# Electric Forces and Field HELP!

1. Nov 9, 2008

### kiplings01

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

While studying for ap physicsb, i came across this question and i'm so confused!

There's a sphere with CHarge C in the center of the sphere, and Point P on the surface of the sphere. There are three separate charges +q on the surrounding area.. The question is what affects the electric field on P?
-by the surrounding positive charges?
-the center of the sphere? etc

3. The attempt at a solution

I thought that electric field and charge of P would be affected by everything (+q AND C) because don't everything "emit" some Electric field on their surroundings. However, reading my textbook i find this "Conductor shields any charge within from electric field created outside the conductor....and E=0 conductor"

2. Nov 9, 2008

### Chi Meson

I am assuming that the three +q charges are at arbitrary locations outside the sphere, right? And point P is on the outside surface of the sphere?

OK, the general rule is that the solid conductor will shield anything inside its surface from an outside electric field. But if P is on the outer surface, then it is not shielded from the 3 +q charges. Depending on the arrangement of those 3 charges, the net affect will be varied, including one (maybe two) very specific arrangements that will cause the net field to be zero. Other than that, there will be a net electric field at point P due to those charges.

E=0 inside a conductor unless there is a charge in the space inside the conductor. If point P is on the inner surface of the sphere, then the electric field will only be due to C.

3. Nov 9, 2008

### kiplings01

Thank you so much! You cleared up a lot!