Quiz 3 and 4 solutions are up

Find them here.

Quiz 3

Quiz 3 was all over the map. The average score (across both sections) was 77, with a standard deviation of 19. Looking at the distribution, however:

It has no discernible pattern. Based on the average, it is hard to justify curving the quiz, but based on the number of people at the low end, it almost begs for it.

There are three possibilities here. One is that I just let it go, and a lot of you drop this quiz (undesirable). A second is that I let you do some extra work (perhaps a paragraph essay on the questions you missed), to make up, for instance, half the credit you missed. A third possibility is that I just decide to drop two quizzes for the course instead of one.

I am not promising any of these three, but the last option is probably more likely. I'd rather not have one quiz drag a lot of you down, when in retrospect I can understand where you were tripped up. Some sort of action will be taken, in the end, and by the end of the course the quiz average will be 75-80%, minimum.

HW 2 solutions are up

Find them here. I did parts of them quickly, so let me know if you find any mistakes.

Exam Guidelines

Exam 1 is coming up on Monday. The exam will be held during your lab period, but will take place in the lecture room. It will take you 60-90 minutes. Don't be late. Here's what it will cover:

Electric Forces & Fields (Ch. 15 in the text)Electrical Energy & Capacitance (Ch. 16 in the text)
Current & Resistance (Ch. 17 in the text)

See the course schedule for the particular sections in each chapter you are responsible for. Note also that relativity is absent. The material we cover tomorrow (Friday) will be on the test.

The format of the exam will be (approximately) 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. 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 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.

More details will follow over the next couple of days. For now, I suggest reading the chapters and old homework/exam solutions.

Slides from today's lecture

... are up here. I'll use the same slides tomorrow to finish current/resistance and start with dc circuits.

Friday's quiz

Tomorrow's quiz will derive entirely from Ch. 16 in the textbook, or the equivalent sections in the notes.

UPDATE: I swear this one should be easier than the last one.

You will need: 1) the rules for combining series and parallel capacitors (formulas given),  and 2) the rule for calculating energy stored in a capacitor from voltage and capacitance (formulas also given).

One thing I haven't mentioned explicitly: if you put batteries together in series, and connect them plus-minus-plus-minus, you add the potential differences. So, two 3V batteries connected in series with the same polarity gives 6V. Charges moving through the batteries in series would get a boost of 3V potential difference from the first, and another boost of 3V from the second, and thus each charge acquires 6V potential after moving through the two batteries in series.

Two 3V batteries connected with opposite polarities (so plus-minus-minus-plus) usually leads to zero V, and undesirable behavior.

Thursday's Lab

Today, you'll investigate the equipotential lines around some charged conductors.

Sorry for not getting this up earlier ... I had my days mixed up.

Powerpoint slides used in class

Here you can find the powerpoint slides I used in class, along with a few extras I didn't. I have the slides from relativity, electrostatics, and electrical energy up at the moment.

(If you are in the pm class, I didn't use as many slides due to the room being inconvenient, but you might find the slides useful anyway.)

Problem-solving template

In past courses, I've tried off and on to have students use a problem-solving template that my colleague Prof. Mankey developed. The basic idea is to give you a general structure for solving problems by compartmentalizing the problem-solving process. Break it down into fairly general steps that most problems have (though not always in the same order) so you have a guide for how to start and finish problems.

The template is not something you will be required to use when solving problems, but if you're having trouble with the homework, it might help. Details below the fold ...

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 ...)

HW3

I'm a bit late putting out the next HW ... it will come out tonight, but not be due until Friday instead of Thursday. Check back tonight ...

Wednesday's quiz

Wednesday's quiz is all about charges moving through electrical potential differences and electric fields. E.g., if a charge q moves through a potential difference of V, how much energy is gained or lost? If a charge q is placed in an electric field, what force does it experience? What is the difference between the motion of positive and negative charges? You'll have to recall what we talked about Tuesday, along with the basics of PH101 - relating force, mass, and acceleration.

There will be plenty of useful hints about the quiz in Wednesday's lecture.

HW1 solutions

HW1 solutions are out, you'll get them back (along with quiz 2) during Wednesday's class.

Wedensday's lab

Wednesday's lab will be all about capacitors, or at least how they combine in parallel and series.

You can find the procedure here.

Apologies for posting it a bit late, but please read the whole procedure before getting started with anything and start connecting wires, capacitors, and power supplies all willy-nilly.

Big safety hint: make sure your power supply is turned off, and maybe even unplugged to be sure, before wiring up your circuit. Before turning on the power supplies, make sure the voltage and current knobs are turned all the way to zero.

Capacitors can react angrily to a sudden spike in voltage, and the magic smoke inside may escape ...

Quiz solutions

Quizzes 1 and 2 and their solutions are up, find them here.

Homework 2 / Monday's lab

Homework 2 is out, due by the end of the day on Tuesday. We'll go over most of them in class by the end of Tuesday.

Monday's lab will be a series of Java applets that will help you get a 'feel' for electrostatics. You can find the applets here, and the procedure here.