In putting together the book for this quarter, I added exercises to some of the chapters, and I assigned a chunk of them due today as the pre-lab exercise for the microphone lab. I just spent over 3 hours grading the set, just marking questions right or wrong. There were too many questions, and even the best in the class got only 8/11, with the bottom of the class getting 3/11. I think that the class is doing better this year than previous years’ classes, but some of them got discouraged by how much and how difficult the homework was. The amount was certainly more than I had intended, but next week’s homework should be substantially less. I’ll have to figure out how to distribute the load more evenly next year.
I spent most of today’s lecture going over two of the questions (in response to student request), and I’ll have to do some of the other ones on Wednesday, in addition to showing them how to model DC behavior of the FET in the electret microphone. I may also ask the group tutor for the class to have an extra help session this week. The two questions that got asked about were the modeling of the oscilloscope probe and computing the sensitivity of the electret microphone circuit with a different load resistor.
Some of the problems students had were ones that can be easily fixed (like that 1/10000 is 0 in gnuplot, because it looks like integer arithmetic—1/10E3 does the right computation, as does 1./10000). Other problems were fundamental misunderstandings of complex numbers or complex impedance, which may be harder to address.