There will not be any further HW.

Given that next week is dead week and you have an exam on Friday, we'll call it quits at 8 homework sets. Christmas comes early this year ;-)

Exam 3

The coverage for exam 3 on Friday will be:

• magnetic fields (2 problems; Ch. 28.2-4, 6, 8-10; 29.2-6)
• motion of charges in magnetic fields
• fields due to current-carrying wires (Ampere, Biot-Savart)
• induction (2 problems; Ch. 30.2-8)
• motionally-induced voltage
• Faraday's law 
• ac circuits (1 problem; Ch. 31.2-9)
• filters
• impedance

Nothing on op-amps/transistors/comparators, Maxwell's equations, EM waves, or relativity for this exam, though some of that may show up on the final. Similar to the homework problems, but less involved. Out of the 5 problems, you will have to choose 3 to solve, so the odds are not bad. You'll have 50 minutes for the exam. I'll provide a basic formula sheet with everything you really need, and you can bring in one sheet of your own.

I'll try to provide some more details on Wednesday in class, but feel free to remind me or ask some questions. I will really try not to make it too difficult ...

New Spring courses

We have two brand-new never-before-offered courses this spring you might want to consider:

AY 155 - Life in the Universe     (Silverstone)

PH 482 / PHL 480 - Physics & Metaphysics   (LeClair / Hestevold)

Links go to course syllabi, let me know if you want any more information.

Course evaluations

It is that time again ... please remember to do your online course evaluations. I won't see them until well after final grades are due.

This course will be using an online system for collecting the end-of-semester Student Opinions of Instruction questionnaires.  Your response is very important and is used to assess curricular and instructional quality, as well as to identify opportunities for improvement.  The online system enables you to: 

• complete the questionnaire anytime, anywhere, at your own pace allowing for more thoughtful and constructive responses
• save and return later, as well as review and edit responses prior to submitting
• responses are confidential; only a summary of all student responses will be provided to your instructors and administrators.
• For more information about this process, go to http://oira.ua.edu/soi/soi_info.html.
• Beginning November 28, 2011, the Student Opinions of Instruction questionnaires will be available. You may access them as follows:
• Login to myBama and select the “Your opinions matter!” image on the Student tab.  Once in the system, you will see a list of courses you are being asked to evaluate.
• An invitation containing a link to login will be sent to your Crimson account.  Up to 3 reminders will be sent; reminders will only be sent to those who have not submitted all questionnaires for all courses.

HW8 hints

Problem 6 is a bit sneaky. Think about how the capacitance relates to the geometry of the capacitor (C ~ A/d), and how those distances are contracted. If you move toward the plates along the axis, the plate spacing is contracted, but area remains the same. If you move perpendicular to the axis, the spacing is the same, but what happens to the surface charge density?

As one hint, charge is invariant, and always the same no matter what relative motion there is.

As a stronger hint, I was about to post my notes on radiation, which starts out with the fields of moving charges ... 

For 7, note that F = qE = dp/dt, with momentum p=(gamma)mv. Then

dp/dt = (gamma) m dv/dt + mv d(gamma)/dt

With the definition of gamma, grind through the derivatives and it should work out.

I'm going to run through #6 and 7 tomorrow in class in any event, just to make sure you know how to get started.

Final project parts have mostly arrived

Most of your stuff is in, I think we're only waiting on the multiplying chip, which should arrive on Tuesday. Here are some details about what I've got ...

Relativity notes

We're covering relativity right now, and obviously it is not in your book. I will be following my own notes here. See Ch. 1 for relativity, treat it as the missing chapter in your textbook that really should have been included.

You should also check out the chapter on magnetism (Ch. 7, iirc), it contains a simplified derivation of the magnetic field from the electric field in a moving reference frame.

Final project parts

Having not heard much yet, I went ahead and ordered a few things for the final projects that I guessed you would probably need or could use:

• 160 assorted LEDs
• 3 of these 9x14 LED blocks (red, green, blue)
• 3 continuous rotation motors
• a multiplying chip for constructing the theremin
• 20 125kHz EM41000 RFID tags

Most of this stuff should arrive by Monday, all of it should be here by Wednesday. We may need some other parts yet (which you should specify ...), but this should be enough to get us started.

Today:

a reminder that you will have a lab day today, no lecture. You can show up at the lab directly at 11:00. I have an appointment in Birmingham this morning, and will probably not make it back at all, though I will try to catch the end of the class. Your undergrad assistant will be there, and I arranged to have the room opened at 11:00.

Your main goals today, if nothing else, are (1) better define your final project, getting down to some of the details of what you are going to do, (2) come up with a list of (at least preliminary) items you will need me to procure.

In particular, if you need me to buy stuff (like LEDs, RFID cards, etc) I need to know that ASAP so I can have it by next week.

HW8 is out

Covers ac circuits mostly, with a couple of relativity questions thrown in (we'll get to that next week). Due next Friday.

Should have HW7 solutions out this evening ...

Next HW

HW8 will probably come out Thursday, covering mostly ac circuits, and it will not be due until something like next Friday. I got a little delayed making it up today ... it should be a bit shorter than the last couple.

Remaining Schedule

We're down to about a month to go now, and here's what I have planned lecture-wise: