Grades

I have just finished grading the final exams, and the average was about 82%. I was pretty happy with how it came out, and most of you didn't end up changing your grade going into the final exam by very much. I should have your grades posted Monday evening some time, and will try to email each of you a grade breakdown as well. 

Final project videos

All the final projects finished up nicely, and we have video and code for all of them. So, in case you want to try them out, here is some information:

4 bit maze [Daniel Jenkins, Andrew Wagner]:

Mr. Jenkins and Mr. Wager implemented the Arduino four bit maze found here, and explain their project in this video.

d-pad/joystick controlled Etch-a-Sketch [Coston Rowe, Andrew Hicks, David Thompson]:

Mr. Rowe, Mr. Hicks, and Mr. Thompson used Parallax servo motors and a homemade joystick/d-pad to remotely draw on an etch-a-sketch. Their Arduino code is here, and they describe their work in this video.

Daft punk helmet [Jacob Moxley, Cameron Darling]:

Mr. Moxley and Mr. Darliny used an Arduino Uno and the LoLShield they assembled to create a Daft Punk-inspired helmet with scrolling messages. Their code was based on cibomahto’s LoLShield library, with some modifications to fix lower-case letter display and implement sprite-style graphics. They describe their work in this video.

RFID tunes [Ali Cortez, Max Peeples]:

Mr. Cortez and Mr. Peeples implemented a tune generator based on reading RFID cards that encode pitches, notes, rests, etc. Their code and all project details are here, and they describe their work in this video.

“Incredimen” pseudo-Theremin [David Gillespie, Derek Brazzell]

Finally, Mr. Gillespie and Mr. Brazzel made a pseudo-Theremin. The main differences from a traditional Theremin are the use of lower frequency oscillators (~80kHz) to make things easier, and using a op-amp simple summing circuit for multiplexing rather than a more complicated mixer. The use of lower frequencies does impact the sensitivity, but it still works great and sounds very, very weird. They describe their work in this video, which apparently they spent quite a bit of time on!

If you want more project details, you can contact me and I'll either tell you what I know or put you in touch with the students who did the project.

Final exam hints

The final exam is really difficult. My wife asked me if it was difficult because you all hadn't studied enough or something, and my reply was "no, they have studied, it is just really difficult." Then I decided I should probably help get you started a little bit ...

Even with massive hints, some of them are still very hard (or messy, or both). They are more open-ended problems than you are probably used to, requiring approximations or assumptions that you have to come up with on your own to generate reasonable solutions. With one exception, not the sort of problems where you just identify formulas or set up an integral or two. If there is a lesson here, I guess it is that realistic problems are messy and difficult, and half the time you don't even know where to start. The trick is to figure out how to make it look approximately like one of the nice tidy textbook problems, without sacrificing too much in the way of accuracy or realism.

Anyway: here are the massive hints I spoke of. I also corrected a typo in number 4 - it should be "b/a" in the log, not "a/b".

Your final exam

Here you go. Feel free to ask questions about the problems if something seems unclear, or you don't know how to get started. I'll clarify what I can without giving away too much ...

Dell laptop cord left in lab

I found a stray Dell laptop power cord in the lab after class today. I'll bring it to the main office (206 Gallalee), if it is yours you can drop by to claim it from 9-12, 1-4:45 any weekday.

Continuing your projects

Just a thought: if any of you need PH elective credit, and would like to continue to refine and complexify your final projects (or something else), I'd be happy to work with you next semester via an independent study course. If this sounds like something interesting, let me know and we can talk about the details.

Final projects and "report"

Well, everyone's project basically works. Most of you have a little polishing to do, but the basic idea worked out for everyone, and you managed to build some pretty cool stuff. It would be a shame if this information were lost, right?

Keeping that in mind, and the fact that nothing can really be deleted from the internet, I've decided to change the final reporting requirements. In your favor, as it were. Rather than writing a final report at this late date, I want you all to make short videos describing your project, along with a demonstration of how it works. There are no real restrictions, just a few guidelines & suggestions:

• You don't have to be on camera yourselves, just your project. You do have to speak though.
• A few minutes is enough, if you can describe the project well enough
• You should briefly describe the point of the project, showing diagrams or schematics as necessary (say, on the blackboard or a sheet of paper) so it is clear how you made it work
• Describe the hardware and code required to make it work, in brief. Include links with the video to make this easier (see below).
• End with a live demo of the project, showing its basic functionality, operation, and major components
• Upload to YouTube or your preferred time sink
• If you made heavy use of particular web pages (e.g., schematics, code, etc), send me those links.
• The video + links should be enough for a reasonably proficient tinkerer to reproduce your project.
• Do plan a short script or sketch of what you want to do for your video, it will not go well if you just start shooting and rambling at the camera :-)

I'll post links to the videos here, along with files of any schematics/code you think is non-obvious. The basic idea is that should someone like yourselves search for a similar project, they'll find your video and any interesting supplemental information required to make it work. Maybe then they will have an easier time doing it themselves, or at least be inspired to try it out, having seen it is possible. Many of you came up with your projects this way, so you'll be paying it forward a bit.

