Physics 2 Electric Fields, Circuits, Magnetism

[Adeel Ahmad]

Can someone please help me out with this practice test and provide explanations?

 

[Adeel Ahmad]

So for number 1 a, when r<R, I take +Ze as q and plug it into the equation E = kq/r² and get E = kZe/R². Not sure if that's correct

 

[Adeel Ahmad]

Then for number 1 b when r>R, I assume that E is zero since you set a Gaussian surface that encloses the entire thing so you take the enclosed charge which would be zero since it is +Ze and -Ze which cancels. So when you plug that into solve for E, you would get zero. Please lmk if this is correct.