# Homework Help: Gauss' Law: Net Electric Field of Two Spheres

1. Sep 6, 2008

### UWGGEOL

1. The problem statement, all variables and given/known data
Two nonconducting spheres, of r1=3.0cm and r2=2.0cm, are placed of an x-axis. They have surface charge densities of +6.0mC/m2 and +4.0 mC/m2, respectively, on their outside surfaces. The center of sphere r1 is on the origin and the center of sphere r2 is 10 cm away. What is the net electric field at x=2.0 cm?

2. Relevant equations
E=kq/r2
Area=4pir2

3. The attempt at a solution
I noticed that x=2.0cm falls inside sphere r1 and that the Electric Field inside a sphere due to an outside charge equals 0. I think this is the answer but want to be sure.

2. Sep 6, 2008

### astrosona

I do not think so!!!! because they are non conducting spheres..... so we can not ignore the effect of the second sphere, I guess!!! i will look it up more though...

3. Sep 6, 2008

### Goddar

The field inside a uniformly charged sphere is zero (the field of THIS sphere vanishes), but the field outside a uniformly charged sphere is the same as if all the charge was at its center (we can treat it like a point-charge on most regards)... You should get your answer easily!

4. Sep 6, 2008

### UWGGEOL

Yeah I tried that before you told me and it was pretty easy and good to know the way i thought was right. I got -3.10x10^3 N/C because of the direction of the field