What important physics idea is this question targeting?
This is targeting whether or not students recognize that an iron nail can be modeled as misaligned tiny magnets, and those smaller magnetic regions align when magnetized. (C)
This task addresses how a magnet can polarizes charges within an iron nail to create a north and pole within the nail. (I)
This examines how students think about where magnetism comes from and their abilities to represent models. (V)
Student A's response:
Which answer best describes what student A's response indicates about their physics understanding?
This student recognizes that the magnet does not add magnetic poles to the nail. However, they think of the poles in a magnet as needing to be energized, instead of the magnetic poles that comprise the nail as each having a fixed strength.
This student thinks of the nail as being made of magnetic charges (N and S) that are concentrated at the ends of the magnet as opposed to distributed throughout. (So so)
This student has strong ideas but has not yet learned the correct terminology for poles / charges and energized / polarized. (V/I)
Which of the following options would best support Student A in being able to correctly respond to this question?
I would affirm for them that the magnet must add energy to the nail, but would also note that north poles inside the nail cannot get stronger or weaker, but instead has to do with how the north and south poles are aligned. We could then try to develop models in which the "N" and "S" poles are always present with the same "strength." (C)
I would have them predict what would happen if we cut the nail in half, and then have them watch a demonstration to see that each half of the nail still has both a north and south pole. (I)
I would ask them to find someone else in the room with a different model from them and discuss the differences. (V)
Student B's response:
Which answer best describes what student B's response indicates about their physics understanding?
The student thinks of the nail as comprised of many disordered magnetic charges of equal and opposite strength that become separated into two poles by the magnetic field of the permanent magnet. (C)
This student pictures the nail as having tiny disordered north-south pairs that are misaligned, but the magnet aligns each of those small regions so that the norths are on one side and the souths on another. (I)
The student is able to draw a complete model but has not offered any explanation for why they think this. (V)
Which of the following options would best support Student B in being able to correctly respond to this question?
I would agree with the student that this model accounts for the data, and ask them to make a new prediction for what this model suggests should happen if we cut the nail in half, and then have them watch a demonstration to see that each half of the nail still has both a north and south pole and revise our models. (C)
I would ask them to repeat the experiment on their own using a bar magnet and a nail, and then use a compass to confirm whether or not the nail is polarized in this way and then use that evidence to write a strong claim-evidence-reasoning statement. (I)
I would ask them to find someone else in the room with a different model from them and discuss the differences. (V)