# Need help with gauss law and charged ring AP Physics FRQ

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1. Mar 17, 2013

### lodovico

1. The problem statement, all variables and given/known data
1.
2.

2. Relevant equations
∫E.dA = Qenc/$\epsilon$$_{o}$
$\lambda$=Q/L
$\rho$=Q/V
V= q/4πε$_{o}$r

3. The attempt at a solution

these types of problems i suck at, i dont know how to do these at all independently, and is there any difference in question 2 if there is an insulator or not? is that irrelevant?

I have the scoring guidelines with the answers but they dont really teach anything

2. Mar 17, 2013

### rude man

This is a simple exercise in applying Gauss's theorem.

To answer your question, yes it matters if the inside sphere is an insulator or a conductor. It matters for r < R.