# Electric field of half a spherical shell

1. Jan 29, 2009

### asi123

1. The problem statement, all variables and given/known data

Hey guys.
I've been trying to solve this question using Gauss law but I can't think of a surface that can contain this thing.
Is there another way to solve this?

Thanks a lot.

2. Relevant equations

3. The attempt at a solution

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2. Jan 30, 2009

### CompuChip

Maybe it helps to draw a picture... suppose that the symmetry axis is the z-axis. Consider an intersection in the (x, y) plane, i.e. a circle of radius r(z) at height z. Draw some electric field lines to a point on the z-axis... the symmetry will provide some cancellations. If you use an angle $\phi$ to parametrize the circle, then you can divide the circle into small segments of length $r(z) \, d\phi$ and write down the contribution to the E-field from each segment. Once you have that, all you have to do is sum (i.e. integrate) over phi.

Yes I know, it's a lot of work :sad: