Warning! If you’re thinking this is going to be about gruesome punishments or such like, prepare to be disappointed! This is about teaching and learning electromagnetism.
Having recently retired, I am trying to keep my brain active. One thing I am doing is trying to grasp electromagnetism, which I never really got hold of either at school or university. At school, it was full of horrible formulae like the magnetic field inside a solenoid, and moreover it was taught in cgs units. Here one encounters two sets of units for all sorts of things, the electrostatic units (esu) and the electromagnetic units (emu). (I’ve already had a moan about Fleming’s Rules on Science 2.0).
If this is an emu, what does an esu look like?
Moving to university, suddenly I was confronted by vector notation, which I had never encountered before.
In later years, I got hold of the Feynman Lectures on Physics. Volume 2 deals largely with electricity and magnetism, and very good lectures they are too. But they don’t manage to repair every rotten plank in the attic of my understanding.
Then I discovered the Berkeley Physics Course (v. 2), this volume being Electricity and Magnetism by the Nobel Laureate Edward M. Purcell. ISBN 0070664951 (paperback) 0070049084 (hardback).
This book starts with four chapters on electrostatics, then chapter 5 introduces magnetism as the relativistic effect of moving charge, before moving on to magnetism itself and electromagnetism. Is that good? It’s certainly not something one would introduce at high school, but once one has got hold of even elementary Special Relativity it certainly does ‘demystify’ magnetism.
Which is, incidentally, the point of the late-medieval-looking illustration at the top of this article. It is the title page of Hypomnemata mathematica (1600) by Simon Stevin “Wonder en is gheen wonder” was translated by Ernst Mach as “every enlightening progress in science is accompanied with a certain feeling of disillusionment”. But I think that that’s an awful translation (Mach has the dubious distinction of being someone with whom both Lenin and myself find fault.) A much simpler translation is “Magic really isn’t Magic”
So am I recommending this book? Yes and no-ish. The matter is really summed up by the most helpful amazon.com Customer Reviews from Amazon. First, the favourable one:
Having used this book in college 24 years ago, I believe it remains the best overall introductory text book. It is written to truly give you understanding of the subject. In comparison, Halliday and Resnick, Feynman's notes, Jackson's (three of my favorite books) are respectively trying to teach engineering, provide insight, or impart mathematical rigor. Overall Purcell is not as original as Feynman but is a more complete and integrated coverage suitable for someone who wants to understand physics. It is not an engineering book so the problems are for thinking--really makes you think deeply about how the world is constructed. To solve lots of practical problems use H&R. Jackson is mainly useful to rounds out a few corners once you know the subject. I personally think it is the best intro book although the usual 10-12 weeks quarter or semester devoted to the teaching of this material is insufficient to really allow the subject to sink in--I'd take 3-4 weeks out over the summer and study this one subject alone before going to college. This will be extremely rewarding.And next, the critical one.
This is a (very heavily mathematical) introduction to the physics of Electricity and Magnetism. Although it has some strong points (It takes the time to explain the math behind div, curl, etc. and some of the problems are rather neat), it also has its weaknesses. First and foremost, the problems are almost universally without solution, except for a select few whose numerical answer are written below the problem. Combine this with the almost total dearth of examples, and you have a pretty serious problem for anyone trying to learn the material on their own. The sections themselves are also sometimes rather poorly explained. Chapters 5(explaining magnetism as the relativistic effect of moving charge) and 10 (dielectrics) are both fairly confusing and hard to understand. At times I found myself begging Purcell to include one, just one little measly example that could possibly make more sense than his pages and pages of writing. Once or twice I found myself not noticing that I had a fundamental misunderstanding of a facet of the material, just because no example or solution in the book provided a counterexample to my way of thinking.So, what point am I trying to make? This is a really good book, with some shortcomings. Apart from those mentioned in the critical review (it is quite a hard read on one’s WON) the other thing is my bugbear, cgs units. Either adopt SI units, or if not, use Imperial!
Today, plagiarism is a bugaboo, but really, it’s the arty lot that we have to blame for the idea that everything must be “one’s own”. Remember those school tests: “Express the following (from Shakespeare) in one’s own words”. But Shakespeare did it so much better!
But in medieval times it was not so. Ancient authorities were respected, and authors were judged by how faithful they were to the original. Purcell’s book is still in demand – the cheapest used copy on Amazon is 60$. So could someone please re-do it, addressing the comments in the critical review above AND USING SI UNITS!