# Electricity and magnetism (Gauss' law)

• Silentwhale

## Homework Statement

Given two things spherical shells radii r1 and r2 with r2 > r1.
The inner she'll is charged uniformly with a total charge Q1, while the outer shell with Q2.

A) use gauss law to computer the electric field everywhere
B) Use any method to calculate the potential everywhere.

## The Attempt at a Solution

I will be attempting this problem soon just wanted to post the question so I wouldn't waste time it is for my midterm practice. Thank you. I will post my trial solution when I am done trying this problem. Thank you

OK so here is my attempt to the problem:

A) EA = (Qin/ε) (volume ratio)

E (
4(pi)r1^2) = (Q1/ ε) ((4/3 pi r1^3)/(4/3 pi r2^3))

E (
4 pi r1^2) = Q1 r1^3 / ε r2^2

E=
Q1 r1^3 / ε r2^3 4pi r1^2

E
= Q1 r1 / 4pi ε r2^3

E
= KQ1 r1 / r2^3 final answer for a

B)
v= kQ1/r1 + kQ2/r2

V
= (9 x 10^9 Nm^2/ c^2)(Q1/r1 + Q2/r2) answer part b

A) EA = (Qin/ε) (volume ratio)

Volume ratio? You have a typo in your post, but I believe what you intended to type was “thin shell”. Your “volume ratio” suggests you are considering these to be uniform charge densities. Also, even if that were the case, the electric field will have different functional forms over different domains of radius. You have to find a separate answer for each domain.

I do not understand where A) came from. What is this volume ratio? As pointed out in post #3, you are asked to find the electric field everywhere, so first take the case where you want the electric field somewhere inside the inner sphere. Write down the law of physics that you are going to use to solve the problem and aply that law.