Homework 2 results

Just because I know that you are all dying to know ... here is the breakdown for homework 2, average score by question and overall. You'll get your homework back in recitation.
So first: you are really good! The average was 96% overall, very well done on a difficult homework set. Keep it up.

The lower average on #2 does indicate to me that Gauss' law is still tough ... which is understandable. It is hard to get your head around at first, and it is something collectively we need to spend more time on, ideally.

The slightly lower score on question 1 is probably at least in part due to the fact that it was sort of an oddball conceptual question. Once you hear the explanation once, it makes total sense and you'll never forget. Coming up with it on your own is sometimes another story with questions like #1.

Monday is the new Friday

From now on, Homeworks will come out on Monday, and be due the following Monday.

This is being done so that we have covered all of the material well in advance of the due date. Homework coming out on Monday will cover that week's material, giving you the whole week + weekend to work through it.

Homework 3 deadline EXTENDED

Since we didn't get far enough on Tuesday this week, I have extended the deadline for this week's homework to Monday, 4 Feb. at 5pm.

Another reminder: the quiz tomorrow is just an assessment ... so you don't need to study for anything. We just want to know how much you know about electricity and circuits going in to the class so we can see how much you learned over the semester.

Corrections to Notes Ch. 4

I found some bad typos in sections 4.2.1 and 4.2.2 (energy of point charges and systems of charges) which have now been corrected. If you have already printed these or have the bound version, you may want to compare ...

You can download chapter 4 only here.

Public Telescope Viewing 31 Jan 08

As it turns out, we have a large telescope on the roof of Gallalee hall. Want to see how it works? Tomorrow night is your chance ...

The Department of Physics and Astronomy will host a public sky viewing of Mars and the Comet Tuttle tomorrow, January 31, beginning at 7 p.m. at Gallalee Hall. The event, hosted by Dr. Gene Byrd, is contingent on weather and sky conditions.

Lab procedure 31 Jan 2008

Tomorrow, we will do a lab to verify the equivalent capacitance for series and parallel capacitors. Please read the procedure here, and print one copy per group.

Lab procedure 29 Jan 2008

Today we will do a laboratory investigating the electric potential between two differently-shaped conductors. This lab will take the better part of an hour - read the procedure carefully, and work efficiently.

Here is the procedure. You need only print one copy per group.

Quiz 2 results

Once again, you all did very well on the quiz. The average was 81%, which I was quite happy with. Gauss' law still causes a bit of trouble (#3), as do forces in general (#4). Remember, Gauss' law tells us that the electric field on a surface depends only on the total charge enclosed by that surface. If an equal amount of positive and negative charge is enclosed, that adds up to zero, and the field is zero on that surface.

I think the tricky point on #4 is that the electron is far lighter than the proton even though they have equal but opposite charges.

Given the same electric field, they have the same force, but in opposite directions. The acceleration resulting from this force - a = F/m - is greater for a lighter charge, however.

Here is the quiz 2 solution for reference. Note that all of these problems came from the notes directly, if you missed any of these questions, you may want to reread that section and the more detailed solutions.

Homework 3 is out

Here you go. Due Friday, 1 Feb 2008. As usual, we will go over many of these in class. Most of what you need to solve these problems will be covered in tomorrow's class.

UPDATE: minor corrections/clarifications

#1 - write the potential in terms of q1, q2, r, and constants only.
#10 - assume that the spacing "a" is one meter.

Homework 2 solutions

The homework 2 solutions are out.

Homework 3 will be out shortly ...