A solid conducting sphere of radius 2.00 cm has a charge 16.00 µC. A conducting spherical shell of inner radius 4.00 cm and outer radius 5.00 cm is concentric with the solid sphere and has a total charge of -3.00 µC. (Take radially outward as the positive direction.)
Find the electric field at r = 4.50 cm from the center of this charge configuration.
The Attempt at a Solution
I think there's something wrong with my physical picture. So before I get into any calculations, this is what I'm thinking.
Since they are conductors the charge can move around. The inner sphere is positive so it will attract the negative charges from the outside of the outer sphere to the inside, leaving the outside of the outer sphere positive.
Therefore, the net charge within the enclosed Gaussian should be Qin=+13μC.
However, that doesn't seem to yield the correct answer.