HW 2 results

Well, the average was about 83%, with a standard deviation of about 10%. Here it is by question, plotted as the fraction of full points for each question:

If you are in to the last minute exam-cramming, you might want to look at the solutions for numbers 3 and 7. EDIT: I meant, look at those before the final, they will not show up on today's exam.

By the way: your homework 2 grades are now entered in the online grading system. When you get your papers back, be sure to make sure your total points add up correctly.

Office Hours Thursday

After class, I have nothing concrete planned until the exam at 3:30.

Feel free to drop by Bevill 228 any time between 12:30 and 2:45 tomorrow for last minute questions, or grab me after class.

Sudden change of plans ...

I think we need to take a breather. You all seem almost as tired and jagged as I am ;-)

Tomorrow, rather than covering the lenses material as planned, we will be reviewing for the exam. I think right now you would benefit more from solidifying the material we already covered, rather than moving relentlessly forward. We'll pick up optics again on Friday.

So here's the plan for Thursday ... about 9 hours from now: I'll review briefly the material relevant to the exam. I will also bring some exam-like problems to solve and work on the board. You'll come with questions, and problems you want to see a solution to. Anything is fair game ... so long as it is related at least tangentially to the exam.

I had more or less built one extra day into the schedule from the beginning, just in case, for things like this.

I suppose this means that if you think you are ready to just completely rock the exam, tomorrow could be a waste of time. Probably, though, in my heavily sleep-deprived state, I will let some important hint about the exam slip. One never knows.

Today's lab ...

... has two parts. One, and Two.

Pretty straightforward, maybe 90 minutes combined at best.

Exam II / Homework 4

The exam on Thursday (3:30pm, in the lab room) will consist entirely of problems, no multiple choice. It will be broken up into four sections. In each section, there will be 4 problems, you must pick 2 to solve in each section. Thus, you solve a total of 8 problems, and you will have about 2.5 hours to do it in. I expect you will need more like 1.5-2 hours.

The sections are:

1. dc Circuits (mostly Kirchhoff's rules) - solve 2 out of 4
2. Magnetism - solve 2 out of 4
3. Induction - solve 2 out of 4
4. ac Circuits - solve 2 out of 4

All problems are equal weight, you pick the two in each section you think you have the best shot at. There will be heavy partial credit - try to show as much work as possible.

There is nothing on EM waves or light included. You can bring in one formula sheet (8.5x11 in, front and back) and a calculator; the exam will include the minimal set of formulas you will need.

I suggest (strongly) studying last semester's homework and exam questions, and additionally the example problems in the book/notes. There will be a good number of problems that will look familiar. Also, it is crucial you don't get stuck on anything. Probably most of you will not quite finish 8 problems, maybe 7. Pick your problems carefully, and start with the ones you are most confident with. This will be an exercise in time management as much as anything.

All that being said, it will be a fair exam, no tricks. Just fair warning.

Well: there is also one more homework set to do, it is due on the last day of class. Here's how the last one will work: you solve all of the problems you didn't attempt on the exam as homework problems. Thus, you will also have 8 problems for homework 4. Probably, you will find that your classmates solved different problems on the exam than you did, and a group of 4 or 5 of you should be able to cover all of them ...

Partial HW3 solutions ...

... are out. By the time you read this, I will have stayed up late and finished another problem or two. Most likely, the solutions will be substantially complete by mid-afternoon tomorrow.

UPDATE: there are now solutions to every problem in fact, though for two problems I have just given links to existing solutions online. I hope to have my own version of those soon.

How to see your grades online

So, I have a system set up so you can log in and see your grades. Probably, I should have mentioned this earlier ...

Anyway, go here: http://faculty.mint.ua.edu/~pleclair/moodle/

Click on "General Physics II / Summer 2008."

Then, to log in to the system:

• your username is the first letter of your first name + your last name.

Thus, if your name is "Jebediah Dingus" your username is "jdingus" ...

• your password is the last four digits of your CWID. You can change the password if you like after logging in.

Once you have logged in successfully, you should be at the main ph102 course page. There are a great number of things on this page, most of them are not useful. This is a new (and free) online course system I'm test-driving, so most things are just placeholders.

From this page, you can access your grades. You should see a link for "Grades" on the left-hand side of the page, about halfway down, under "Administration." For that matter, you can change your profile, create a little blog or discussion board, or all sorts of other things.

This is the system I'm planning to start using next semester ... and frankly, I'm using you to help me test things out. The system is perfectly secure - no one else will be able to see your grades or other information - it is the functionality and user interface I'm testing.

So: any feedback you have on this system is helpful. Let me know if it works ...

Online matrix calculator

Handy. Solves systems of equations and calculates determinants, among many other things.

By the way ...

I was just reading an interesting and very well thought out discussion that touched on professors assigning their own textbooks for a class. Interesting read.

This isn't strictly relevant, since a) my book isn't finished, and b) it isn't required, but just so you know, I had a few thoughts in response. Probably, I should not be sharing all of them ... but there are Things you should Know.

1) I don't make a dime off of the notes, and it will probably stay this way - writing textbooks is no way to make extra cash. If you bought printed copies of the notes at the SUPe store, you basically paid for the cost of printing - $0.15/sheet, full color. The PDF version online is of course free, and contains no material that is not my own work, or subject to an open-content license.

2) As an aside, the latter point is why many courses have password-protected pages or won't put slides online: they are using copyrighted images somewhere, and cannot just post those things online for free. That is the main reason I spent way too many hours drawing my own figures. Copyright law in the US is byzantine.

3) I don't really worry that you'll read the notes and not go to class. I've even taken and posted video of half the lectures or so, which should in principle worry me even more. I am either naive or arrogant enough to rely on my charm and your sense of responsibility ;-) Probably mostly the latter. Attendance is good for whatever reason, but so long as you learn the material, I'm happy either way.

4) I think the evidence suggests I'm following the notes more closely than the book, and therefore they have some utility. Ideally, you'll read both the notes and the textbook - probably, you will find that Serway et al. explain certain things better from your point of view, and sometimes I do.

5) It is true that sometimes profs do not have a choice of textbook. Particularly for intro classes, and classes where there are multiple sections. There are many reasons for this.

6) It is true that a good textbook is a good safety net when the lecture just doesn't make sense. Sometimes, its not your fault ...

7) It probably is, in fact, silly to spend huge amounts of cash on a book you won't open again after the class ends. In that regard, I wish my notes were complete. Keep in mind that point 5 means that there is almost always a good used textbook market.

Completed HW2 solutions

I finished typing up the homework 2 solutions, which might be a handy thing to study for the exam on Thursday (details to follow).

Also: I did take video of today's lecture, and put up the associated slides.

Lab for Mon 28 July 08

Today, we will investigate the behavior of ac circuits, using your lab boxes ... if all goes well, it should be a short lab.

If you find yourselves with extra time, I suggest hooking up an LED to the output instead of your RC circuit - seeing how the different waveforms behave is interesting. Then, try using the LED in parallel and in series with the capacitor.

Also: I have partial homework 2 solutions available. Probably, they will be finished by Monday afternoon.