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What type of a magnet is really strong, not too big, durable, . . .

  1. Dec 16, 2006 #1
    What type of a magnet is really strong, not too big, durable, and has a long life? Where do I get it?
  2. jcsd
  3. Dec 16, 2006 #2
    How big? Do you mean small like cell phone size, or small like a penny?
  4. Dec 16, 2006 #3
  5. Dec 16, 2006 #4


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    Neodymium magents are awesome. They're so powerful they're like no magnet I've ever experienced.
  6. Dec 16, 2006 #5
    My old school had a 7T superconducting niobium magnet in liquid helium! Although they never did let me play with it. :grumpy:
  7. Dec 17, 2006 #6


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    They're not that durable. One of my friends dropped one of MINE on the ground and it exploded into five pieces that all sucked themselves right back together from the magentism.
  8. Dec 17, 2006 #7
    I need one which is no bigger than around 4 inches in every dimension. And I need one which is easily available, not rare.
    it doesn't have to be really durable you know, but durable yes it should be.
    Last edited: Dec 17, 2006
  9. Dec 17, 2006 #8


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    "Rare" earth magnets are not rare.

    You need to be specific with your questions. The magnets I work with are 10-16T magnets that weigh from 100-200 lbs. But they're very delicate. As far as I'm concerned, a strong and light magnet would be something giving me more than 15T at less than 100lbs. I'm guessing that's not what you want. On the other hand, for an NdFeB magnet, a 4" cube is GIANT!

    That's why numbers are important! Descriptors like 'strong' and 'small' are too unspecific to be useful. What do you want to use the magnet for?
    Last edited: Dec 17, 2006
  10. Dec 17, 2006 #9
    "Rare-earth" magnets refer to the "rare-earth" elements used in them, which are not "rare" at all:


    Permament magnets "last" forever, unless you roast them in an oven. The neodymium magnets listed on the United Nuclear page are basically the strongest magnets you can get; they are potentially dangerous. They are not durable though, quite brittle. You can buy them for a few bucks, or pull one out of a broken hard drive (watch out for sharp metal edges!).
  11. Dec 18, 2006 #10
    I need a light weight magnet, which has to be strong because it will be lifting quite a lot of weight, More than 30 KG probably(i don't know maybe 60kg!) that's why I"ll probably use 4 of them for more power.

    But what I want is not this magnet to be the stronger one...
    I want to use it in this way:
    There will be an electromagnet.... around 12 inches away, and when I turn it on it is supposed to pull this magnet, and there would be a rubber ring in between so they won't smash together... alignment etc. will not be considered atm. This permanent, which I need, would pull maybe 5 -I don't know how much 50(?)KG. I haven't estimated that yet. And I'm sorry that I am not much familiar with Telsa, so I can't give you an estimate in how much T i need. I know I'll need to study it before I continue, so I'll familiarize myself with all this after my exams finish.
    So atm, I can just talk in childish language and say I need to pick up this many weight.
    Anyway getting back to the point. Where was I? Yeah so the electromagnet would be the one pulling the weight and that has to be the one which is really strong... And I'll attach a potentiometer, so the I can regulate the strength of the electromagnet. How strong does the electromagnet have to be, what voltage should I supply? I don't know yet. I"ll have to figure that out as well. So this permanent magnet which I need is not supposed to be the stronger one. It just needs to be able to be able to pick up all that weight and go towards the electromagnet.
    And why I need to regulate the electromagnet's strength? That's so I could change the speed with which the permanent magnet moves towards the electromagnet.
    So you see, there's a chance that the rare neodymium magnet will crack under all that weight. And I don't want the permanent magnet to be too strong creating magnetic fields that might interfere in other things.

    Thanks a lot.

    EDIT: thnx for telling me about rare earth magnets :). Silly me.
    Last edited: Dec 18, 2006
  12. Dec 19, 2006 #11


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    These two things are about as opposing as you can get... Factor in a few hundred kg of soft iron shielding to your device.

    BTW, you do realize that the electromagnets are going to have the same magnetic fieldmproblems as your perm magnets?
  13. Dec 20, 2006 #12
    Yeah, I do, and I know I have to do something about it. Still an electromagnet can be turned off. So that's not as big a problem.
    But what about the magnet. What if stick a neodymium magnet in an iron casing. In this way, the magnet would be protected, but would it still be as strong? Because if a neodymium magnet is the strongest, then I think that would be needed.
    Plus I think an iron casing would be essential in anymagnet.
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