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Answers to many Frequently Asked Questions on magnets and magnetism.



1. What are Rare Earth Magnets?
 Rare Earth magnets are magnets that are made out of the Rare Earth group of elements. The most common Rare Earth magnets are the Neodymium-Iron-Boron and Samarium Cobalt types.
2 What are the different types of magnets available?
There are 2 types of magnets: permanent magnets and electro-magnets.
Permanent magnets emit a magnetic field without the need for any external source of power. Electro-magnets require electricity in order to behave as a magnet.
There are various different types of permanent magnet materials, each with their own unique characteristics. Each different material has a family of grades that have properties slightly different from each other, though based on the same composition.
3.What Br, BH(max) and Hc mean?
Remanence Br: Determines the pull of magnet, the larger the Remanence the stronger the pull.
Energy product BH(max): determines the amount of magnetic material need for one design, The bigger the energy product is, the smaller the size of the magnet you need.
Coercivity Hc: The larger the coercivity, the stronger is the magnet's resistance to demagnetization.
4. How permanent is a magnet's strength?
Generally the magnet will experience a degradation in its physical properties, such as corrosion, prior to it demagnetizing because of age. However, If a magnet is stored away from power lines, other magnets, high temperatures, and other factors that adversely affect the magnet, it will retain its magnetism essentially forever.
5. Will magnets lose their power over time?
Modern magnet materials do lose a very small fraction of their magnetism over time. For Samarium Cobalt materials, for example, this has been shown to be less that 1% over a period of ten years.
6. What might affect a magnet's strength?
The factors can affect a magnet's strength:
a. Heat
b. Radiation
c. Strong electrical currents in close proximity to the magnet
d. Other magnets in close proximity to the magnet
e. Neo magnets will corrode in high humidity environments unless they have a protective coating.
Shock and vibration do not affect modern magnet materials, unless sufficient to physically damage the material.
7. Can a magnet that has lost its magnetism be re-magnetized?
Provided that the material has not been damaged by extreme heat, the magnet can be re-magnetized back to its original strength.