QUESTIONS 5.The electric field E is zero at all points on a closed surface; is there necessarily no net charge within the surface? If a surface encloses zero net charge, is the electric field necessarily zero at all points on the surface? 6.Define gravitional flux in analogy to electric flux. Are there "sources" and "sinks" for the gravitional field as there are for the electric field? 8.A spherical basketball(a nonconductor) is given a charge Q distributed uniformly over its surface.What can you say about the electric field inside the ball? A person now steps on the ball, collapsing it, and forcing most of the air out without altering the charge. What can you say about the field inside now? 12.A conductor carries a net positive charge Q. There is a hollow cavity within the conductor, at whose center is a negative point charge -q. What is the charge on (a)the outer surface of the conductor and (b) the inner surface of the conductor? ATTEMPT 5.----I think the first one is yes because according to Gauss's Law, if a surface enclose net charge, E at points on surface would not be 0; as for the last one, I think it is wrong because even though there is no sinks or sources in a closed surface, electric field lines are still allowed to pass through the surface, which results that E at some points on the surface is not 0. 6.----I think anything that has mass can be considered as "sinks", but how about "sources"? 8.----At first, the field is determined the Gauss's Law. After collapsing, the field doesn't change because of no loss of charge. 12.----I think both are 0. For the outer surface, the net charge it enclose is 0, so that E on the surface is 0.