bigger radii i have no idea how to proceed

c) r < r1 if the previous confused me then this one is so above my head it's orbiting the earth

d) do these results agree at r = r2 and r = r1 ... Well if i could answer b and c then i might be able to answer this one

Claude Bile

c) should be easy, if the Electric field is zero inside the shell, what does this say about the potential?

b) is a little trickier. How does the Electric field behave inside the shell? Does it go up as r^2? Use Gauss' Law if you must.

d) The answers should agree, if not, then a mistake has been made.

Claude.