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

Ran this “kinesthetic activity” last  20 minutes or so of lecture 4. Props: I used a voltmeter as standin for a magnetic field probe, and used a 2meter stick for measurements.

I had seen a video of Corinne Manogue doing this activity, which helped me a lot. I stood on the table (as she did), holding a “magnetic field probe”, and got all students to stand up. “You are all positively charged” Here was the string of activities we did:

1) Please move, so that my B field meter fluctuates. 2) Now *move*, but keep my B-field meter steady. (This generated immediate discussion: Can they move in a straight line? Sure, but they'll need to keep going, and it requires an infinite “line” to keep feeding into the room. Then they realized they can circle - the room is cramped and the circle is funny shaped. Did that matter? Did their *spacing* matter? At first, one student “split off” from the others, did that matter?) Naming: this is a current (or linear current density) 3) Now make me a surface current density, but keep the field-meter steady (Again, some quick discussion: Again they wanted to go back to a straight “ribbon” motion. Could they go in a circle and yet be a surface current? One student joked that he didn't know what a record platter was, when I invoked it) 4) Can you make me a *volume* current density? (Just talked about this) 5) Stand still, in “line” configuration. What do I need to measure to get lambda? (Generated discussion - need a ruler, need charges/unit length) 6) What would I need to measure to get sigma? rho? 7) Now move - what would I need to measure to get current? (Lots of discussion and ideas, settled on “charges passing/second” 8) What would the “gate” look like that measures current? (point? line? area?) 9) What if they are a surface current density, what do I need to measure to quantify K? (Discussion about the fact that it's current passing a perpendicular LINE measure, not per unit area!) 10) What do we measure to quantify J? 11) As they walked around as a current one last time: what do I need to know *besides* lambda to calculate current? And, how?

At which point I went to the board (they sat down) and we talked through I = lambda * v K = sigma*v J = rho*v The class generated all three of these, we talked about UNITS, and why I = lambda v works…

Overall summary - couple students appeared perhaps a little uncomfortable standing and walking, though there were also *lots* of smiles. Definitely generates some fun moments, especially nice at the couple of puzzlers (like making a uniform field, and then again uniform field from a surface current, or even the “gate” for a surface current) where they had to talk and work together.

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Comment from R. Pepper (CU Boulder, substitute teaching for E&M1 and CU), Spring 20010:

I used part of this activity to supplement a lecture in which steady current was defined. I only asked students to make a steady current – they quickly made a closed rectangle around the desk I was sitting on. Even this shortened version of the activity (lasted less than 5 minutes) was very productive, as students brought up several questions, such as “is the current still steady when I'm moving around the corner of the rectangle?”

I was hesitant to use a kinesthetic activity, as I was substituting in a class which hadn't used kinesthetic activities up to this point, and I was worried the students wouldn't participate, or that I would lose their respect. This did not happen. It took a little encouragement before students got out of their seats, and there were a few students who never really joined the activity, but observed standing nearby. I was able to involve them, by asking how the moving charges looked from their perspective. All of the students seemed to enjoy the activity, and one student commented to me after class that he had found it helpful. I did not feel that the students lost respect for me after this activity.