Today's lab

was probably a bit hard for you. That is OK. There are really two reasons for this.

1. Scheduling. I chose to do relativity first, the other two classes I have to stay synchronized with lab-wise did not. My way is sort of a pain on the instructor (not following the textbook order for one), but I think the course as a whole ends up more coherent. Also, the PH106 section we're syncing with doesn't even cover relativity at all. As a result, for the first week or so the labs come a bit sooner than I would like. This will be resolved next week.

2. Realism. You walked into the lab knowing only a little bit about capacitors, and then were expected to figure out how they acted in combination - while also knowing next to nothing (on average) about the power supply and meter you were supposed to use. This probably meant you were confused at first, had to read and think a bit, and ask a lot of questions about the equipment. It is frustrating, but this is a much more realistic picture of how real experiments work - many unknowns, all you can do is be systematic and careful. It is more a barely-guided exploration, driven by your inquiring as to how things work, than baking a cake or assembling some Ikea furniture. There is never a complete recipe or instruction manual that will always work. We can't do all the labs like this - just throw you into the fire, as it were - but I think it is a good experience to just turn you loose with minimal preparation and see what you can figure out some times. We will do some 'cake baking' labs too, but doing only those gets boring.

That being said, tomorrow in lecture we'll discuss capacitors, meters, and circuits in detail, and I think in retrospect everything will make sense, and you'll have a better appreciation for what you did today.

Tomorrow's lab is a milder version of the same thing - we're going to turn you loose with various electrical components and see what you can make them do. It will be less difficult than what you did today, but will still involve an element of exploration that is really key to proper experimentation. 

Photons

A nice post on how we know they exist. A great blog if you want to learn a bit more about physics.

Notation

So we've discussed the fact that physics notation has quite a bit of historical baggage, and lacks precision at times (same symbol, different quantity ...).

Counterpoint.

This is a problem in teaching physics

Precision in language is important, but it is a slippery slope.

Another day in the kingdom of fear

I'm glad we're still letting you do real, live labs with real, live equipment. Unlike these geology students, who can't have real rocks ...

(Or, heaven forbid, you try to find a chemistry set anymore. Sigh.)

So, even if you don't particularly like the labs, you can consider it something of a privilege to be allowed to do them anymore ;-)

Things which tempt me greatly

This.

As the undergrad adviser for physics and astronomy, I enjoy giving undergraduates advice. Occasionally, however, when confronted with a vague question, it is hard to resist the temptation to be a bit silly ...

With regards to the link above, I'm thinking of some sort of Fight Club crossover, "My class is Jack's inflamed appendix."

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?

Homework submission

Just a couple of things that will make grading easier for me:

1) Putting your last name in the filename you send helps a lot, so I don't have to rename everything. For example, "p_leclair_HW1.pdf" is really handy. "leclair_p_HW1.pdf" is even better, since it alphabetizes nicely I look at all the files together.

2) If you know how to do it, combining separate scanned pages/pics into a single file is good, but don't spend too much time figuring it out if you don't know how. I can suggest how to do this on various platforms if you're interested.

3) If you turn in a hard copy, I don't necessarily need a copy of the problem set itself, you can just turn in your work.

4) Include "PH102" in the subject line of the email, and possible HW1 or something like that to help the filtering.

Basically, it costs a little more time if I get 30 emails with a subject like "homework" or "physics homework" and filenames like "homework.docx" or "hw.jpg". I can sort this out very easily, I'm mainly pointing these things out because it probably isn't something you thought about. I wouldn't have either, until I started taking email homework submissions.

These are really just suggestions, I'm happy to deal with any sort of files you send. I can read pretty much any file format you can think of (that is not a challenge, btw), and keep things pretty organized, so it isn't a huge deal. The main point is: if you can save me some seconds per submission, this is nice because I have 68 students between two sections.

Just to reinforce: there haven't been any problems at all so far, even with the cell phone pics (many of you have good phones, it seems), I'm just letting you know what would help if it isn't difficult for you.

Also, thanks for the cat pictures. Nice looking cat.

Today's quiz

That circuit from the quiz today is often called a diode snubber, or a flyback diode. Very handy protection circuits; one can do similar things with an RC circuit (or low-pass filter) to buffer out rapid changes in current/voltage in a circuit.

Anyway: I didn't just make it up.