Electric field of point charge within spherical shell.

1. Sep 24, 2014

malignant

If there was a spherical shell with negative charge density and a positive point charge inside the shell, the electric field lines from the point charge would just be radially outward towards the shell right?

What about the case where there's a positive charge density and a positive point charge? I'm having trouble conceptualizing what happens to the field lines from the point charge then.

2. Sep 24, 2014

Staff: Mentor

Do you mean a hollow shell with a uniformly distributed negative charge? Then yes.

Ask yourself: What field does the shell's charge contribute inside the shell?

3. Sep 24, 2014

malignant

Isn't the field inside from the shell's charge zero leaving just the field from the point charge? Or would the field from the shell and the point charge have to be summed?

4. Sep 24, 2014

Staff: Mentor

Yes.

Yes. (But the field from the shell is zero. ;))

5. Sep 24, 2014

malignant

Ok but where do the field lines go from the point charge? If it doesn't escape the shell due to the positive charge on the shell repelling, and no lines can intersect, it sounds like the field would end up being infinitely dense.

6. Sep 24, 2014

Staff: Mentor

Outside the shell, the field will be the sum of the fields from the point charge and from the shell. (The field from the shell is zero within the shell, but not outside the shell.)