I just finished my unit on circuits in Physics 132 and, along the way, discovered a useful tool for helping biology students grasp the importance of completely understanding and memorizing a mechanism.
In physics, we often consider memorization to be a “dirty word.” We pride ourselves on being the discipline that doesn’t require much, if any, memorization. In fact, many physics instructors I know will say, “I don’t want them to memorize.” We provide equation sheets and other memory aids in many physics exams. Usually, this aversion to memorization comes from a reasonable place: I think the aversion to memorization ultimately comes from the idea that we don’t want students’ inability to recall certain facts to get in the way of the problem-solving skills we actually care about.
However, I’ve come to the conclusion over the last couple of years that this disciplinary cultural aversion to memorization has perhaps gone a bit too far. There are certain facts that you do just need to know in order to solve problems. Many points in the literature emphasize the importance of teaching and mastering conceptual understanding upstream of the problem-solving process. This is the entire motivation behind Eric Mazur’s introductory physics textbook and the main takeaway from Paul and Webb’s paper, which advocates the same approach.
If we therefore accept that conceptual understanding is foundational to problem-solving success in physics, then it follows that students must actually remember certain fundamental physical facts. This is relevant in my circuits unit, where I continue to use a series of questions I developed 15 years ago involving the physical processes involved in charging capacitors: consider the voltage drops along wires (you can’t consider wires to be ideal, resistance-less conductors for this exercise), how those voltage changes can also be viewed as electric fields, and how those electric fields exert forces on the charges already present in the metal thereby charges the capacitor.
While teaching this sequence this past semester, I had a sudden inspiration in class, which I acted on. I told the students, after we had completed the sequence, that this series of questions and the underlying logic therein was effectively the “Krebs cycle for capacitors,” and that they really needed to know these steps.
Using the phrase “Krebs cycle” truly seemed to resonate with the students. I saw many nods of understanding that I had not seen before, nods indicating that they understood the importance of memorizing the sequence. Moreover, there was a slight giggle in the room, so I asked, “Y’all just surprised that a physics instructor knows the Krebs cycle?” Several of them said yes. I think that this reference to a fundamental biological mechanism served multiple purposes in promoting authenticity. I used the language of biology to emphasize that we were talking about a mechanistic process similar to the ones with which they are familiar and have experience memorizing. Moreover, the Krebs cycle is foundational, and so calling the series of physics steps that underpin capacitor charging a “Krebs cycle” showed the students, in a biologically authentic way, the importance of what we had just discussed.
Now, of course, I don’t yet know the effects of this reference, but I’ll be watching in office hours over the coming weeks to see the number of questions coming in about the capacitor-charging process. Unfortunately, I don’t have a lot of notes with which to compare from prior years, but often this process results in a lot of questions during office hours. If most students now seem to have grasped the process, I will consider it a beneficial step. Even if there’s no change, the use of a biologically authentic phrase such as “Krebs cycle” is, I think, a useful tool when teaching introductory physics for life sciences.