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All entries for Thursday 12 May 2005

## May 12, 2005

### Plasma Physics

Those of you who were around in Wind Orchestra last term will have heard me comment on my Plasma physics lecture course quite frequently. Often those comments were a sort of tongue-in-cheek despair, and for good reason. Now the chickens are really coming home to roost. My exams start on Tuesday, but the dreaded Plasma is one of the last ones.

Having tried to revise the whole course, answer all the example problems, and attended the revision lecture, I've come to the conclusion that this course is simply impossible. The only question on the sheet that I can do is Question 2, since it involves plugging some numbers into some equations (hurrah!).

Why is this? Well, for this year only we have an external lecturer from the Joint European Torus in Culham come in to do the course (Dr Ken McClements – yes he is scottish, and believe me he knows a lot about plasmas, but the lectures were terrible). Thus this year it's completely different from previous years. This first of all makes the past papers irrelevant. The real problems are that a) the quantity of material is far too great, and b) the level is far too high.

Take point a). It's a 15 lecture course. Each lecture came with 8 pages of notes (filled to the brim I might add). This makes for 8×15 = 120 pages of notes. 120 pages for a 7.5 CAT module. Hmm! Anything in those notes could be examinable, and it's not worth anything more than say, Stellar Structures, where I have about 20 pages of handwritten notes.

And onto b)? Well, the notes are just full of derivations. It's ALL theory. Applications? Using the physics in any way? Forget it! It's deriving motion of particles using Lorentz Force balance equations for 5 or 6 different cases, then onto Derivation of fluid equations, then onto MHD equations, types of MHD equilibrium, MHD instabilities…(MHD = Magnetohydrodynamics. Sounds long and complicated but it just means "the movement of things in fluids in the presence of magnetic fields". All physics is like that).

None of these derivations are trivial either. Most run into pages, of multiple non-intuitive steps. I know I won't get much sympathy from the Mathematicians, who have to learn that sort of rubbish all the time, but the trouble in physics is that derivations aren't mathematically as rigorous. You get so a certain point and then use some trick, make some dodgy physical assumption, and carry on that way. So unless you know what trick to use, you're stumped!

The example questions are horrible too. They don't test you on things that are explicitly in the course. They take something that you touched on and try and get you to prove some interesting fact that you've never seen before. Worse, the problem answers don't actually show you how to do it. They just say things like "we use the fact that A is true, and write B. This hence leads to answer Z. How? Don't ask, it doesn't say.

It's now so bad that even trying to revise Plasma Physics any more makes me very depressed. So I've given up. It's only one of the 8 exams I have to take over the next 12 days. The other 7 are all worth just as much. Everyone I know left doing the course says the same – it's far too hard, so it's just not worth it.

Sorry, this has turned into a real rant I see. Ah well. Plasma Physics deserves it I'm afraid! Look at the notes if you don't believe me :-)