What is New in the Third Edition
The primary goals for the 3rd edition were
The following is a list of changes that affect all units:
Here is a list of important changes in the 3rd edition of unit C:
Unit N did not receive much modification compared to most of the other units, but users of the 2nd edition will noted these changes:
Unit R also received only a handful of changes:
This unit was completely rewritten for this edition, almost from scratch. It therefore bears little resemblance to the 2nd edition, and though it is a bit closer to the "draft 3rd edition" that has been available for some years, it is still very different.
The core goal for this unit was to reduce the pace by about 30% compared to either of the previous editions. The author, after consulting with a number of users, has done this by cutting about 20% of the material overall (mostly by streamlining and reorganizing the presentation) and spread the remaining material over 18 chapters instead of 16.
Another goal was to provide more flexibility. Chapters E7 and E14 are now optional, so a professor can still teach the unit in 16 class sessions if necessary. Indeed, chapter E11 now presents the unit's "great idea" and nothing beyond this chapter is needed for any unit, so in principle, one could present a fairly easy version of this unit (without Maxwell's equations) in 10 or 11 class sessions. Professors also have more freedom to choose the level of the class by choosing the types of homework problems and class activities.
Unlike the 2nd edition, but like the "draft 3rd edition," this unit focuses on the differential versions of Maxwell's equations without ignoring the integral versions). However, the author has taken advantage of almost a decade of teaching from the "draft 3rd edition" to improve the pedagogy in many ways, making the presentation significantly simpler. Most importantly, multi-part problems E12M.1 and E13M.1 walk students step-by-step through the process of calculating fields using Gauss's and Ampere's laws (respectively) for non-trivial situations. We have found that having students work these problems as class activities makes a huge difference in their comfort level with these laws. After we made this change, students given instruction in both the differential and integral forms and given the choice of which to use on a test question almost universally chose to use the differential forms (and most used them correctly).
The integral treatment now appears in the optional chapter E14. This chapter is also significantly simpler than the corresponding material in the "draft 3rd edition." The connection between the differential and integral forms is only discussed at an intuitive (rather than a detailed) level, and a new approach to naming the pieces of gaussian surfaces and amperian loops makes talking about how to construct these surfaces much easier. Even though this chapter is optional, the concepts of line integrals and flux integrals are now more carefully developed in chapters E3 and E5 in the context of potential and current (respectively), where the application of these ideas is somewhat more concrete.
The introduction to waves now appears in unit Q. Chapter E18 on electromagnetic waves no longer requires this. This move also makes unit Q able to stand on its own without requiring that unit E precede it.
Other changes (particularly from the 2nd edition) are so numerous that a list similar to what we have presented for the other units would not be very helpful. Look instead at the table of contents and better yet, study the text of the unit itself in some detail to see all the differences. However, we will say that teaching this unit in draft form over the past few years has a been significantly better experience than with any of its previous incarnations.
This unit has also been significantly revised from the 2nd edition. In addition to the overarching goals for the new edition, one of the most important goals for this unit was reorganizing the material on spins (gathering material scattered over the unit into one place) and breaking the old chapters Q5 and Q6 into more manageable pieces. We also wanted to move the material on waves from unit E to this unit so that it could stand more easily on its own.
In our teaching experience, complex numbers proved to be an annoying and unnecessary distraction for introductory students. Though most students claim to have seen complex numbers in high school, students had much more difficulty using complex numbers than the author imagined when writing chapter Q5 for the 2nd edition. Over the years since that edition, we have found ways to teach the basic material (even time evolution) without complex numbers.
With this in mind, here is a list of important changes for this unit:
Adding this material to the unit required some deletions to keep the length and pace manageable. The most important deletions include:
This unit covers most of the same material as in the 2nd edition, but its presentation has been significantly reorganized, both for clarity and for the sake of flexibility.
Besides grouping the material in a more organized way, this reorganization gives the professor more flexibility about what to include. Chapter T1-T3 now provide a complete treatment of the unit's main idea. Chapter T4 adds valuable material about the Boltzmann factor and T5 adds valuable material about ideal gases. One could therefore provide a very decent introduction to thermal physics with just these five chapters. One can even split unit T into two separated halves to better fit a given calendar.
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