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Comment from S. Pollock (CU Boulder, visiting OSU and teaching Paradigm “Vector Fields), Nov 2009:

I have never used Maple before (and our campus doesn't have a license), so this activity will not help me when I go back to CU. But with a terminal at every desk (as we have here at OSU) this activity worked extremely well. I spent  20 minutes on it, leading the students step by step through the Maple spreadsheet. It's written clearly enough that the students were following (and asking or responding to frequent sense-making or “what will happen next” question). When we got to the total flux being “q/epsilon0” at the last step, this triggered a rush of “Gauss' law” recollections. We then went back and I let the students choose a new point to place the charge, and let them redo the calculations. This was great - some chose offset points in the cube, others out of the cube, and naturally one or two smart-alecks went for the corner and were completely baffled by the result. All three made for nice (brief) sense-making discussions with the class as a whole, and the latter (corner charge) was set up as a “think about this one more” ending (there's a homework problem on this from Griffiths)

When we moved to a later activity (Gauss' law), students were spontaneously (or induced by me) going back to this Maple activity to “check” ideas. (For instance, when students later claimed that q_enc=0 MEANS E=0, I reminded them of the student who had put their charge outside the box…)

-S