Today’s episode of “Thrilling Tales of Physics Pedagogy” is brought to you through a comment by CCPhysicst who picks up on the implications of last week’s schedule post:
You are ripping right along in that course. You do E and then B and only later get around to circuits?
Yes and no. We are ripping right along, because our insane trimester calendar demands it. We’re not ripping along quite as rapidly as this might make it seem, though, because we’re using a new curriculum based on Matter and Interactions by Ruth Chabay and Bruce Sherwood. It approaches topics in a somewhat idiosyncratic order.
Volume II, covering the traditional E&M areas, starts off with electric fields (Coulomb’s Law was covered in Volume I) and electric dipoles, then talks a bit about charging and polarization of materials, then distributions of charge. After dealing with solid objects, it moves on to electric potential, then to magnetic fields and Biot-Savart, before returning to electric circuits for a couple of chapters, and then moving on to magnetic forces on particles.
That’s not all that much like the standard order of things, but it does mostly work. There’s some internal logic to the order of topics, and it does have the nice effect of putting most of the scaaaary integrals close together (distributions of charge, electric potential, and Biot-Savart all involve integration, so doing them in successive chapters keeps students on top of the techniques).
Of course, the fact that there is some internal logic doesn’t mean that it all makes sense. In particular, the jump from Biot-Savart back to electric circuits just feels weird, and then they split the circuit topics up over two chapters in a way that feels kind of strained to me. I’m sure it makes perfect sense to them, but it feels really artificial and arbitrary to me.
This is a problem I encounter all the time with textbooks, though. I have a similar problem in the standard classical mechanics course, where most books spend an entire chapter on work and the “work-kinetic energy theorem” before introducing potential energy and conservation of energy. That’s never made much sense, either, and has always felt more like a result of an imposed need to break the material up into chapters that each take one week to cover, rather than a natural break point in the material. It takes about a week and a half to cover all of work and energy, so they’ve padded the “work” section out a bit, and made it a chapter in its own right.
After hemming and hawing quite a bit, I decided to punt on the circuit stuff, in more or less the same way I do regarding work and energy in mechanics. I’m spending this week and part of next jumping back and forth between Chapter 18 and Chapter 19 in the book, in order to cover the circuit topics in a way that I’m comfortable with, rather than forcing myself to follow the book exactly, and giving lousy lectures as a result.
I rationalize this by saying that it provides students with a different take on the same material, so they’re not in the classic bind of having identical explanations in the textbook and in their lecture notes, with no way to shed light on the subject if it doesn’t “click” from that one explanation. (The classic “Don’t take a class from a professor who wrote the book” problem.) This is a blatant rationalization, though.
I generally like the book, for what it’s worth. It consistently takes a microscopic view of the physics under discussion, which is a refreshing change in perspective. More importantly, the language and approach are very different than the standard intro treatment, so we’re not lulling students from AP Physics to sleep with familiar-looking material, but challenging them to actually think about what’s going on.
The different approach does make occasional trouble for the faculty, though…
Thanks for the report from Matter and Interactions. I’ve looked through the books, but we haven’t implemented them here yet. I have, though, been trying to use vpython quite a bit in the intro labs, so I am wondering how much of that you use
in teaching with this book. I have seen some pretty cool demos, particularly of E&M waves, but am really curious to hear your experience (provided you have time to give it).
Question up front:
You never told me how your students score on the FCI at the start of physics 1, or the math prereq for the course you are teaching now.
Thanks for the commentary. I can’t use that book for structural reasons (it matches up really badly with our articulation agreements), but the ideas are interesting as are your problems with it. I steal ideas from a lot of places. You can see my general comment about DC circuits in the bottom paragraph.
That book would have worked for me (we used the Berkeley 2 text by Purcell), but we had calc III as a pre-req for my first-year course. The highly conceptual load at the start of E+M (Gauss’ Law and applying integration) requires a lot of my students, and they seem to grasp Ampere’s Law better after those ideas settle in for awhile. I sometimes teach Ampere (or even a point-current formula akin to Coulomb’s Law for point charges) before Biot-Savart for a similar reason.
I’d suggest looking at Knight’s book. IIRC, its structure follows a typical quarter system format (lumping thermo, waves, and optics into the third quarter) and its pedagogy is pretty good.
I am using Wolfson’s “essential” book and love it. Students were saying things like “I skim it before class” in the exit comments, which is unheard when using the longer and more, errrr, turgid texts in the past. He splits DC circuits in a strange way that makes my “R before C” reordering a bit more awkward than usual, but I figured out how to do it better next semester. BTW, although I moved R before C before I saw how Redish et al introduce R first, I now use that approach (a connection from potentials to batteries to circuits) and it works really well. Also gives me a chance to slip in one more V = integral of E example.
Question up front:
You never told me how your students score on the FCI at the start of physics 1, or the math prereq for the course you are teaching now.
The pre-test FCI scores for the classes I have easy access to average to 16.6. That’s for three different terms, a total of 53 students.
The course I’m currently teaching is the second term of the introductory calculus-based sequence. Multi-variable calculus is at least a co-requisite for the class. Because we’re on trimesters, I’m not sure how to map that onto a traditional schedule.
I’ll have to look for Knight and Wolfson. We just changed to M&I this year, so won’t be switching again for a little bit, but I can usually find some tips in new books.
I’ve been using Chabay and Sherwood for the past four (or was it three?) years. I think your comments are just about right. I’d add that I get the impression that they really started to run out of steam ’round about Chapter 22 where the number of examples and exercises and problems becomes meager, and the pages-per-concept seems to dwindle. The presentation on entropy is especially good. I find irksome their insistence on rejecting certain standard language such as “heat”, and standard concepts such as “field lines”. Thus for the forseeable future there will be a mismatch between this text and standardized tests. There are also still a few mistakes and wanderings of logic that I’m sure will be cleaned up in the next few editions.
I have FCI data from the first day of class and the last day of mechanics for each year. The data are in a bit of a shambled state, but it looks like Chabay and Sherwood does about the same as more traditional books. I’ll use it at least one more year. At that time I’ll reconsider all options.
I’ve also used HRW, Cummings, Knight’s preliminary edition, and Knight’s first edition. The students don’t like any of them. They especially don’t like Chabay and Sherwood because it’s hard to track down the answer to specific questions. Students must read it with active engagement, something that they just don’t do.
I was completely delighted with Knight’s preliminary edition, but I actually dropped the first edition at the winter semester break. The layout was too visually stimulating with boxes and whatnot. Students complained that with all the junk floating around on the pages, it took five pages to make one simple point. I agree. In the chapter on kinetic theory the variable tau was used to represent two different time quantities in the same derivation. Worst of all from my POV was his elimination of the section on “forces that do no work”, and his backward step of introducing potential energy in terms of gravity at the earth’s surface (in 1st ed.) rather than as the energy of interaction of two object (prelim. ed.).
CCPhysicist hits it on the head for me. Choice of books is rather irrelevant if they only open it to see which problems you’ve given and what the answers in the back are…
FCI. Wish I’d remembered to print that off and do it on day 1.