Solve the following questions:
Question I: How many excess electrons must be distributed uniformly within the volume of an isolated plastic sphere 24.0cm in diameter to produce an electric field of 1200N/C just outside the surface of the sphere?
Question II: What is the electric field at a point 12.0cm outside the surface of the sphere?
I am having a hard time understanding these questions. So if you answer please explain how you found the answers.