Course sequence, where to put E&M

Forgive me for double-posting if you already received this. It never reached me so I have to assume it wasn't sent.

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I like Robert Cohen's discussion of the sequence for introducing EM concepts. I must protest however that I neither invented nor advocate doing circuits first – although it may have its place. The CASTLE curriculum by Melvin Steinberg, now being distributed by PASCO, deserves that honor.

The electrical force - and electrostatics - can be introduced as part of mechanics. David Hestenes of ASU Modeling Method fame, in one of his lectures. presented the vision of distinguishing and characterizing the various kinds and manifestations of force as a part - the final part - of the study of Newton's laws. The standard Modeling curriculum does not at this point realize this vision.

Camp and Clement, in "Preconceptions in Mechanics", present a research-based and well-worked-out introduction to various manifestations of force: tension, compression including the "normal force", static and kinetic friction, and finally the gravitational force. Out of this they develop an effective treatment of Newton's third law, the failure to fully grasp which appears to produces the "70% barrier" in most modeling physics classes - the inability of most modeling instructors to achieve much higher than a 70% class average on the Force Concept Inventory (FCI). (Still way beyond what traditional instruction can achieve.)

Camp and Clement fall short however in not having a fully developed investigation of Newton's first and second laws and in structuring their curriculum so that it is still controlled from the front of the class. When I used their text straight my classes got restless and their comprehension and retention were limited.

The synthesis would be to weave their investigations and "bridging techniques" and the "modeling method" curriculum into a seamless, model-building, peer-instruction curriculum which includes careful investigation of the manifestations of contact force, buoyant force, the electrical force and electrostatics (introducing a primitive concept of current but without introducing the field, which is conceptually much more difficult), the force between two wires, and then the gravitational force - perhaps using a video of the Cavendish experiment with data generated but *no interpretation provided*. (Does anyone know of such a video? I was unable to locate one.)

Doing the electrical force first - and uncovering the inverse square law there - should help a lot in winning the students' grasp of the inverse square gravitational attraction. Finally then, starting with a reexamination of gravity as it occurs in a classroom, the concept of a field can be developed.

So we sneak a big hunk of the rest of physics into mechanics. In the process we deflect the criticism of spending too much time on mechanics - which we really needs to do if students are going to become Newtonian thinkers. This would give the students a good workout on the third law, and I expect we would break through the "70% barrier" on the FCI. In the process we would realize David Hestenes' vision of a mechanics course which truly forms a foundation for all of physics.

The next order of topics could be circuits a la CASTLE (or the Modeling Task Force rewrite of CASTLE to put it in a peer instruction project-based framework), then linking circuits to charges a la Sherwood and Chabay.

Thermodynamics is so essential to student understanding of energy and chemical phenomena that it should be included here. I would urge anyone to study the awesome article "Introductory Thermal Concept Evaluation" by Yeo and Zadnik in the November "Physics Teacher" for some insight into the central importance and challenge of tackling this material. (It is also a good example of the state of the art in concept test design!) Certainly if physics is to be a preparation for chemistry as in the "physics first" project this is a fundamental responsibility.

This would definitely fill a school year, and would be a year well spent.

Chris Horton

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