MIT circuits notes & more

Some nice slides & notes from MIT's intro electronics course. Might be good reference material for our upcoming mid-semester project.

Reference material / upcoming material

One quick thing, before you stop reading: we need to have another exam soon. We will postpone it until next week, even though I had nominally scheduled it for this coming Friday. Plenty of time, and I'd rather we get through a bit more material first.

Some time ago I wrote a short math guide for intro PH courses. You might find it useful, though it isn't as complete as I would like. Actually, you might find it more useful when you get to 300-level PH courses that use vector calculus fluently.

Also, I came across a great electronics text online from Texas Instruments geared specifically toward op-amps. We've covered enough material now that the 'Review' should make sense now, so if you want to do a little reading on what we're doing now, this is a good start. My own favorite reference is The Art of Electronics by Horowitz and Hill, which is in the Rogers library. Our coverage of transistors, signals, and op-amps has been based largely on their treatment. Great book if you can find a decently priced copy, highly recommended if you plan to continue fiddling with circuits.

For the next few classes, we'll continue our discussion of magnetism. Our focus is going to be calculating the magnetic field due to various distributions of currents and the effects of magnetic fields on moving charges and currents, without much regard to *why* moving charges create a magnetic field for the moment. We'll also cover permanent magnets a bit. Later, after we've gotten through induction and time-varying E and B fields, we'll return to the subject of why magnetic fields arise in the first place, which will require a crash-course in special relativity. For that, you might find my PH102 notes useful. Light on math by construction, but they cover special relativity, deriving B from E, and at least touch on most of the topics in PH126.

What we covered today / what comes next

Today, what I basically derived was the Drude model of conductivity (or from an alternate viewpoint, the complex dielectric function). Griffiths covers essentially the same material in Ch. 9, treating the problem from a dielectric-centric viewpoint. The Feynman Lectures (vol II) also does a great job of covering the same material, in much the same way that we started today (i.e., from harmonically-oscillating charges). I would suggest reading Feynman, then Griffiths if you are curious. Follow that with Jackson Ch. 7 (link below) if you're really excited.

Here are a couple links you might find useful, if you are interested in going through what we did today a less brutal pace:

• Summary of the Drude model
• Ch. 1 of Solymar & Walsh does an excellent intro job (awesome book,I have a copy)
• Jackson Ch. 7 is fairly readable (when compared to the bulk of the book ...)
• Feynman Lectures II.32 (must read; dielectric-centric)
• Brief Derivation (fast-paced, but good)

Anyway: now we know why metals are shiny, and insulators are mostly transparent.

This brings up a question: we have one more recitation (Fri) which will be devoted to the RFID project, and one more lecture (Mon). What do you want to hear for your last lecture in PH126?

Anything you want, within reason and physics-related (if tangentially), I'll do my best. Leave your suggestions in the comments.

Relativity

If you find relativity interesting, and you've had a bit of math, you'll probably find these lecture notes very nice. In fact, they've been turned into a book by Prof. Carroll, which has been well-received (it is what we use for our grad relativity course).

There is also a "non-nonsense" introduction to general relativity, the first bits of which should be familiar. Don't be scared by the tensors later on, the barrier is mostly the notation.

Anyway: good book, free preview online. Can't beat that.

Power

Ahem.

Do not try this at home

Wow. Relax and get some sleep before the exam.

Feynman lectures & videos

In case you missed it, this comment is worth a read, from the editor of the Feynman Lectures on Physics. Yay internet!

Also, you should really check out the video lectures by Feynman himself, made available to the public by a very generous gift from Bill Gates. These are lectures from 1964 at Cornell, and were not really available to anyone until Mr. Gates took it upon himself to make it possible. Many of the lectures tie in to the Feynman Lectures textbook, and are well worth checking out.

No matter how you feel about his software, the man has done physics a solid ...

Cube of charge

Two things:

1) The MIT course analogous to ours is 8.022. Open courseware is awesome.
2) Problem 4 on your homework is the same as Purcell problem 2.30.

Actually, most of your problems so far have been from the Purcell book, as it turns out, which is also favored for 8.022 at MIT during certain semesters. Looking through the 8.022 content on the open courseware site is highly recommended. Typically very thorough and lucid solutions.

Not all their content is on the open courseware site yet, but it can be found. try googling "purcell 2.30 MIT 8.022" and look at the first couple of links.

Restoring old moon footage

Fascinating stuff. Apparently, incredibly high-resolution image data of the moon (taken by an orbiter in 1966 to survey possible Apollo landing sites) has been sitting in a barn in California for about three decades.

Related presentation by a project team member.

MathWorld

It is the awesome. If you can't remember some bit of math, or need to pick up something new quickly, it should arguably be your first stop (the other argument being in favor of wikipedia, which in my opinion can be too terse).