IB thermodynamics: Course philosophy

No formal derivations, no handouts!

In the textbook you can find formal derivations and further examples, and ways of thinking about physics. What is the sense of my copying that onto the blackboard for you to copy it into your notebooks and then memorize them for use on an exam?

Only rarely will I give a handout, when we discuss formal material that is not in the excellent textbook: C. J. Adkins, Introduction to Thermal Physics (CUP, 1987). Most college libraries have at least one copy, and are all getting one photocopy. The Cavendish library has a copy on reserve at the circulation desk. And CUP says that they will do a digital reprinting soon, but no in time for this year's lecture course. Let me know if there are still book shortages.

Learn by speaking

If I won't do derivations in lecture, what will we do? Why bother attending? Because we will speak physics. The area of knowledge I learnt most thoroughly is my native language. I know it more intuitively than I know any other language, than I know how to ride a cycle, or than I know how to do physics. It is probably the same for you. How did you learn your native language? Probably not by going to lectures where the teacher described the rules for making correct sentences. I learnt English by speaking it: as a baby, by desperately wanting to communicate and trying anything that worked. So in lecture I hope to introduce enough interesting uses of thermodynamics that you will want to speak physics, and thereby learn physics.

Example sheets

There will be three sheets, roughly one for each week. The department conventions say that I can assign two problems per lecture. I hope not to overload you, so that you have time to think and wonder about thermodynamics as you walk around Cambridge.

I plan to give you my solutions along with the sheets, although lack of sleep may mean that I get a day or two late with the solutions (I am lecturing four courses this term). The solutions are for supervisors and for you, the students. Too often supervision turns into checking long derivations, when you could check your own work if you had solutions and then could spend the supervision discussion confusions or extending the problems.

My solutions will not always be right, although I'll try, and you may find more elegant ones. Your corrections and suggestions are very welcome!

Look at the solutions only after you do the problems or are terribly stuck. However, I cannot stop you from copying the solutions and turning them in as your supervision work. You will not learn much thermodynamics, but I am not your jailer. One proposal is that I give numerical answers or single-equation answers to the problems, as well as my longer solutions. That way you can get hints easily and feel less tempted to look at the answers before you have struggled with the problem. I'll try that with the remaining sheets.


Approximate answers are more useful than exact answers (except in conservation problems...). Approximate answers are mathematically simple, so mathematics does not obscure physics. The world is messy, and if you want to apply physics to the world around you, you need to approximate. Every example sheet and every lecture will give you practice with approximation.


This university is built upon exams and this country uses them as a fair means of damning many people to hell and sending a few to heaven. Exams thereby cause a lot of misery. Think how you feel if you do badly on an exam. You might doubt your abilities; you might fear that your future has been ruined. Neither feeling will help you learn.

Furthermore, exams encourage you to learn an idea because it is on the exam. But the ideas in this course are beautiful and lots of fun. I want you to learn them because of those reasons, not because they will be on the exam.

Exams can also make you dislike a subject. Alfie Kohn, an American writer on education, describes this pattern:

There are at least 70 studies showing that extrinsic motivators including A's, sometimes praise, and other rewards are not merely ineffective over the long haul but counterproductive with respect to the things that concern us most: desire to learn, commitment to good values, and so on. Another group of studies shows that when people are offered a reward for doing a task that involves some degree of problem solving or creativity or for doing it well they will tend to do lower quality work than those offered no reward. [My emphasis. From this interview about his book Punished by Rewards. See www.alfiekohn.org.]

Although final responsibility for the exam rests with the examiners, I will make the IB thermodynamics problems on the exam reflect what you learn from lectures and the example sheets and the examiners will vet the questions. The examiners have already written to me asking for my questions and they are very cooperative and friendly.

The fascinating history of Cambridge exams, and the Mathematical Tripos, is told by Andrew Warwick in his recent book, Masters of Theory: Cambridge and the Rise of Mathematical Physics (University of Chicago Press, 2003).

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