During Wednesday & Friday's classes, I'll bring in my camera, phone, and laptop (all of which take video), or you can use your own phones/laptops/etc. There should be enough time during those two class periods for most of you to complete your short videos, or we can work out another time for you to come in and do it outside of class if you like. For that matter, if your project is portable, you can do it in your dorm room.

So, all you really need to do for your projects at this point is (1) polish as you see fit, (2) take a video, (3) turn in any code/schematics/links/etc to include as supplemental information with the video.

Grading will count one lab report grade each for: (1) video quality/clarity/etc, (2) functionality of the project (how well it worked), (3) overall polish of the completed project (hardware & code), (4) creativity in coming up with and implementing the project. That means the final project is just under half your lab grade, which is itself 15% of your overall grade. It is a group grade, each team member gets the same grade for the final project.

More details and discussion in Wednesday's class.

Notes on EM waves, radiation, etc

Here are some notes on radiation, EM waves in conductors and insulators, etc - the stuff we've been covering the last several lectures. They are rather long, and incomplete in places ... but they do cover some interesting things I didn't quite get time to go over in lecture.

The first part is deriving the radiated power by accelerating charges, and applying that to several systems (oscillating charges, circular motion, etc.). The second part is deriving the blackbody radiation, which we did not cover (you'll see this in PH253). The last part is EM waves in solids, complex conductivity and dielectric functions derived from a model of oscillating charges. An appendix shows how to derive B from E in a moving reference frame.

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:

HW7 miscellanea

Since we don't have class on Friday, I thought I'd post some HW hints. Keep in mind that the HW is due Mon 31 Oct at midnight, so we still have Monday's class to discuss the problems, i.e., I have not necessarily ruined your long weekend :-)

HW6 solutions

Here are some proposed solutions to HW6. The circuit construction questions have many possible solutions, so if yours does not look like mine, don't worry too much.

HW7 out, due on halloween, appropriately.

I don't think you'll like it at first, but we will do at least two of the hardest problems in class. Keep in mind that halloween is the Monday following Fall break.

HW 4&5 solutions

Long overdue, but HW 4&5 now have solutions. Have a look, this stuff will come back again, if nothing else on the final exam. Some of it before then.

HW6 is a beast in fact.

If you put it off until the last minute (i.e., right now) and tried to do it in one night, it isn't going to go well. You may want to ask for an extension, as it is likely to be given. This is important stuff, I'd rather you understand it a bit late than not at all. 

Clarification of HW6.1

One of you asked:

Dr. LeClair, I was curious about number one. The problem seems pretty straight forward, I would hesitate based on its straight forward reading even calling it a problem but I wanted to know more what you wanted to know from this problem and what you expected to see in our answers. Do you want us to do this purely on research and give you an answer that goes into detail on what we find, since you said, "Can you suggest ways in which two short coils or current rings might be arranged to achieve good uniformity over a limited region?" Or would you like to see a derivation that leads us to the final conclusion? My point being that I only found out what the answer is through researching and I want to know whether you would like to see me spit out a derivation to show that I know what I found is true, or would you like me to just explain where B is most uniform and why that is the case?

I guess to be really specific, a uniform field could be defined by stipulating that the spatial derivatives of the field along the axial direction vanish in the middle. Say z is the direction along the coils' axes, then dB/dz=0 and d²B/dz² = 0 halfway between the two for a very uniform field.

There is one special spacing of the coils that makes that true. So, call the distance between them (say) 2b, find the field at an arbitrary point z between them. Find the first two derivatives, and set both equal to zero at z=b. This will give you a value for b in terms of the coil radius R. Look at http://en.wikipedia.org/wiki/Helmholtz_coil for the actual construction and spacing.

So I guess ideally what I'd like to see is this - a condition that defines uniform field (derivatives zero) and a calculation that specifically finds the spacing for which it is fulfilled. I would probably give mostly full credit for researching the answer and providing a solution, but without a solid reason (i.e., derivation), it wouldn't be the full story or full credit.

