# Homework Help: I need help

1. Mar 22, 2010

### zahraa

I need help PLZ :(

1. The problem statement, all variables and given/known data
A small insulating spherical shell with inner radius a=1cm and outer radius b=2cm is concentric with a larger insulating soherical shell with inner radius c=4cm and outer radius d=6cm . the inner shell has a nonuniform charge distribution =.005 r C/m^3 , and the outer shell has a uniform charge distribution and a total charge of 5 nC .

2. Relevant equations

my question is what will the electric field be at boint at a distance r=5cm from the common center of both spheres

3. The attempt at a solution

q/(4*pi*E0*(b-a)^2) ??

2. Mar 22, 2010

### zahraa

Re: I need help PLZ :(

pllllllllllllz :(

3. Mar 22, 2010

### Kabbotta

Re: I need help PLZ :(

Hey zahraa,

Just determine the volume enclosed by the portion of the outer shell that is contained within your Gaussian surface. Use that to get the portion of the charge enclosed by that part of the shell.

Then for the nonuniform part of the enclosed charge form an integral over the volume to get the portion of the charge enclosed by the inner shell's volume.

Add those enclosed charge values and use Gauss' Law for the Gaussian shell with radius 5cm.

$$EA = \frac{q_{in}}{\epsilon_{0}}$$