Question

Which actions most likely cause the domains in a ferromagnetic material to align? Check all that apply.

heating the material
rubbing the material against a magnet
passing electricity around the material
placing the material in a magnetic field of opposite polarity
placing the material near a strong magnet
hitting the material

Answer 1

Correct choices:
- rubbing the material against a magnet
- passing electricity around the material
- placing the material near a strong magnet

Why:
- Rubbing with a magnet, putting the piece near a strong magnet, or running current in a coil around it produce an external magnetic field that moves domain walls so domains line up with that field (magnetizing the material).
- Heating increases thermal agitation (and above the Curie temperature destroys domain order), so it does not align domains.
- Striking/hitting usually disturbs domains and often demagnetizes unless a strong external field is present while striking.
- Placing the material in a field of opposite polarity would reorient domains to the opposite direction (i.e., reverse magnetization) rather than strengthen the original alignment.