A hollow metal sphere has inner radius a and outer radius b. The hollow sphere has charge +2 Q. A point charge + Q sits at the center of the hollow sphere.

Determine the magnitude of the electric field in the region r≤a.

Explanation:

"Determine the magnitude of the electric field in the region r<a."

From Gauss' Law:

E(4?r^2) = +Q/?o

E = +Q/[(4??o)r^2]

"Determine the magnitude of the electric field in the region a<r<b"

The electric field inside of a conductor (with no current) is zero.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.