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UM A3 Video Clip 1: Group 3 discusses their initial models
Group 3 compares their initial models and decides which one to adopt and present to the class. Initially Niki proposes a separation model (which it is what Anna and Faith seem to have too) while Karen proposes a 'layered' model based on her prior experience of breaking a magnet. Niki is persuaded by this. But as they prepare their board for the class discussion they see that their model is different from that of other groups and so decide to present a separation-type model.
UM A3 Video Clip 2: Class discussion of initial models
Group 1 presents their initial model. Then Groups 3 and 7 do the same. In this particular class all initial models were variations of the common 'charge separation' type. At the end the instructor summarizes this type of model.
UM A3 Video Clip 3: Group 1 discusses their final model
Group 1 still has a charge separation model at this point and discusses how to adapt it to account for their observations. They are concerned that they don't understand why the charges rearrange when the nail is cut and discuss this with the instructor. Dawn comes up with an idea that the poles at each end of the magnetized nail may influence the charges in the middle.
UM A3 Video Clip 6: Group 3 patches their final model
Group 3 discusses which model to adopt after the class discussion. While Niki and Karen like the alignment model presented by Group 5 they are concerned that the tiny magnets in that model could be cut into separate N and S particles. Then it would have the same issue as their own (ordered columns of N and S particles). Eventually they decide that their own model can be 'patched'. They assume that the individual N and S particles are so small and so near one another that whenever the nail is cut the particles at the cut are always paired up.
UM A3 Video Clip 1: Group 3 discusses their initial models