Grades

I have updated grades on MasteringPhysics, which includes exam 3 scores and your overall grades. Have a look.

Exam 3 wasn't too bad, but I did scale it a bit. After scaling up by about 6 points for everyone, the average was 78.5 with a standard deviation of 10.5. Not quite as high as the first exam, but on par with the last one.

Most of you stayed about where you were at going in to exam 3, and the grades didn't change much overall. I'm not saying everyone is going to be happy, but most of you should feel pretty good about how you did - the overall class average was a solid B, nearly a B+.

Anyway: I'm not going to post final grades on myBama just yet, not until I've reviewed everything a few more times. If your grade ended up within ~0.5 points of a grade boundary (say, 89.5), I will carefully review your grades and re-grade your final exam to make absolutely sure of your grade.

Calculating final grades is agonizing, and I hate having to break a whole semester's performance down to a single descriptor. Not my idea though, has to be done ...

Last exam

I will scale it if necessary.

I am a bit perturbed by how difficult the exam seemed to be, since over half the questions were either from previous exams or covered in class. I think some of you know now that 'open book' does not mean 'won't study, I can just look stuff up.'


Q1 - similar problems on many previous exams, spent a lot of time in lecture on this.
Q2 - you a lab on this, examples in book
Q3 - almost identical to previous exams you had access to
Q4 - you need to multiply by volume=Ad and use E=V/d, no tricks
Q5 - directly from previous exam
Q6 - on previous exams, done in class, basically an example from the book ...
Q7 - I did this in class, exactly the same problem.
Q8 - just need mirror definitions, no tricks
Q9 - directly from previous exams
Q10 - need only the photoelectric equation for both pairs of data

Anyway, the thing is done now. I'll have it graded over the weekend at some point, and will put the grades on MasteringPhysics. I will scale it if need be, we'll just have to see how it goes.

Grade updates / last class

If you gave me lab grades that needed to be corrected, I think those should all be done now. Please check through your lab grades and see that everything makes sense. The paper grades (lab 1) are in now as well - so if you wrote a paper, make sure you got a grade ...

The only outstanding grades other than exam 3 are now the Planck's constant lab and the last HW due Wed night. We'll go over those problems in class tomorrow (Wed) so you can get them done quickly after the exam [I'm just going to go ahead and assume many of you are putting the last one off, it seems reasonable].

Tomorrow's lecture is being decided right now ... probably we will go over energy levels in atoms and solids, but one never knows what I might do at the last moment. In any case, tomorrow's lecture material will not be on the exam.

Last summer's final

UPDATE: here are answers and sketched solutions to (only) the questions relevant for tomorrow's exam.

For your studying pleasure, here is last summer's final. I can't find my key, so I'll have to do all the problems quickly before I can post the answers ... but I will post them later this evening.

Other things this evening: grade updates (including fixing lab grades you've brought to my attention), and some hints for the exam.

Tentative exam 3 coverage

This is all pending a discussion with Dr. Mazumdar so we can coordinate ... but here are the minimal sections you should worry about:

22.2,4 reactance & power in ac circuits, there is certain to be a question about filters
23.1-3, 5-9 EM waves
24 all (geometric optics, but you won't have to draw ray diagrams)
28.1-3, 6-7 quantum and atomic physics, note in particular the Bohr model

Tentatively, there will not be any questions from Ch. 29 since that is almost purely qualitative stuff.

The test will be open book & notes, the only restriction is that no internets are allowed (i.e., no phones, PDAs, laptops, etc.).

And, very important, both sections will have the exam at 4pm on Wednesday in the usual lecture room. You will have at least 2 hours for the exam, and will probably not need all of it. If, for some good reason, you cannot make it from 4-6pm (e.g., job constraints, another class, etc.) we will work out an alternate time, but please contact me as soon as possible.

There will be 10 problems out of which you must solve 8, and they will be shorter problems than the previous exams. That is, don't freak out about there being more questions than before, the questions will be much less involved than usual HW or exam problems. They will be at the level of example problems in the book, for the most part find the right formula and go. Nothing really subtle.

More details tomorrow (Tues) after Dr. Mazumdar and I discuss a bit more ...

Exam 3

Chapter 26 (Interference and Diffraction) will not be included in Exam3. Chapter 30, on nuclear physics will also not be covered.

The exam will be open book. Bring your book and any scribbled up piece of paper that you might want.

Exam 2 scores are up

Check it out on Mastering Physics.

It wasn't that bad - average of 79.3, standard deviation 8.7. I was basically happy (though all of you might not be I guess ...). Here's the distribution, the bulk of you were in the mid-C to mid-B range.

More on this during Friday's class. Above all, do not panic: we have one exam to go, and almost no one is in any sort of danger.

Labs grades were updated as well, have a look. 

