Finding E fields and potential given a hollow spherical conductor

[SeanLikesRice]

Hello, this is my first post here, so hopefully I do this in the right way...

Homework Statement

A hollow spherical conductor carries a net charge of 21.5 μC. The radius of the inner hollow is 5.2 cm and thee full radius of the sphere is 7.8 cm. At the center of the sphere, in the middle of the hollow, is a point charge of -12.2 μC.

Find the E field at a distance of 8.0 cm from the center of the sphere.

Homework Equations

E = \frac{kQ}{r^2}

The Attempt at a Solution

Now when I draw this up in my notebook, I'm a little confused. Since the conductor has a net charge of 21.5 μC, does the point charge of -12.2 μC not matter in terms of finding the E field?

Using the net charge...

E = \frac{k * 21.5μC}{(8.0cm)^2}

Is this correct, or d I have to account for the point charge in the center of the hollow sphere?

 

[haruspex]

Think about the distribution of charge on the conductor. What will the charge be on the inside surface?

 

[rude man]

Hello, this is my first post here, so hopefully I do this in the right way...

Homework Statement

A hollow spherical conductor carries a net charge of 21.5 μC. The radius of the inner hollow is 5.2 cm and thee full radius of the sphere is 7.8 cm. At the center of the sphere, in the middle of the hollow, is a point charge of -12.2 μC.

Find the E field at a distance of 8.0 cm from the center of the sphere.

Homework Equations

E = \frac{kQ}{r^2}

The Attempt at a Solution

Now when I draw this up in my notebook, I'm a little confused. Since the conductor has a net charge of 21.5 μC, does the point charge of -12.2 μC not matter in terms of finding the E field?

Using the net charge...

E = \frac{k * 21.5μC}{(8.0cm)^2}

Is this correct, or d I have to account for the point charge in the center of the hollow sphere?

What does Gauss say? Does he say it matters how the charge inside his surface is distributed?