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2017 April 11

Maybe eliminate bench equipment next year

Filed under: Circuits course — gasstationwithoutpumps @ 22:40
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One of the BELS (Baskin Engineering Lab Support) staff had an interesting proposal for next year: maybe, instead of tying up a lab with $200,000 worth of bench equipment next year, the applied electronics course could have students rent a box containing an Analog Discovery 2 (with USB cable and power supply).  Each box would cost about $200, and students could rent them for about $30 a quarter (there is precedent for this approach—it is used in the first programming course for Computer Engineering).  As long as the failure rate for the USB oscilloscopes is low enough, the rental would cover replacement about every three years.  Furthermore, students could purchase the boxes at the end of the course for cost minus the rental rate.  Given the attractiveness of the instrument to bioelectronics students and to hobbyists, I suspect that about 1/3 of the boxes would get bought each year.

The initial investment is relatively modest (about $20,000 for 100 boxes) and the change would make it much easier to schedule the labs next year—all that is needed is a room with enough electrical outlets and enough tables and chairs (not even fancy lab benches).  We’d also need to have soldering irons and fume extractors, but those have already been purchased (though we may need to get more, as they keep getting used for other courses and other needs.

I’m now trying to decide between two options:

  • Stick with the conventional bench equipment we have.
  • Switch to using the Analog Discovery 2 exclusively (with maybe a handheld DMM for use as an ohmmeter)

The conventional bench equipment approach has the advantage of teaching the students how to use equipment that they are likely to see again in other courses or in research labs. The Analog Discovery 2 is not suitable for high-frequency work, so students going into work that need higher bandwidth will have to learn conventional bench equipment—the current course is the best training available to the students and helps them considerably in the EE lab courses, where they are expected to figure out the rather complicated bench equipment on their own. The bench equipment approach also requires no extra expenses for the students.

The Analog Discovery 2 approach has the advantage of allowing the students to do almost all the labs anywhere.  With the lab time for 5 sections coming to 16 hours a week, not having to share a lab with another course would be a welcome relief, both for us and for them.  (Also, we wouldn’t have to deal with all the damage that the untrained, unsupervised students in the first EE class do to the equipment.)  The Analog Discovery 2 provides an easier-to-use interface for all the equipment than the rather clunky old interfaces of the bench equipment in the lab—some of the labs that now take hours could be done in a few minutes, because of the better integration of the instrumentation. Furthermore, the students would be able to buy at very low cost a piece of equipment that would serve them very well in other courses and as hobbyists.

If we did go with the Analog Discovery 2, I would have to rewrite big chunks of the book to adapt the labs and remove (or separate to different sections) references to the bench equipment. I’m already planning to do a fairly major overhaul of the book this summer and fall, so that’s not a major argument one way or the other.

Faithful readers, advise me! Should I stick with the bench equipment or should I move to BELS renting out Analog Discovery 2 boxes next year?  What other factors should I consider in making the decision?

2012 August 31

Online physics—what about labs?

Filed under: home school — gasstationwithoutpumps @ 04:31
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I’ve often wondered how online courses handle labs.  Of course, in some fields (like computer science) the tools needed for doing labs are ubiquitous, and there are few safety concerns for doing the labs on your own.  In other subjects, like organic synthesis in chemistry, the safety equipment and supervision needed for many of the labs makes it imperative that students do the labs in a supervised setting.  In between are subjects like introductory physics and electronics, where it is possible to simplify the labs and use low-cost equipment to get most of the benefits of a lab course in a home setting.  More advanced topics in both fields start getting into equipment needs that exceed what an individual would want to buy or be able to borrow.

Since I’m home-schooling my son in calculus-based physics (so far we’ve mainly done mechanics, but this year we’ll be doing electricity and magnetism), I’m particularly interested in how online physics courses handle labs, looking for ideas that I can adapt for our own non-online course.  I found a recent paper by Ann Reagan, published by the Washington Academy of Sciences Online Introductory Physics Labs: Status and Methods.  This paper is a survey of online physics courses, attempting to find out what is being done.