Today's lab

Today, we'll do two little experiments on mirrors & snell's law, and one on lenses:

http://faculty.mint.ua.edu/~pleclair/ph102/Labs/reflection_refraction/reflection_refraction.pdf
http://faculty.mint.ua.edu/~pleclair/ph102/Labs/lenses/lenses.pdf

Even though there are three experiments, overall it is still very fast and should not take the whole period.

In other news, the tests should be graded tomorrow. I will also extend the current HW deadline since I was out, but the next one will come out tonight (due Sun).

Makeup exam questions

They are graded, and you'll get the back tomorrow. Not on Mastering yet, but hope to update that on Tues.

The 2nd exam should be graded by Thursday - I didn't get them back this evening to get started due to a mix-up, but I'll grade them as quickly as I can.

Old exam answers

Exam 1, summer 2009, problem 4: this was also on the summer 2008 exam 2.

Exam 2, summer 2010: only the first three problems are material related to your upcoming exam.

1. Just walk around the middle loop - that gives 12-6I=0, and determines the current in the 6Ω resistor to be 2A.

2. Use the right-hand rule to determine directions. Two of the currents give fields pointing to the lower right corner, and two of them give fields going to the lower left corner. All fields have the same magnitude (same current, same distance; watch the geometries). All but the vertical components will cancel; find those and add together. The net field is in the -y direction, and has magnitude (field of 1 wire at center)*(sin 45)*(4 wires)~5e-6T.

3. (a) into the plane. (b) set r=mv/qB equal for both particles using the known electron and proton masses. q is the same for both, and will cancel, as will B. This gives (v_e/v_p)=(m_p/m_e)~1.8e3

4. (a,b) This filter passes speech - the inductors let low frequencies through, and the capacitor shorts out any remaining high frequencies. (c) Add all inductors together, they sum to 10.26mH. The cutoff frequency is when the inductive and capacitive reactances are equal, so f=1/(2*pi*sqrt(LC))~10.6kHz

5. This is motionally-induced voltage, like the conducting bar. (a) V=Blv~2.5mV (b) Right hand rule gives the force on a positive charge toward the drivers door, so it is the positive side.

exam 2 coverage

The following sections are fair game for the exam: 19.1-8, 20.1-9, 21.1-9.

I am aware that there is no solution to summer 2010 exam 2. I will do what I can tonight.

You did not have any homework on induction (yet ...), but it is still on the exam. Check out the old hw, exams, and solved examples in the book for some practice. We will probably have time to do a few more in class tomorrow.

There is a formula sheet essentially identical to the one you will receive on the exam here.

Exam scaling

Long story short, just taking the total points on the last exam and grading it out of 100 instead of 120 is not really fair to those who only did 5 problems (like the instructions said). Doing it any other way makes it unfair to some other groups of students.

So here's the deal. If you did only 5 problems on the exam, during Thursday's lab you can solve one more problem to add to your test. No down side here. Exactly the same rules as the exam, except you don't have a choice of problems.

If you did 6 problems, but got only 1-5 points on one problem (i.e., the token partial credit for writing down *something*), I'll let you take the makeup problem on Thursday to replace the problem you only got token points on.

If you did 6 problems, but still feel your score could be better, then you should make a specific appeal ... I might be willing to let you replace one of your problems, and I might not, depending on the situation. Probably not if you're just aiming for that A+. Probably so if you are worried about failing. So it goes. One can't be completely fair in all things, but we'll do the best we can.

Exam 1 grades

I've posted exam 1 grades on Mastering Physics now. I ended up taking the total number of points you got from all problems you did, and just taking it out of 100 instead of 120.

I arrived at this procedure by first calculating your grades that way, and also separately taking the best 5 out of 6 problems. In all cases, the first method gave the same or better grade, so I opted for the second method. That gave an average class score of 81% with a standard deviation of 15%, pretty reasonable. I was also happy that choosing this method meant substantially fewer people ended with Ds and Fs on the exam.

Anyway: please check your posted scores against what is marked on your exam (and also make sure all the points add up right on the exam) so there are no errors.

Eating candy off of the ground

Using equations at random is like eating candy off of the ground.

Solutions to Sum10 exam 1

Some very quick solutions to the Summer 2010 Exam 1.

Exam practice problems

Your best bet is to dig around in the exams from previous incarnations of PH102 - just about all of them have solutions too.

http://faculty.mint.ua.edu/~pleclair/ph102/Exams/

Look at the first exams for any given year, the one from Summer 2010 is probably most relevant. Old HW problems are also good, and almost all have solutions:

http://faculty.mint.ua.edu/~pleclair/ph102/Homework/

The only trick is that HW problems are usually harder than exam problems (at least in the past, when I didn't use online HW).

Exam format

I had a couple of questions about the exam format, etc., so I'm reproducing my answer here for the rest of you to see.

