Over at Jim Henley’s place, Thoreau further justifies his status as an essential academic-physics blogger with a really good post about the problem of introductory labs:
In freshman labs, generally you?re trying to measure something (at least as it?s done at many schools). The measurement is never as clean as the stuff being taught in lecture (or interactive discussion-based peer-involved blah blah whatever). There is nothing wrong with the fact that lab measurements are not as clean as the stuff in lecture! However, it does mean that you aren?t spending those 3 hours thinking about the same things you were thinking about in lecture. I mean, yes, there?s probably a rotating object (or whatever) in the lab, and the professor?s diagrams in lecture probably also had a rotating object. But in lab you?re thinking about the best way to measure the tensi0n in that spring and trying to figure out whether the biggest factor dominating your uncertainty is the difficulty of keeping the system stable or maybe it?s the fickle nature of this meter you were using, and then you have to remember to subtract out this other force in your data analysis, and set up your data table correctly.
After two and a half hours, if all goes well, you get a graph that involves force and angular velocity or something, and that graph might even look like the graph that your professor produced in lecture when explaining some concept about rotational motion.* You are now ready to start your write-up and answer some questions before the 3 hours are up. However, you didn?t spend two and a half hours thinking about rotational motion. You spent two and a half hours trying to get this device to be stable and whatnot. Odds are that you didn?t learn anything new about rotational motion in that time. If things were done right, you probably did learn something about how to troubleshoot a tricky instrument.
He’s absolutely right about the problems here. In fact, this problem extends beyond the introductory level– no matter what the level of the lab class, labs present a significant problem. There are three things you might hope to accomplish in a lab class, and those three goals do not coexist peacefully.
The three goals of a lab class are, in no particular order:
- To teach students lab skills (how to use equipment, how to make measurements, how to record and analyze data)
- To complement the physics taught in lecture (either by providing a direct example of the physics discussed in class, or by exploring applications that aren’t covered in class)
- To teach students something about scientific writing (through writing lab reports)
These goals conflict with each other, in that trying to pursue one of them creates problems for the others.
If you want to teach students how to write, you necessarily need to have them do a lot of writing, which argues for doing as many labs as possible. On the other hand, if you want to teach lab skills, you need to give them time and freedom to experiment with the apparatus, which means doing a smaller number of longer labs. If you want to complement the lectures, you need labs that will reliably give something close to the theoretical prediction (as Thoreau notes), which argues for relatively “canned” labs, with minimal opportunities for students to mess up the apparatus.
You can sort-of satisfy two of these, by having students do lots of “canned” experiments and write them up, but the only lab skill that teaches is how to follow precise directions, which is not actually that useful in research (or anything else). There isn’t really a good way to do all three, though, and I’m not convinced that writing up “canned” experiments actually teaches that much about scientific writing (though this may be because I hate grading large numbers of reports whose procedure sections are basically copied from the lab hand-out).
This is a Hard Problem, and I don’t have a good solution to it. Anybody who does have a good solution, please leave a comment telling me what it is, because I would love to know.