fun developing the Coulomb lab

I had a fun morning developing different ways to explore Coulomb's law, trying to find a way where students could get reasonable data on the 1/r^2 dependence. We eventually settled on the repulsion between the end of a charegd rod and a pithball on a thread. By suspending the ball just above graph paper you can get reasonable measurements of both the separation between the charged objects and the how far the pithball is deflected from the vertical.




For each separation the static equilibrium condition of no net torque gives you a measure of how the repiulsion depends on separation, the results were pretty close to 1/r^2 ! It was definiately fun futzing with alternative ways to create setups.

how do we know that there are just two types of charges

I'm planning to start the semester off by challenging the students with the question "how do we know that there are only two types of charges". May be useful to emphasize the nature of science, but also may go over with a thud, depending on whether students are already convinced that there are only two types of charges.

Note that it took from ~600 BC to 1800 AD, almost 2500 years, for humankind to reach the understanding that there are just two types of charges. And I plan to do this in ~30min!

different lab sections

When I teach 222 I enroll all my students from the registrar side into one webCT course. However each student is officially listed (on the registrar side) as being part of a separate recitation section and a separate lab section.

The lab sections meet once a week, each lab section at a different time per week and they have an quiz/assignment due just before the lab meets, this is a pre-lab. When I have all the lab-sections in the one-course, I can’t close the pre-lab till the very end of the week, after the very last section. I’d much rather close this at the right time for each section.

A possible solution is to create a) 222 webCT all_sections that everyone enrolls in b) then ~ 20 webCT courses: one for each lab-section that only has the lab info in it. Perhaps start with a template lab-section and clone it. Each student would be enrolled in the all_sections course and their lab-section. I would then perhaps create each pre-lab on respondus, upload each pre-lab to each of the webCT lab courses with different dates of each pre-lab, 14 of them in each of the 20 sections :( = 280 respondus uploads, yuck. Unless there is a smarter way to do that.

more open-ended labs

I have taken the opportunity in this past week to make more of our labs "open-ended". Rather than asking students to follow step-by-step procedures and hope they grasp the physics implications, part of the labs will ask the students to verify or test a physics principle.

For example in the magnetic field lab, they will be asked to establish the extent to which the approximations used in applying Ampere's law are accurate for a long wire and an solenoid. The plan is to have the first part of these labs follow some step-by-step examples to help students get familiar with the equipment.

Wonder what sort of evaluation I should do

draft sequence set!

I have now finished the first draft of the sequence and have been able to include a few more lectures that will focus on problem-solving: most probably via a guided problem. Now onto the labs

starting to plan for Spring 2009

I'm starting to plan for the new semester and am pretty excited about it. First priority is to figure out the number of lectures for the new material in 222, e-fields