# Electric field problem

1. Sep 19, 2008

### bodensee9

Hi

Can some one help with this? I don't understand why I keep on getting the problem wrong. A thin hemispherical shell of radius R has uniform surface charge of (sigma). What's E at the base of the electric field?

My reasoning is:

I think that the x and y components of the flux lines cancel and therefore we will only have flux lines coming out in the z direction (both up and down). So, then I can imagine a nice large cylinder with flux lines out of both of the caps. Then I can do 2*E*A = (sigma)*(A)/epsilon. So this will become E*2*pi*R^2 = (sigma)*(3*pi*R^2)/epsilon. So then E is then (sigma)*(3/2)/epsilon?

Thanks.