Mid-semester project: fan rpm sensor

Wednesday, we'll start a mid-semester project: building an rpm sensor for a fan. Here is a rough description of the project and your expected deliverables. We'll talk about it more in class tomorrow, but it will be very free-form: I'll give you a problem to solve, a few suggestions, and see what you come up with (along with guidance along the way of course).

If you think about the last few labs we've done, and pay attention in tomorrow's lecture, a decent solution should present itself. You've already built all of the circuitry required as previous projects, the trick will be combining it all together. Similarly, you've already written the code you need (counting pulses), in principle. I have already done the project in one way, so it is workable using what we've studied.

I expect we will spend 3-4 lab sessions on this, but we'll go as long as it takes. Once this is done, we'll start longer projects of your own choosing, something that will take most of the rest of the semester to build up and fine-tune. (Maybe something like this?) Details on that to follow in a week or so ...

Condensor microphone

Today in class we talked about how one can build a microphone. Here are instructions on how to actually build a condensor microphone out of 'household' items. Basically like we said - one fixed electrode, one flexible, the sound (pressure variations) change the capacitance and generate an electrical analogue of a pressure wave (sound). 

Midterm grades

I'm about to post midterm grades. A couple of things:

• I am erring on the side of optimism with regards to your probable grade.
• The grades include HW1-4, Exams 1-2, and a lab grade of 100% for everyone since we haven't had any real reports due yet. (That changes Wednesday, however, you will have reports to do soon now that you know how to build stuff.)
• I am dropping your lowest homework. See first point.
• Some of you are missing homework sets, which is sort of a big deal with only 2 exams in. If your grade seems lower than expected, that may be why.
• If your grade seems wildly out of order, let me know - I can change things up through Wednesday.
• One of you missed the second exam. This is an even larger deal, and you should probably talk to me. It is not catastrophic, but not great either.

On Wednesday, I will show each of you your grade breakdowns, including what HW sets I might be missing from you, to make sure everything seems to be in order.

HW6 / Pulse height discriminator

On the homework, you're supposed to design me a pulse height discriminator, a circuit that detects when its input has gone above a certain threshold level. The simplest way one can do it is probably this, a single diode and capacitor. This circuit isn't great, though, since for one the threshold voltage is basically limited to the diode's forward voltage drop. That particular problem can be cured, but generally speaking, it is just not very flexible.

A much more elegant solution, like we talked about in class today, is to use a comparator. They're cheap, simple, and plentiful. This way you can make zero-crossing detectors (when does a signal change sign?) or peak detectors. The LM311 datasheet has some nice examples - look at the zero-crossing detector, and positive/negative peak detectors [pulse-height discriminator]. These circuits do basically what we want. [The LM110 in those circuits is just a 'follower' like we talked about today. All it does is makes its output the same as its input, so for the purposes of understanding the circuits, ignore it.]

So, why is this a homework problem? The rpm readout circuit you'll begin building next week will rely critically on this sort of circuit, so by the time you have to build it, you'll already have a working design ready. Details on that project to follow this weekend, we'll begin on Monday.

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.

Tomorrow / HW6

I think we should put off HW6 until this coming Wednesday (19 Oct), I don't feel like we've covered magnetism well enough yet. So, no HW due tomorrow.

As a result, tomorrow we'll do a little new material (Ampere's law, current loops & solenoids) and go over a few of the HW problems.

Why I was dressed up yesterday.

http://uanews.ua.edu/2011/10/teaching-award-winners-honored-at-ua-3/

Exam 2 post-mortem

I will have the exams graded by Wednesday's class. You can find the exam and partial solutions here. I think we'll probably spend a good deal of that class period going over the exam problems and common misconceptions. It was a hard exam, no question, and we are not in a rush to move on, so we can afford to spend a little time thinking about it.

For now, don't freak out. I'm not going to fail any of you based on a quick glance of the exams, and the partial credit will be generous. It is simply much easier for me to gauge your understanding with very hard problems than very easy ones - if you got everything right, I'd have no way of seeing the limits of what you've learned so far. So, focus on learning something from the exam for now, the grades will be better than you think.

Exam 2

You can bring in one sheet of paper with whatever you want on it to the exam, and I will provide another sheet with all the core formulas, constants, etc. Don't bother memorizing anything.

