|MadSci Network: Physics|
Hi Kelly, You've asked my favorite kind of question: specific enough to be able to answer, but vague enough to let me to be able to come up with all sorts of cool science info. So I'll just ramble for a while, and you pick the answer you want. Answer #1: Two. Ferromagnets and... um... not. Ferromagnets are any material that can be permanently magnetized. If you apply a magnetic field, then remove it, some of the domains (small zones in the material) will remain aligned, creating an internal magnetic field. These are the magnets that most people think of when they say magnets. Non Ferromagnetic materials fall into two categories that aren't very different. Paramagnetic and Diamagnetic materials will magnetize while under a magnetic field but it'll go away once the field is removed. Most materials fall into these categories. (They differ because one is from electron orbitals, and the other is from electron spins, but that's a different question.) Note: Any ferromagnetic materials become paramagnetic above their Curie temperature. Answer #2: Two. Rare Earth and Ceramic. The two types of magnets you'll typically find in any science lab or be able to purchase are going to be crumbly ceramic stuff, or a pretty hard metal alloy (rare earth). Answer #3: Two. Permanent or Electrical. Permanent magnets don't require any electricity to run. An electromagnet is a paramagnetic material that produces a magnetic field when electrical current induces one. The effect goes away once the power is off though. Answer #4: Lots. There's Ferrite, Alnico (Aluminum-Nickel-Cobalt), SmCo (Samarium Cobalt), NIB (Neodymium-Iron-Boron), Europium Oxide, Yttrium- Iron-Oxide, Gadolinium, Dysprosium, Manganese-Arsenic, and many others. These differ in their magnetic strength, material strength and brittleness, cost, Curie temperature, and a bunch of other stuff. If you want more specific info on their differences, here is a table of Curie Temperatures; here is a description and rating of different types; and here is a list of frequently asked questions. Other cool links: Magnet University Cool Magnet info, pictures, and extra cool links Analysis of medicinal magnet therapy I hope this helps! Jeff Yap Mad Scientist
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