In the intro, they reported 5 goals as desirable for physics labs, based on a position paper by the  American Association of Physics Teachers [“Goals of the Introductory Physics Laboratory,” American Association of Physics Teachers (AAPT), The Physics Teacher, 35, 546-548 (1997)].  Unfortunately, that paper is hidden behind a paywall.  At first I thought that even my university library’s subscription was unable to penetrate the paywall, but that was just bad implementation of the paywall, and I was eventually able to get a copy by editing the URL.  The goals in the original paper are listed as

Summary of Introductory Physics Laboratory Goals
I. The Art of Experimentation: The introductory laboratory should engage each student in significant experiences with experimental processes, including some experience designing investigation.
II.   Experimental and Analytical Skills: The laboratory should help the student develop a broad array of basic skills and tools of experimental physics and data analysis.
III. Conceptual Learning: The laboratory should help students master basic physics concepts.
IV. Understanding the Basis of Knowledge in Physics: The laboratory should help students understand the role of direct observation in physics and to distinguish between inferences based on theory and the outcomes of experiments.
V. Developing Collaborative Learning Skills: The laboratory should help students develop collaborative learning skills that are vital to success in many lifelong endeavors.
Many of the goals are not explicit in traditional laboratory programs. However, the American Association of Physics Teachers believes that laboratory programs should be designed with these five fundamental goals in mind.

I’m in agreement with these goals, though the “collaborative learning skills” will be somewhat limited with just my son and me working together.  (Last year we had another student in the course, but he graduated high school and went off to Pomona.)  I think that the collaborative learning aspects are the least important of the five goals for an intro physics course, as I’ve outlined in other posts on group work.

The first observation in Reagan’s paper is that online physics courses with labs are still fairly rare.  Only about 10% of colleges offered introductory physics online, and 40% of those required the labs be done on-site at the campus, often as intensive weekend or week-long “boot camp” experiences.  That leaves only about 6% of intro college physics courses as attempting fully off-site lab courses.  The paper identified 4 different approaches:

  1. Video analysis of instructor-provided videos.  The instructor designed the experiment, set up the equipment, performed the experiment, and recorded the results on video.  The students used video analysis tools (like the free tool Tracker, which I’ve made some modifications to) to extract data from the experiment and do the data analysis. (Meets goals III and IV, and the data analysis part of II.)
  2. Virtual experiments using simulations (like the well-regarded PhET simulations) are done, with the students interacting with a model of the phenomenon being studied. (Meets goal III and the data analysis part of II, has a flavor or goal I, but without real-world constraints.)
  3. Home experimentation using  loaned equipment or low-cost lab “kits”. (Meets goals I through IV, though only a limited set of the tools of experimental physics will feasible).
  4. Remote labs, where students interact with real equipment, manipulated remotely through the Internet.  (Meets goals II through IV.  Adding goal I would require extremely clever design of the remote operation interface.)

Of these approaches, only the on-site lab and the home experimentation provide the ability to meet the full range of goals. The colleges seem to agree as only 4 of the 400 sites surveyed had simulation-only “labs”.

My own experimentation with home-built equipment last year (see Physics posts in forward order for the full set of posts) leads me to believe that simulation is a terrible substitute for physics labs.  The real-world phenomena are not nearly as clean and simple as the models put into the simulations (even good simulations like the PhET ones), and learning how to get good measurements and model the data appropriately is the point of doing labs in the first place.  A lot of things that I thought would be simple turned out to have unexpected (by me) complexities. Finding ways to get cleaner data by changing the measurement method or the phenomenon being measured was an important learning experience, as was finding models for the actual observations.  Simulation is good for seeing what a particular model predicts will happen, but comparison to what actually happens is essential.

Reagan chose to explore the “kit” approach further, probably because she also believes that it is the only pedagogically acceptable alternative to the on-site lab (though she is careful not to say so).  She

limited consideration to experiments that 1) were relevant in scope and content to the curriculum of a first-semester introductory physics course, 2) were of appropriate complexity and depth for a college-level course, 3) would provide sufficient accuracy for student analysis and student satisfaction, 4) could be accomplished semi-autonomously by college students in a distance format (e.g., from home, communicating with instructors via e-mail or online chat, only), 5) required direct, hands-on interaction by students with the experimental process, and 6) could be accomplished with inexpensive or readily available materials at a total cost to students for ten such experiments commensurate with the price of a single textbook.

