# Homework Help: Conductors and Gauss's law

1. Jan 31, 2004

### eku_girl83

Here is the problems that's giving me trouble:
Positive charge Q is distributed uniformly over each of two spherical volumes of radius R. One sphere of charge is centered at the origin and the other at x=2R. Find the magnitude and direction of the net electric field due to these two distributions of charge at the following points on the x-axis.
a) x=0
b) x=R/2
c) x=3R

Do I use the equation E=1/(4*pi*epsilon) (Q/R^3)??
If so, can someone give me a hint on how to apply it to this problem?

2. Jan 31, 2004

### chroot

Staff Emeritus
You need to use Gauss' Law. Can you begin by explaining to me what Gauss' Law says?

- Warren

3. Jan 31, 2004

### eku_girl83

Gauss's law states that the total electric flux through a closed surface is eqaul to the total electric charge inside the surface divided by Epsilon_0.
EA=Q/Epsilon_0
E=Q/(Epsilon_0*A) in the case of a sphere A=4*pi*R^2
Correct?

4. Jan 31, 2004

### chroot

Staff Emeritus
Yes, that's correct. You should also know that electric fields can be "superimposed." If you find the field due to one sphere, and the field due to the other, you can just add them together to get the total field.

To find the field at each the given points, use Gauss' law twice: once for each of the spheres of charge. Add the results together.

Can you take it from here, or do you need more guidance?

- Warren