The test will basically be 6 problems, and you can solve any 5 of them - so you can skip the one you think is hardest. Each problem will have multiple parts, so there is plenty of chance for partial credit (even within an individual part). A good example would be this one: 

http://faculty.mint.ua.edu/~pleclair/ph102/Exams/Sum_2010/ 

(This exam from last summer had them solve 6 of 8, but that ended up a bit too long). Again, heavy partial credit if you seem to more or less know what to do, but just make some small mistakes, or just get part of it right.

The formula sheet is totally unrestricted so long as it is 1 page of normal paper on both sides, or two sheets with only 1 side of printing each. Otherwise, it can have on it whatever you like.

Exam 1 is soon

Exam 1 is coming up on Thursday. It is rather soon, but there are reasons for this ... The exam will be held during your lab period, in the lab room. Even if you have my lecture and the 5pm lab, you still take the exam during your normal lab period. It will take you 60-90 minutes. Don't be late. Here's what it will cover, just two chapters:

• Electric Forces & Fields (Ch. 17 in the text, all sections)
• Electrical Energy & Capacitance (Ch. 18 in the text, all sections)

Note that relativity is absent.

The format of the exam will be 6 problems (i.e., solving stuff, no multiple choice), you pick any 5 to solve. Put another way, I'll give you 6 problems, you can skip any one of them you like, they are all worth the same amount. To head off an obvious question: if you do all six, I may grade all six and take the best 5 as your grade. Or, I might just grade the first 5. Who knows. Your best bet if you do all six is to tell me which 5 you want me to grade.

I will provide a formula sheet (example) with all relevant constants and basic formulas, a list which should be sufficient to solve all problems. Additionally, you are allowed to bring in a single 8.5x11 inch sheet of paper with your own notes, formulas, etc. -- anything you want, really. Front and back sides are allowed, I will allow two sheets with only a single side if you prefer that. You are additionally allowed writing implements and a calculator (i.e., not a cell phone or any network-enabled device). You can feel free to program your calculator in arbitrary ways, however, just no internet or peer-to-peer communication of any kind.

I don't know if I can stress enough that you should not forget your calculator.

Random Things

Thing the first: I really think the electric potential stuff will 'gel' for you quite a bit after the next lecture. We've just touched on it so far, in the next lecture we'll look at some practical problems and how to really use potential for calculations. We'll also be moving into more concrete subjects - the energy of crystals, circuits, etc. - and you'll have a little more intuition for what's going on. So, it is a lot of information at once, but be patient. There is a plan of sorts, and by exam time you'll be vastly less confused ...

Thing the second: check out the right sidebar. The 'course notes' are very extensive (nearly a complete textbook), and very close to what I follow in lecture. Following both the notes and the book is not a bad idea - if a section in the book doesn't make sense, try the notes & vice versa. They treat the same subjects slightly differently, you might find one explanation more to your liking than the other.

Thing the third: there are also many, many solved HW and exam problems you can access from the right sidebar. If you want example problems, or want to see what I've asked before on exams (the presumption that I will ask similar things is a good one), there you go ...

Thing the fourth: if you are in Dipanjan's section, we are going to have the same exam, same format. Details to follow soon ...

Final grades

UPDATE 2: I think all the + and - parts are fixed now. I will check again shortly and again (later) in the morning.
UPDATE: Bear with me, I put in some of the + and - parts in wrong in myBama. Correcting it now, should be done by 01:30.

I am about to put up final grades on Moodle, and then on myBama. By the time I hit 'post' on this thing, they should be on Moodle already. There will be a new column called "Final Grade" which is just what it sounds like. The difference between this number and the "Course Total" is due to the bonus you may have received for improving on the assessment test, and extra credit if you did it. As before, please let me know if anything seems to be in error (e.g., missing HW or lab grades).

If there is anything I hate more than having to boil your entire performance down to a single letter (perhaps with a + or -), I don't know what it would be. It is agonizing to try and decide who gets what, and I end up sitting in front of the spreadsheet for hours making sure I didn't miss anything. It is by far the worst part of the job, I would much prefer to just say 'yea' or 'nay' and be done with it. What really happens is this: I grade the final exams twice, check the spreadsheet many times, and then look at each calculated final grade. If you're close to the borderline between grades, I look a few more times at your individual grades, and take yet another look at your final exam. I do what I can, and round up where I can justify it, but it always ends up that some people are just short of a letter grade, and it can't be helped.

In the end, after the final exam some of you moved up a letter grade, and some moved down. That's how it always ends up, and as a result, some of you will be happy and some of you will be quite unhappy. I hate to see people move down based on the final exam, but it has to happen in some cases, given that it is worth 25% of your grade. I was generally pleased with how it came out. A few of you really pulled yourselves up on the final, and that was good to see. A smaller number of you made a significant drop, and that is the main reason I spent a few hours going over each final exam one more time to be certain.

Anyway: I had a lot of fun this summer, and it was a pleasure to have all of you. Whether or not your grade came out how you wanted it to, I hope it seems fair at least, and more importantly, I hope you learned something useful.