Teaching to the test
I suppose I'm going to do it today, despite feeling terribly guilty about doing so, given that it violates all the Principles of Good Teaching I've been raised to believe in.
The reasons for this are manifold, I suppose. Principally, it's because last time, I focused on the main concepts, like, y'know, we're supposed to, and my students got nailed because our professor decided to include something which I had made a conscious decision not to cover, because I thought it was too unimportant in the grand scheme of things (and I was right, dammit). So I want to make up for that.
But more fundamentally, it's not really the professor's fault, either. When you get down to it, the number of solvable problems in elementary E&M is extremely small. (Not as small as in introductory QM, but still quite small.) So you're faced with two choices: either ask one of the basic problems, which have (hopefully) been already covered a multitude of times, or add in some twist which requires knowledge of something which is pretty irrelevant, but at least makes the problem nontrivial. Our professor seems to have chosen the latter option, because it does at least produce a wider spread of scores, which makes the all-important grading that much easier.
I could add in some more cynical comments, but I think I've already exceeded my quota for this post, plus I need to actually work on writing aforementioned teaching for the test, so I'll be quiet now.