Copyright © 2014 jsd

John Denker

1  Introduction

For starters, the University Physics book a) explains entropy in terms of "disorder", and then b) defines entropy in terms of dQ/T.

I reckon nobody is going to understand thermodynamics in general – including (!) the argument about the sign that appears in Ohm’s law and Lenz’s law – until they unlearn both (a) and (b).

Seriously: A’) Disorder (to the extent it can be defined at all) is a property of the microstate, whereas entropy is a property of the macrostate, a property of the distribution. Specifically, it is an ensemble average of the surprisal.

B’) There is no such thing as dQ (except maybe in trivial cases). As Thomas A. Moore so aptly put it, dQ is a crime against the laws of mathematics.

There are some students who can learn by rote some of the key results in thermodynamics, but even that is an iffy proposition, and more importantly if you care about /understanding/ then AFAICT you have to get rid of "disorder" and "dQ".

As a separate issue, the book says there are two kinds of electric charge (which is wrong) and credits Ben Franklin for naming the two kinds (which adds insult to injury). Franklin rightly insisted there there is only one kind of charge, and coined the names positive and negative for precisely this reason, to emphasize a difference in /amount/ ... not a difference in kind.

The book attributes to Einstein the "principle of relativity" ... even though Galileo set forth the principle with exquisite clarity more than 250 years before Einstein came on the scene. I’m not sure this counts as wrong physics, but it is certainly wrong history. Physicists do not have a license to falsify historical facts, just as historians do not have a license to falsify physical facts. Besides, why mention it at all, if you can’t be bothered to get it correct? This sort of thing is a huge disservice to students, because it gives them a false impression of how science is done.

The book proceeds to present a version of relativity that has been obsolete for more than 100 years. Again I’m not sure this counts as "wrong" physics, strictly speaking, but it is obsolete, more obsolete than a penny-farthing bicycle, and it will all have to be unlearned before there can be any hope of understanding modern (post-1908) relativity, including general relativity aka gravitation.

The book introduces Kirchhoff’s "laws" without hinting that there might be any limitations to their validity ... much less elucidating what the limitations actually are. This is a matter of some significance to premed students (among others), on rare occasions life-and- death significance, because hospitals have lots of problems with ground loops, i.e. with circuits that violate Kirchhoff’s laws. Some hospitals forbid people to carry cell phones ... not just to use them, but to even carry them ... because they are tired of the things messing up the heart monitors and other instrumentation. If there were more people who understood the physics of the situation this would be much less of a problem.

You’d think that by the time they got around to the 13th edition they would fix some of the most glaring errors.


I have not reviewed this book in any detail. I just mentioned a few examples that I found with a few minutes of effort.

Based on experience with other books of this size, I would be willing to bet that this book contains hundreds of errors, many of them far more serious than anything having to do with Lenz’s law.

Writing books is hard. I reckon producing a really good book would be comparable to producing a small Hollywood movie. The problem is, everybody including publishers and authors wildly underestimate how hard it is, so they try to get by with nowhere near enough resources, and the quality of the product suffers accordingly.

I consider this to be management malpractice on a grand scale.


Copyright © 2014 jsd