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## Homework Statement

We have solid ball of radius r

_{b}and charge density [tex]\rho[/tex].

I need to find the magnitude of electric field E(r) at a distance r < r

_{b}from the center of the ball and express my answer in terms of [tex]\rho[/tex], r, r

_{b}, and [tex]\epsilon[/tex]

_{0}.

## Homework Equations

Gauss's Law

[tex]\int[/tex] EA = Q/[tex]\epsilon[/tex]

_{0}

## The Attempt at a Solution

E*(4*[tex]\pi[/tex]*r

_{b}

^{2}) = 4*[tex]\pi[/tex]*r

^{3}*[tex]\rho[/tex]/(3*[tex]\epsilon[/tex]

_{0})

E(r)= (r

^{3}*[tex]\rho[/tex])/(3*r

_{b}

^{2}*[tex]\epsilon[/tex]

_{0})

But the website I check my answers with tells me it's wrong. Can someone help me to understand, please? The hint it gave me was that my answer should not depend on r

_{b}. Why wouldn't it?