One suggested lab approach that I didn’t use last year, though I would have if I’d thought of it,  is using a microphone and sound software like Audacity for doing timing measurements.  She mentions timing dropped balls and bouncing balls by this approach.  It is probably easier to get clean data for estimating the coefficient of restitution from the times of the bounces than from the long exposure time digital photography method my son used in his fifth grade science fair project, though not as visually appealing. I think that our use of the Arduino for timing (for example, in the speed of sound  lab and the pendulum lab) was at least as effective, and did allow us to use triggers other than sound.

She also talks about using cell phone video cameras, frictionless pucks sold as toys, and Tracker video analysis for some of the other motion labs.  We did not end up doing much video analysis last year, because it was tedious and not well suited to any of the labs we ended up doing.  There were a couple of labs where it might have been a good idea instead of the methods we tried instead.

Interestingly, their first attempt at the Audacity lab for measuring the time for dropped balls was a failure in the real world:

Misunderstandings, misconceptions, and computational errors resulted in student-demonstrated percent errors ranging from 2% to 35%, despite consistent achievement of experimental errors of 1% to 2% in the same experiments carried out by the instructor.

They got much better results when they added video instructions for the labs that addressed common misconceptions and had the students working in a lab where they were observed by an instructor (even though the instructor was not supposed to answer questions). I wonder how much of the improvement resulted from the video instructions and how much from being observed.

 

2012 April 26

San Leandro fund-raising for AP Physics

Filed under: home school — gasstationwithoutpumps @ 22:46
Tags: , , ,

According to a Patch article, Advanced Physics Class $8,500 Away – San Leandro, CA Patch, an anonymous donor contributed $10,000 if the community could match it, in order to fund $20,000 worth of instructional materials and lab equipment to start an AP Physics class at San Leandro High.

While I applaud the donor(s) for trying to start a physics class in San Leandro, I wonder a bit at the price tag.  It is certainly possible to spend that much on high school lab equipment—I get the Pasco catalog and they do have some high-priced toys!  But it is also possible to teach AP Physics with much less equipment and with much cheaper equipment (even just changing to a lower-price vendor like Arbor Scientific can save a lot).  I’ve been home-schooling AP Physics this year and most of the equipment was stuff we had around the house. Even buying it all new would probably come to only $300, plus $90 for the textbook.

Granted, equipment designed to last several years in the hands of teenagers might need to be a bit more robust than what I could cobble together at home to last for one lab session, but I suspect that a class of 30 (about all they’re likely to get the first year) could be reasonably well equipped and provided with new textbooks for under $10,000.  I’m curious what the $20,000 will buy.

I’m also curious to hear from people who have been teaching AP Physics for a while.  How much does a decent (not luxurious) lab setup for AP Physics cost these days?  I suppose there are several components:  consumables (1/student every year), textbooks (1/student, good for 5–7 years), student lab equipment (1/group of 2–3 students), classroom equipment (1/classroom), and school-wide equipment (1/school).  What I’m interested in hearing how the budget is divided among the different components.  Put another way—if you had $20,000 to start an AP Physics class (for equipment and materials, not staff), how would you spend the money?

My expenses have been small in part because I don’t need much “demo” equipment—nothing needs to be seen from the far side of a classroom, so I can use little things rather than big ones.  I also had the luxury of having students who were good at math—they already knew how to visualize and add vectors, so I did not need to do all the force table demos and labs.  I was also limited in the time I had with the students (2 hours a week to cover all the material, do the labs, and check the homework), so I may have shortchanged the students a bit on labs. I hope they got enough good lab experiences, and we’re going to do almost all lab stuff after the AP exams, but I do wonder if they would have gotten more useful lab work in a traditional class.

Of course, a big part of savings comes from the simple fact that I’m cheap.  For a one-time lab, I’d rather duct-tape together something that works well enough than pay hundreds of dollars for the shiny Pasco toys, as fun as they are to look at in the catalog.  (Since I’m an engineering professor, they send me the “Engineering” catalog, which I think has even fancier and more expensive building toys than the “Physics” catalog.)  It may well be that the time it takes to make and debug jury-rigged equipment would make it more expensive than the commercial stuff, if a teacher or other staff person were actually being paid to do it, and if the labs had to be run year after year.

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