Friday, December 13, 2013

Electricity and Magnetism

I have always enjoyed Edward Purcell’s textbook Electricity and Magnetism, which is Volume 2 of the Berkeley Physics Course. In fact, I love the book so much that I included it in My Ideal Bookshelf that I presented in this blog a few weeks ago. I own a copy of the first edition, with its orange cover that is now faded and falling apart. The second edition was published soon after I completed my undergraduate physics degree from the University of Kansas, so I have not used it much.

This year, a 3rd edition of the book was published, with coauthor David Morin (Purcell died in 1997 so he had no input on the 3rd edition). In the preface to the 3rd edition, Morin describes his goals:
“For 50 years, physics students have enjoyed learning about electricity and magnetism through the first two editions of this book. The purpose of the present edition is to bring certain things up to date and to add new material, in the hopes that the trend will continue. The main changes from the second edition are (1) the conversion from Gaussian units to SI units, and (2) the addition of many solved problems and examples.”
The use of SI units is interesting, because apparently Purcell resisted this change when preparing the 2nd edition. When I was an undergraduate around 1980, almost all introductory textbooks had switched to SI units, so I “grew up” with them. Therefore, I agree with Morin about the usefulness of this change. In the preface he writes
“The first of these changes [to SI units] is due to the fact that the vast majority of courses on electricity and magnetism are now taught in SI units. The second edition fell out of print at one point, and it was hard to watch such a wonderful book fade away because it wasn’t compatible with the way the subject is presently taught. Of course, there are differing opinions as to which system of units is ‘better’ for an introductory course. But this issue is moot, given the reality of these courses.”
The other big change is a lot of new homework problems and worked examples. This resonates with me, because one big change that Russ Hobbie and I made to the 4th edition of Intermediate Physics for Medicine and Biology is many new homework problems. Morin offers some advice to the reader in his preface, which applies equally well to readers of IPMB. In fact, one reason we only distribute homework solutions to instructors rather than students is to encourage students to struggle with these problems on their own.
“Some advice on using the solutions to the problems…If you are having trouble solving a problem, it is critical that you don’t look at the solution too soon. Brood over it for a while. If you do finally look at the solution, don’t just read it through. Instead, cover it up with a piece of paper and read one line at a time until you reach a hint to get you started. Then set the book aside and work things out for real. That’s the only way it will sink in. It’s quite astonishing how unhelpful it is simply to read a solution. You’d think it would do some good, but in fact it is completely ineffective in raising your understanding to the next level.”
One unique feature of Electricity and Magnetism is that magnetism is introduced as a consequence of electricity and special relativity. In almost all other books, this relationship is omitted or presented as an advanced topic. It is an interesting approach, about which I have mixed feelings. Morin writes
“The intertwined nature of electricity, magnetism, and relativity is discussed in detail in Chapter 5. Many students find this material highly illuminating, although some find it a bit difficult. (However, these two groups are by no means mutually exclusive!)”
If I was teaching our undergraduate electricity and magnetism class next semester, would I use the 3rd edition of Electricity and Magnetism? I would certainly consider it. In my opinion, its main competition would be David Griffiths’ textbook Introduction of Electrodynamics. I used that book last time I taught electricity and magnetism, and it is also outstanding. It is not cited in IPMB, which makes me rather sad, as it is another one of those much-treasured books. Just the thought of reading first Purcell and then Griffiths, trying to decide which to use, sounds so fun that I am tempted to volunteer to teach electricity and magnetism again.

For those wanting to learn more about Morin’s new edition of Electricity and Magnetism, read the interview with him on the Physics Today website. You can find a review of the book here. Additional information is on the book's website.

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