Hi, I hope this is the appropriate place and format etc. One of the questions I have to answer is this: Use Gauss's law to obtain the field, everywhere, of charge of uniform density roe, occupying the region a<r<b, where r is the distance from the origin. I am completely flummoxed as to what assumptions I can make.. I am assuming that since we are asked to use Gauss that I should use a spherical symmetry.. I also think that where r<a the field should be zero, but can I assume that the charge lies on the inner surface only for this region? And where r>b should I treat the whole dstribution as a point charge? Also, I have started trying to find E inside the a<r<b, using Q= integral(roe dV),and I end up with a term involving b^3-a^3. If anybody could tell me if i'm on the right track of give me any pointers it would be very much appreciated. Many thanks.