John, the depth and breadth of your physics knowledge and understanding is
much appreciated by participants in this forum. However, you often make odd
pronouncements about the calculus-based intro course concerning what is or
is not appropriate, or what does or doesn't work, which seem to be highly
theoretical and not grounded in experience nor justified with data. You
have repeatedly been asked to explain what your experience with this course
actually is, and you have repeatedly ignored the question, which suggests
that you have none.
The reason why I claim that our teaching of a micro as well as a macro
model of DC and RC circuits is "successful" is based on several sources:
1) I taught the calculus-based intro physics course for 42 years at diverse
institutions -- Caltech, Illinois, Carnegie Mellon, and NC State. This
provides a strong basis for multidimensional judgements from experience on
what works and what doesn't.
2) When we initially attempted teaching about charge and field in circuits,
stimulated by the writings of the German physics educator Hermann Haertel,
we failed. The attempt was unsuccessful. After revisions we found an
approach that was successful, and the evidence that it was successful was
based in part on how different the outcomes were from the previous
attempts. The comparison provided one kind of metric.
3) Unknown to us before the work was published is the study described in
the article "Macroscopic phenomena and microscopic processes: Student
understanding of transients in direct current circuits" by Beth Ann
Thacker, Uri Ganiel, and Donald Boys, American Journal of Physics 67, S25
(1999); doi: 10.1119/1.19076. From the abstract: "One group studied from a
traditional text, the second group used a recently developed text that
emphasizes models of microscopic processes. We also conducted detailed
interviews with some of the students. From an analysis of the performance
of these two groups, and also from a comparison with a previous study on
Israeli high school students, we found that most of the students whose
instructional experiences included an emphasis on the development of models
of microscopic processes developed a better understanding of the transient
phenomena studied. They applied qualitative considerations in their
analyses and were able to develop coherent models to describe their
observations. Overall, they demonstrated a superior understanding of the
physical phenomena." The "recently developed text" was the early 1995
version of our E&M volume (which has been significantly improved in later
editions).
In the conclusions section the authors say the following, where A is the
group using a well-regarded traditional textbook and B is the group using
our book:
"We found that group B students exhibited a superior understanding of the
phenomena and were better able to give valid explanations in a variety of
situations, including those which were less familiar to them, than group A
students."
In summarizing interviews with students from the two groups, the authors
say this:
"Students (from group A) would search for replies that would utilize
phrases (and even equations) they had encountered, rather than try to base
their response on a mental model of the physical situation. Some students
even failed to see when they were contradicting themselves, but this was
not always the case. Of the 20 students interviewed, 2 students
demonstrated a very solid understanding of the concepts, an ability to
think through an answer by analyzing a microscopic model, and the ability
to build a new model when a failure in the one they were using became
evident. However, one of these students had two years of high school
physics and the other had two years of community college before taking this
course.
The interviews with students from group B were quite different. When they
did not initially know the correct answer, they would recognize
inconsistencies in their models and were able to construct models based on
microscopic processes easily. The idea of charge "jumping" from one
capacitor plate to the other came up in two of these interviews, but it was
quickly dispelled."
4) Less compelling but not irrelevant is the large-scale study "Tale of two
curricula: The performance of 2000 students in introductory
electromagnetism" by Matthew A. Kohlmyer, Marcos D. Caballero, Richard
Catrambone, Ruth W. Chabay, Lin Ding, Mark P. Haugan, M. Jackson Marr,
Bruce A. Sherwood, and Michael F. Schatz, PHYSICAL REVIEW SPECIAL TOPICS -
PHYSICS EDUCATION RESEARCH 5, 020105 (2009). In this study the gains on the
BEMA assessment of basic concepts in E&M were significantly larger in
comparisons made at Georgia Tech, Purdue, NC State, and Carnegie Mellon,
but circuits is just one of the topics in this assessment.
John, you have missed important caveats in our chapter on the role of
surface charge. We are quite explicit that we ask students first to sketch
the patterning of electric field in simple circuits, based on the node rule
(charge conservation in the steady state) and the loop rule (the round-trip
integral of the electric field is zero). An important tool is that the
conventional current in the Drude model is I = qnAv = qnAuE, where n is the
carrier density, q the carrier charge, A the cross-sectional area, v the
average drift speed, u the carrier mobility, and E the electric field. We
then ask them only to show very rough indications of surface charges that
are not strongly inconsistent with the patterning of electric field, and we
are explicit about these charge distributions being in reality quite
complicated. You assert without proof that all of this is worse than
useless, but the study by Thacker, Ganiel, and Boys says otherwise.
Also, it is important to reiterate that we do analyze DC and RC circuits
from the macro viewpoint as well as from the micro viewpoint. It's not that
we have replaced the macro model with the micro model. It can be useful to
look at important phenomena from more than one point of view, as has been
proven to be the case in this instance.