We came up with various quantities that could change the magnitude of the magnetic force on a wire. We tested the number of magnets (as a proxy for the strength of the magnetic field), the length of wire, the current through the wire, and the thickness of the wire. (I liked the thickness of the wire test, but we didn't have a good way of measuring the thickness of the wire; I'll see if I can fix that for next year.) We wanted to check temperature, but I couldn't get the equipment together in such short notice. I like the fact we can test lots of different possible independent variables so that when we have our final model, we feel we've investigated everything we could.
We also spent a lot of time talking about the assessment on the electric field model. It was a tough test on a tough unit, and I have to think that some of it was my fault. How can I make the connections between field and potential really strong as well as the connections between potential and energy?