1. The net electric flux passing through a Gaussian surface is found to be positive. Which of the following statements is correct?
[A] The net charge outside the surface is positive.
[B] The net charge inside the surface is positive.
[C] The net charge outside the surface is negative.
[D] The net charge inside the surface is negative.
2. An insulating sphere of radius a is uniformly charged with total positive charge Q. An insulating spherical shell is placed around the charged sphere. The shell's inner and outer radii are b and c, and it carries a uniformly distributed net charge -2Q.
(a) Find the electric field (magnitude and direction) inside the shell (b<r<c). Begin with a statement of Gauss's Law and indicate in the diagram your choice of Gaussian surfaces.
(b) If the outer shell were a conductor instead of an insulator, the electric field inside would be zero (be sure you can justify that statement). If the outer shell were a conductor with a net charge of -2Q, how much charge would be distributed on its inner surface? Use Gauss' Law to justify your answer for the inner surface. How much charge would be distributed on its outer surface? Use conservation of charge to justify your answer for the outer surface.