Exam 2

The coverage for exam 2 on Monday will be:

• potential due to charge distributions
• potential energy of charge distributions (e.g., crystals)
• dc circuits (batteries, resistors; multi-loop circuits)
• capacitors and RC circuits

Nothing on magnetism. I'll give you a formula sheet, no need to memorize anything. No problems involving transistors or op-amps, and no magnetism. Similar to the homework problems, but less involved ("easier") ... more details to follow over the weekend.

The exam will be designed to take an hour, but I'll give you 1hr50m.

HW6 is out

I know you're excited.

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.

Tomorrow's lecture/lab

Having mastered the blinkenlight, tomorrow you'll build an amplifier/filter out of op-amps. Check it out.

We'll spend a little bit of the lecture-type period with me introducing new material, but the bulk of it on working out and discussing homework problems.

HW5 / today's lab

Since I have delayed our discussion of magnetism, HW5 is delayed from this Friday (30 Sept) until next Wednesday (5 Oct).

In today's lab (and the last part of lecture) we investigated a comparator-based relaxation oscillator. You will probably want to read over how it works a few times to make sure you get your head around it - it is a bit subtle. The important thing is not so much that the circuit oscillates, or that we can make a light blink on and off (we could already do that), it is the general idea of feedback. That is, the circuit is configured in such a way that past output affects present operation, and this allows us to do exceedingly clever things. We'll see this more and more when we discuss op-amps next week. 

Wednesday: more circuits

Though we are a little behind where I imagined we would be, we are ahead of where we have to be, so we'll spend the rest of the week learning how to build and analyze more complex circuits. We're almost far enough that I can let you design your own projects ...

Wednesday, we'll re-hash what we know of transistors and learn how to build a basic amplifier (on paper, for now) [slides I'll use]. We'll then focus our attention on comparators, a simple-yet-powerful device that compares two input voltages. This will serve as an introduction to feedback and basic logic circuits, which will let us build all sorts of neat things.  Such as a relaxation oscillator, which you will actually build in the lab [circuit]. We'll use it to make an LED blink periodically without any code at all. So far as circuits go, we only need to know about a few more components (inductors and op-amps primarily) before I'll just start turning you loose on projects.

Next week, we'll move on to magnetism and magnetic fields, which means back to more abstract things for a while. Lab-wise, next week we'll try to learn a bit more about coding for the Arduino. Once you have a bit of software knowledge to go with your hardware knowledge, we can do very neat things. You should start looking at some possible projects.

HW5 is out

Here it is. I think it is a bit shorter than average, but I am probably not the best one to judge.

For tomorrow's lab, you will be designing and building a variable current source out of an npn transistor, a few resistors, and a potentiometer. You will verify that it operates as expected by checking its performance for various load resistances at fixed supply voltage, and then by verifying for a fixed load its behavior as a function of supply voltage. You will probably need to make use of the notes.

Friday's class

Friday's class will be mostly devoted to going over homework problems. I think most of them should be able to get a decent start on at least, but we'll go over most of the problems in class (at least setting them up).

If there is time remaining, we'll look at a few more transistor circuits to figure out how they work. 

Wednesday's class & lab

Last time, we learned basically all we needed to know for analysis of steady-state dc circuits. Today we will put some of the rules we came up with into practice and learn a few more tricks for circuit analysis. We'll also add a few more elements to our toolkit - in particular, diodes and transistors - to go with the resistors, voltage & current sources we already know.

For the lab, you will be constructing one of two transistor-based circuits: an automatic night light, and a burglar alarm that senses when a door opens. For the former you will use a photoresistor or phototransistor as a light sensor, and for the latter you will use a Reed switch and a magnet as a motion sensor. Both circuits are derived from a very basic transistor-based current source, which we will analyze in class.

I've written some notes on transistor circuits, since you will not find them in your textbook. We will not go into great depth, just enough to learn how to make some neat and functional circuits. I you are an EE major, this will either be review or a preview ...

HW3 solutions

Here you are.

HW4 is out

HW4 is out, consisting mostly of problems on resistance and simple circuits. 

Random HW3 hints

Massive hints for your imminent HW set:

Wednesday & Friday

Wednesday, we will probably have limited time in the lab in order to get through the next material. It will be easier to explain with a longer block of time at my disposal, so we'll mostly do lecture on Wednesday and devote Friday entirely to lab work [i.e., no lecture on Friday, but there will be lab work to turn in].

We've slipped a bit from the schedule I posted at the start of the semester (somewhat anticipated), I'll be revising that soon to reflect current reality. Along those lines: let's make HW3 due Thursday at midnight, with HW4 coming out then.

