Wednesday's class

Wednesday, we'll cover magnetism in a bit more depth. Specifically, we'll look at some tricks for how to solve for the field due to an arbitrarily-shaped wire with the Biot-Savart law. A good reference is this paper (you can only download the paper from on campus), which shows a cute trick for calculating the field from any wire whose geometry you can express in polar coordinates.

We'll also delve deeper into Ampere's law, and figure out how to find the field from solenoids and current sheets, which will let us derive some boundary conditions on the magnetic field at current sheets, similar to what we did for the electric field near sheets of charge.

Finally, we'll look at the most general equations we have for magnetostatics (i.e., only steady currents) and contrast the current situation to electrostatics.

Once we're done with the lecture part of class, we'll start in on the project for the rest of the semester: figuring out how to read RFID. There will be many sub-projects: coding, building circuitry, antenna design, and more. It will not be easy, but I think it will be a lot of fun, illustrate how one must be careful with this technology (morally speaking), and require all of you to pool your diverse expertise to work on a large project. Tomorrow, your task will be to figure out (1) what is RFID anyway, (2) what basic physics is involved in it, and (3) come up with more specific information-gathering missions and delegate them.

If all goes well, at the end of the semester you will know how to read my campus ID while it is still in my wallet. Of course, we'll have to be very careful about what we do with the knowledge we gain: knowing is one thing, but doing is another. There are rules.