# Electric Flux through the semisphere

1. Sep 4, 2006

### YoungILoveYou

Hello, if we have an electric field E parallel to X axis and a semisphere with axis parallel to X axis, which is the electric flux through the semisphere?

2. Sep 4, 2006

### Andrew Mason

The flux is:

$$\phi = \int E\cdot dA$$

Since flux is a dot product of the field and area, the flux through the semisphere is the same as the flux through the projection of the semisphere onto the yz plane (which is perpendicular to x axis).

AM

3. Sep 5, 2006

### YoungILoveYou

Another thing.
If there is a sphere centered at the origin, with radius R, the Flux is zero?
I think that is similar to cube example!

http://img153.imageshack.us/my.php?image=cubeqq7.jpg

What do you think?

Bye

4. Sep 5, 2006

### Tomsk

Yes, if there's no charge inside it, which there wouldn't be with that field, I think. If there is a charge inside the sphere, the flux is Q/epsilon0.