You have been given the task of describing the theory of magnetic domains to a class of 5th graders. You have enough large paper arrows to give one to each student. Describe your plan to show them the domain nature ofA non-magnetic materialA permanent magnetAn electromagnet
Sowhat is your question exactly?
This sounds fun. You don't even need arrows really. This is how I'd do it: Put all the students (the more the better--like 100 or more would be great) in a clump in an open space--go outside if need be. Tell them to close their eyes and turn in circles until everyone is facing in a random direction. Now tell them that they are like atoms with magnetic dipoles. No arrow required, just say the dipole moment is in the direction they are facing. If they are facing in random directions, their alignment describes a non-magnetic material. Now tell them that in a permanent magnet, a dipole moment tends to line up with it's neighbors. But it costs energy to move, so it doesn't want to move more than necessary. So tell them to rotate as little as possible to line up with (face the same direction as) their neighbors. Move slowly and no talking. If it works out, you should have clumps of students facing a certain way--those clumps are like domains. Finally, in an electromagnet, an extermal field is induced, which is so strong that it compels all the dipoles to allign with it. So on your command, the students should snap to and line up in your chosen direction. If the material is permanently magnetic, the moments (students) will stay aligned even after the field is removed, because of the influence of their neighbors all facing that way. However, if the material is not magnetic, then thermal fluctuations (like fidgetty students that can't stand still) will have the students facing randomly a short time after the external field is removed.
