Demos
Instructors need to be very careful about how they use demos. Just showing a demo is no better than not doing a demo at all in terms of student understanding. In addition to possibly being difficult for all students to see in a large lecture hall even students who have a good view can convince themselves they saw what they expected to see not what really happened. Redish’s general method of using demos is as follows:
- Describe what the demo is to students and ask them to predict what will happen.
- Perform the demo and have students discuss what they saw.
- Perform the demo again (hopefully every now agrees what they saw).
- Have students discuss why the outcome is what it is.
- Perform the demo once more and summarize.
This entire process lasts approximately 30 minutes and starts looking like a cross between a traditional lab and a lecture. The actual labs students perform last two weeks and are fully student developed (students pick the question they wan to answer, they develop the experiment etc.) so classroom demos take on a sort of guided lab activity. There are also questions about the demos on the exams. Pam Kraus wrote a PER dissertation about demos at Univ. of Washington. Also see AJP 72 p. 835 (2004).
Misc.
- Because the labs are student generated grading the lab reports can be difficult. Each week Redish meets with all the lab TAs and they discuss how to grade that week’s lab reports.
- For fun try giving each TA in a group a solved problem or a completed lab report along with a grading rubric and have each TA grade the problem. Then have TAs discuss their grades and why they gave the points they did. You will be amazed how different the grades are even when the TAs are given a grading rubric.
- Elby Pairs are a way to teach students to enforce consistency. These are pairs of problems that look similar but where one problem is meant to be easy and answered correctly by most students and the other problem is mean to be more difficult and to illicit misconceptions. Both problems are based around the same physics concept so their solutions should be consistent.
- Renee Michelle Goertze (Univ. Maryland) has done some interesting work on what TAs and instructors think about results from PER. In Colorado (CU) everyone “gets it” and all the new TAs buy into research based teaching methods.
- Redish teaches Newton’s 0th law: Objects are egocentric, “me me me, now now now”. An object’s motion only depends on the forces on the object, at this moment.
- A main goal of Redish’s classes, particularly for non-majors is to teach students not to settle for 1 step reasoning. He wants students to go beyond their first impulse or applying the first principle or similar experiment they think of to looking for consistency between their answers to different questions or between their answers and all their cumulative experiences. Along these lines Redish spends the entire first week of the semester talking about psychology and how memory works to convince students it isn’t a good idea to settle for their first impulse.
- Arnold Arons has written many well regarded books on physics education.
