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.

Lab grades

You now have many lab grades posted on Mastering Physics.

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).

Relativity HW extended

I'll push the deadline for the relativity HW until Friday so you can worry about the test more efficiently.

This will not affect the HW2 deadline, nor the occurrence of HW3 shortly thereafter.

(This is for Dr. LeClair's section only. Dr. Mazumdar may or may not decide to do the same.)

Intro & relativity slides

Here are the slides from the first two lectures, which contain the intro/syllabus information and some figures for the relativity material.

More grades

HW5 grades are now posted on moodle. If you don't have a score for HW5, but are sure you've turned it in, feel free to remind me. I didn't quite get through that stack of homework this evening.

HW6 & 7 grades will follow tomorrow evening, along with some of your lab scores. Most of the lab scores you know already, but I will post what I have from the TAs tomorrow.

Exam II grades

Your exam II grades are up on Moodle ... you'll get them back tomorrow. The average was 85/81 for the am/pm sections, so most of you should be happy. I was, anyway.

Tuesday, I should have the homework and quiz grades mostly up to date, and I have more lab grades from the TAs as well. At the very least, before the final you will know what your grade is going in.

Today's lab

ac circuits.

Online grades

I swear, I was getting ready to post grades online, and the power outage this evening brought down the server I need ... it should be up by 08:00 Tuesday, so Tuesday evening I can finish the update. I have graded all quizzes and all but the last HW set, which you'll get back tomorrow, but you'll have to wait one more day before I get grades online.

Hopefully Tuesday evening you will be able to log in to the open-source system I have set up to access all your grades. The server I have the software on did not power cycle well, so I can't finish uploading your grades to it until someone physically reboots it Tuesday morning.

(FYI, it is a secure system that you log in to, and I will post instructions on how to access it and determine your login and password. It is, in my opinion, less clunky than eLearning, and vastly easier from my end.)

It figures that I delayed one more day and this happened ... there is a lesson in there somewhere about procrastinating I guess.

Today's lab

Sorry I forgot to put this up earlier ...

Today, you'll explore RC circuits, which we covered last week and will come back to next week when we discuss ac circuits and audio filters.


Before you do the lab, however, I'd like you to explore this applet on circuit construction. There are no real instructions, just spend 10-15 minutes constructing different circuits to get a feeling for how things work. Of particular interest is the 'grab bag,' from which you can choose various household items and try to run current through them. Too much current, and you will start a little virtual fire ...

In other news ...

Remember what I said about photons having momentum, and how one could use that for spacecraft propulsion?

Done. Very cool stuff, though the linked summaries are somewhat ... lacking. Knowing what you know of relativity and mechanics, can you spot some places where the articles are incorrect or misleading?

HW3 is out

Homework 3 is now out. Since I'm late by about a day getting it out, I'll push the deadline back one day ... so this is due by 11:59pm on Friday, 16 July.

We'll go over most of these problems Thursday and Friday in class, at least enough to get you started.

(This means you have no HW or quiz tomorrow, but you have both on Friday ...)

HW8 is out

Here you go. Have fun, it is due Monday 3 Aug by the end of the day.

Why, yes, it is a thinly-veiled attempt to get you to read the chapters ;-)

Einstein on induction

Here's what Einstein had to say about magnetic induction:

Imagine a conducting loop moving relative to a magnet as seen by two different observers: one on the magnet the other on the loop. Both observers see the identical EMF generated in the coil using the flux form of Faraday's law, but explain the result using two different reasons. The observer on the magnet sees the magnet as stationary with an unchanging magnetic field, while the conducting loop moves. All of the charges within the loop move with the loop, and due to the B-field experience a sideways Lorentz force, which generates the EMF. On the other hand, an observer on the loop sees a changing magnetic field due to a moving magnet (relative to the loop's reference frame) and no Lorentz force (charges in the loop are not moving). This changing magnetic field means ΔB / Δ t ≠ 0, which creates an electric field that generates the current.

This is what I was trying, less eloquently, to explain this morning.

The plan for Tues, roughly

Basically, we'll finish up electrical energy & capacitance.

• More details about the exam ...
  
• Review HW2 problems
• Review of electric potential - relation to PE and work; point charges
• Systems of charges - potential energy and stability of crystals
• Isolated conductors and equipotential surfaces
• Review of capacitor basics - adding in series & parallel; parallel plate capacitors
• Complex capacitor combinations - how to analyze
• Capacitors with stuff inside - dielectrics & dipoles in electric fields

Relativity

Couple of random comments, since Tuesday's lecture probably seemed really tough.

(1) I think relativity is the hardest stuff we cover. We cover it first because we can make use of it later in a good way, and because it follows PH101 more logically.

(2) Particularly the first day, relativity is really bewildering. Typically, it makes a lot more sense on day 2, when we get a little bit further along and start to apply it in a concrete way. It is something like 'day 1: why things are weirder than we think' and 'day 2: shut up and calculate.' Day 2 is usually where things make more sense, or at least one just trusts the formulas we developed and tries to figure out what one can do with them.

(3) Based on the above, don't get too worried if today seemed like a rough start. It will make more sense on day 2, and the subsequent material is conceptually easy by comparison.

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.

Lecture video continues / Homework II

I have continued to post videos of the lectures, fyi. If you have missed some class lately - and some of you have - they might be worth some of your time.

On an unrelated note: I have moved the due date for Homework II to Tuesday, 22 July so you don't have a homework set and an exam on the same day.

Exam II solutions

Here you go, for the last-minute cramming.