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Name: Robin
Status: other
Grade: other
Location: FL
Country: N/A
Date: 11/29/2005


Question:
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?


Replies:
Robin,

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
Physics Instructor
Illinois Central College



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