Electromagnets NOT Becoming Permanent
Why doesn't an electromagnet become a permanent
magnet over time? It is magnetized by electricity so what makes it
not become a permanent magnet?
There are only a few materials that CAN become permanent magnets. Almost
every atom is magnetized. Most of the time, the atoms in a material are
directed a variety of directions. Without any alignment, the total effect
is zero magnetization.
If the atoms can rotate easily, an electromagnet can cause some of the atoms
to align. This alignment then amplifies the magnetic field, making it a
stronger electromagnet. When the electricity turns off, the vibrations and
bouncing around of atoms within the material quickly eliminates any
alignment. These materials are labeled as paramagnetic.
For some materials, the magnetic attraction between atoms is unusually
strong. Small groups of atoms align all by themselves. As before, an
electromagnet causes large numbers of atoms to align with each other. When
the electricity turns off, the atoms are strong enough to hold many other
atoms in line. These materials are labeled as ferromagnetic. Iron is
probably the most common element.
Even with ferromagnetic materials, some get atoms get out of line. Dropping
such a magnet on the floor shakes up even more atoms. This is a way to
demagnetize a magnet. Heating up the magnet can have a similar effect.
Dr. Ken Mellendorf
Illinois Central College
Update: June 2012