I began by having students write the focus question, "How can you use evidence to support your claim about electromagnets?" in their science notebooks. I then asked them what conclusions we made about electromagnets in our previous lesson. Some students claimed the length of the wire influenced the strength of the magnet, and some said it was the number of wraps. I had them go back and look at their notes, and figure out what variable we changed in the previous electromagnet lesson (the number of wraps). I pointed out that we never measured a single wire, so we had no data support the claim that the longer the wire, the greater the strength of the electromagnet.
I asked them to think about how we could find out how the length of the wire affects the strength of the magnet, and this became our new experimental question. I guided them to understand how we could only change the length of the wire and not the number of wraps by keeping the number of wraps consistent. We chose 40 wraps, sort of arbitrarily.
I gave an expectation that each group was required to test three different lengths of wire, at two trials each wire. Each group then sent up a representative to get a bold and a length of wire, and they began wrapping the bolt, same as yesterday. I had to remind them to stop at 40 because they kept coming up with all of the wire wrapped around the bolt. Really long wires should have a lot of extra sticking out. They then came up in groups, same as yesterday, to see how many paper clips they could pick up, and to record their data.
As each group finished, I had them come up to the document camera, and add their data to the class Data Table. After all groups were done, I had one student plot the results in a scatter plot diagram. The purpose of the plot was to help students see that there was no relationship between the length of the wire and the number of paperclips picked up, proving that the number of wraps form the previous experiment was the main thing affecting the strength of the magnet. Unfortunately, you can see in the video that I was the only one who could see that clearly.