Understanding Charge Distribution in a Spherical Shell

[sonutulsiani]

Homework Statement

I have a simple question.

There is positive point charge in the center of a sphere 2.5 micro c. The spherical shell has inner radius of 60 cm and outer radius of 90 cm. The net charge of the spherical shell is equal to zero.

Homework Equations

The Attempt at a Solution

Now the net charge = 0 :

Does this mean the 2.5 + charge on the inner radius + charge on the outer radius = 0?
Because that's what I did while solving the problem.

which gave me Charge on inner radius = -2.5 and charge on outer radius = 0

But the solution manual says that charge on the inner radius + charge on the outer radius = 0

which means Charge on inner radius = -2.5 and charge on outer radius = +2.5

 

[rl.bhat]

Positive point charge at the center attracts free electrons towards it resulting equal negative on the inner surface of the spherical shell. Initially the spherical shell is neutral. So the equal positive charge accumulates on the outer surface of the spherical shell because the charges cannot be present inside he metal.

 

[sonutulsiani]

But what does net charge mean? It means that all the charges present inside are equal to 0 in this case right?

 

[Mindscrape]

I'm guessing that the ambiguous language means there is no net charge within the sphere because all the charges have gone to the inner surface and outer surface. The outside surface should have a total charge of 2.5µC.