Wednesday, we're going to finish off our discussion of potential by figuring out how to find the energy required to assemble solid distributions of charge - for example, how much energy does it cost to assemble a uniform sphere of charge? After that, we'll discuss the peculiarities of charged conductors, which will set us up for discussing current and the last bits we'll need to start circuit analysis. As an aside, we'll learn a neat problem solving trick, the method of images. It is really a general technique for solving differential equations, which amounts to 'make the problem look like something else, and write down the answer.'

Friday will be an 'inquiry-based' laboratory session, a fancy way of saying that I'm going to pose a problem for you to solve, and see what you can figure out. The general idea is to let you fiddle around with circuits for a while and learn how to make things work, so when we finally know how to analyze & design circuits mathematically, you'll already know how to turn ideas into reality. Or, more simply: paper circuits and equations don't do a thing, we want to build things.

Monday's lab & lecture

Monday, we will continue our discussion of electric potential. Now that we know the generalities, we can get down to business and figure out how electric potential will let us solve problems more easily, just as potential energy did in mechanics. As a bonus, we can derive a method to analyze electric circuits in a very general way. As disjointed as things may seem so far, it will all come together shortly, and your patience will be rewarded.

The lab for Monday will consist of a few simple circuits and measurements to show you how to apply electric potential concepts, and make a little sense of the projects you've done so far. If you have time before class, have a look at the procedure.

Also, Monday I will give you back graded HW2 and your exam 1 scores. None of you has anything to worry about, unless you've been skipping the HW you have an A or a B so far.

Exam 1

EDIT: I probably cannot stress enough that I mean this week.

Just under half of you have scheduled your oral exam so far. If you haven't requested a time yet, you should do it soon ... Here are the times left:

Wed: 2:30-4pm, 5-6:30ish pm
Thurs: pretty well tied up in an all-day meeting.
Fri: 10-10:45, 12:30-1:45, 4-5, 5:30-6, after 6:30 if you really want to

It will not take more than 15-20min for the oral exam. You can use your book for reference (though if you thumb through it too long I may look askance at you). The topics are, by section in the book,

22.2 Electric fields
22.4-7 fields of various charge distributions
22.9 dipoles in electric fields
23.4 Gauss' law
23.7-9 Gauss in various situations

Nothing we'll cover tomorrow (Wed) is on the exam, and nothing from our lab sessions. Additionally, simplified versions of HW problems are fair game. And I do mean simplified - there won't be any complicated integrals to work out. Mainly, you will have to set up the problems and demonstrate to me that you know what you're doing more than actually doing all the calculations in detail. For example, setting up the integral to find the field of a line charge, but not having to perform the integral.

I will have a set of 8-10 problems, all of essentially equal difficulty, and each of you will have to demonstrate knowledge of two of them for me. If you get really stuck at any point, I'll help you along in the problem (though at the cost of a few points).

I'm fairly certain most (all?) of you have not had an oral exam before, but it will be relatively painless, and most of you will do very well. If you understand the material so far and the homework solutions, you'll be fine. Don't get lost in mathematical detail when studying, focus on what is going on in the problems and how to set them up.

HW3 out, HW2 solutions

Here are HW2 solutions. HW3 is now out as well, due Monday 12 Sept.

HW2 number 8

For question 8, you will need to sum an infinite series. It is in fact a very famous and neat little result, which you can find here.

HW2 / today

This afternoon, from 2pm onward, I'll be in or around my Bevill office (room 2050) if you have homework questions. You can also email/text me if you like.

Some of the problems on HW2 are well known (i.e., you could potentially google solutions or hints), some I have asked before in either PH106 or PH126. Just throwing that out there.

Lastly, in general if a HW problem suggests a particular method of solution, but you think you have a better way to get the same result, you can use your own method if you like. For instance, on #2 of HW2, you might decide it is just easier to superimpose the fields of two lines an a semicircle, since the field from those objects are well-known results, rather than setting up the problem as suggested. In general, any consistent method is fine, solutions by any means necessary. This means writing code or numerical solutions are fair game in general [but you should turn in the code with the rest of your HW].

Exam 1

As I mentioned in class today, we'll do the first exam as an oral question session. It will take only 15-20 minutes. The format will be more or less that I pose two problems to you, and you discuss them and work them out on the board in my office. Before the examinations start, I will give a list of topics that are 'fair game' and some example problems. They will not be as hard as the homework problems, certainly, more at the level of example problems in the textbook. You will be allowed to use your textbook for reference.

