Navigate back to the activity.

I started this activity before doing the power series activity. My goal was to provide a little more physical motivation for power series, and to break up the math (we just did “distance between two points”) with some physics. I just had students write down a general expression for the potential due to +Q charges +/- D from the origin on the x-axis. After power series, we will come back and do the main part of this activity - using series expansions to approximate the general expression in various special cases.

When we did the full version, I had each group do the first case, then asked each group to do a different second case. That way, we had a common starting point as well as different cases for a compare/contrast discussion.

We did not have time to get to or discuss all the cases. This often happens in these activities, and when time is short, I usually choose to do a wrap up discussion rather than push to finish the last case or two. This allows us to connect to the bigger picture, make a few important points, draw implications, etc. It's productive for the students to do the remaining cases on their own (I often make this a little HW assignment), and after working in class they should be prepared to do this outside of class.