Question

A hollow sphere has a uniform volume charge density of 4.61 nC/m3. The inner radius is a = 14.6 cm and the outer radius is b = 43.8 cm.

What is the magnitude of the electric field at 21.9 cm from the center of the sphere?



What is the magnitude of the electric field at 140. cm from the center of the sphere?

Answer 1

simple> Figure the total charge enclosed at the given r, then consider that a point charge at the center, E=kQ/r^2

Now on the volume of charge, remember it is a hollow, so figure the total volume of sphere, then subtract the empty volume, then multiply by charge density.
Look up Gauss' Law