Each of you will need to schedule a 20 minute block with me next week Wednesday or Friday to make this happen. (If this is totally impossible, I can do a couple on Thursday as well.) Here are my free times on Wed and Fri next week:

Wed 7 Sept: 1pm-6pm
Fri 9 Sept: 12-3pm, 4-6pm

When you get a chance, send me an email with a proposed 20 minute block in those windows and I'll let you know if it is taken already. If you cannot make any times within these blocks, let me know your free times on Wed, Thurs, or Fri and we'll see what we can work out.

More details on the exam itself this weekend ...

Today's lab

Today, we'll figure out how to read the state of switches.

HW2 / HW1 solutions

HW2 is out, due this coming Friday (not Wednesday, as implied by the calendar).

HW1 solutions are also out.

HW2

HW2 will come out some time today Sunday ... due this coming Friday.

Notes on electric forces and fields

My notes for the non-calculus class (PH102) may be handy from time to time. The next several day's material corresponds to Ch. 2-3 in the notes.

(warning, ~23Mb PDF file)

Survey responses

Based on the survey responses so far (after filtering out the ones from random internet hobos filling it out), pretty much everyone has more than enough math background for what we'll need to do. I will stick to the level implied by the math prerequisites for any required work, but in lectures I will show you a few extra things, just because it will help later on, and it will be really cool. Anyway: don't freak out too much about the math, I will teach/remind you what we need as it comes up.

HW1

By the way, I should mention that professors in general have a habit of recycling problems that they like. Maybe from the same course, maybe from a similar one ... but if it were me, I would try googling key phrases plus the professor's name. That, and just checking last year's problem sets.

I won't reuse problems a lot, but given that I (a) assigned homework on the first day, and (b) made it due on the second day, I thought I should give you a fighting chance.

Friday's class

Friday, we'll be starting to discuss electric forces and fields. We'll skip most of the beginning of chapter 21 in your text, since it is fairly descriptive stuff you can easily read about, and dive right in to calculating electric forces. This would be the last few sections of Ch. 21, and the beginning of Ch. 22. I'll go over some questions on the HW set as well.

If you're having trouble remembering some of the vector manipulation, I did write a short math guide some time ago (and never quite finished, but close). Hopefully the quick tour of vectors on Wednesday didn't scare too many of you away ... we will start out slowly and work our way up to the harder things.

For Monday, you should have already read Ch. 21 and 22 (or skimmed them at least, let's be realistic here).

Today's slides

Here are the slides I used today [7Mb PDF], and a bunch I didn't use yet. Course information, contact info, and the vector stuff I talked about.

A quick survey

You all have a pretty diverse background, and I want to make sure that I'm not getting you in over your heads. It would be helpful for planning purposes if I knew a little about your math, programming, and electronics experience. Can you answer the following (very short!) survey?

The survey is totally anonymous, and the results will not be seen by anyone but me. It is really just to get a grasp of the baseline skills you're coming in with so I can tailor course topics (and especially the labs) to what most of you are comfortable with. Please answer as honestly as possible to make this as useful as possible to me; if you really don't feel like you understand one of the topics, don't select it (even if you think you're supposed to understand it).

The survey is here if you wouldn't mind ...

[If you're not in the class, and just saw this on Twitter/Facebook/etc, please answer "no" to the last question.]

HW1

Classes haven't yet started, but I already have your first homework set ready to go ...

Find it here, due Fri 26 Aug before midnight. I know that only gives you about 3 days, but it is very short. There are only four problems, and three of them are just math review. Only the fourth relates to material we'll cover in Wednesday's lecture (or see Ch. 21 in your text).

Anyway: I'll field any questions you might have about them in Friday's class.

Half-serious assignment: get yourselves on Google+ if at all possible. I think the 'hangouts' feature would be nice for office hours, and may try it. I have invites.

First lab

Tomorrow, we'll do our first lab: an introduction to the Arduino microcontrollers we'll be using for the rest of the semester. Here is a writeup of the background information you'll need - don't worry if it doesn't make much sense at first, it really won't until you just start doing the experiments.

Fall 2011 syllabus & schedule

Here you can find all the gory course details (grading, policies, etc)
Here you can find a detailed schedule, assignment due dates, required and suggested reading, etc.

My office hours this semester will be:

MW 1-2 in Gallalee 323

F 12-2 in Gallalee 323

TuTh 1-3 in Bevill 2050