1: Conceptual problem, looks for understanding of electrical insulation/conduction and electrostatic shielding. Very nice problem for exam. Low moderate difficulty in my opinion.

2: Spherically symmetric Gauss’s Law problem with a non-constant charge distribution. This was an exam problem last year. Few students did well on it. It was a difficult problem because the variation of the charge density with r forces you to do the integral in order to figure out the total charge enclosed in the spherical Gaussian surface. However, if you realize that one must do the integral, the problem is really fairly simple to do. Most people ignored the radial dependence of the charge distribution and treated it as a constant throughout the volume because that is what was done explicitly in the example we did in class. I’m hoping this kind of preparation will change things … but my thinking at the moment is that any problem that requires you to set up and evaluate an integral will be rather difficult for most of the class.

3: Conceptual problem I thought interesting. It serves as a point of departure for a discussion of electric potential and electric field and their relationship. This problem might be a stretch for an exam.