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Safety warning?!!! ;)

Discussion in 'Electronic Basics' started by William J. Beaty, Mar 4, 2004.

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  1. Uncle Al

    Uncle Al Guest

    Why would one fabricate a rare earth dipole magnet as sphere? It's a
    great price for the big one! The obvious thing to do is to order two
    and see how the pair is shipped. Kinda hard to envision a "keeper" to
    lessen field decay/time.
    We as a culture deserve to be destroyed. It would be an act of
    compassion.
     
  2. Dave

    Dave Guest

    because its easier than fabricating a monopole magnet as a sphere?
     
  3. John Larkin

    John Larkin Guest

    The 1.4 megagauss number is absurd; kilogauss, maybe. I seriously
    doubt the part about separating the iron out from one's blood, too;
    superconductive MRI magnets are far more powerful than any PM can ever
    be, and have no such problems. And no small magnet is going to affect
    a color TV from three feet away.

    This guy sounds like a fathead, hardly a humorist.

    John
     
  4. They're also farther away. Inverse cube law, right? But anyway, if I
    remember correctly (which I might not), the magnetic field in MRI is pulsed,
    and is pretty even throughout the cavity, meaning that it shouldn't pull
    things strongly in any particular direction. By contrast, I believe Kevin's
    talking about being within a centimeter of the magnet for a prolonged period
    of time. Obviously, he handles the things himself.
    I shop at his store pretty regularly. There's probably not much point in my
    vouching for him since you don't know me either, but for what it's worth,
    you might want to at least have a conversation with him before labeling him
    as a fathead. In my experience he's not one, at least no more so than most
    of us.
     
  5. Uncle Al

    Uncle Al Guest

    A megagauss is 50 teslas. No way in Hell - not even for a two-stage
    supercon magnet plus a conventional core. The only two ways to get in
    the megagauss region are to either push a whole huge laser capacitor
    bank through a metal loop, flashing it to plasma in the process; or
    cool a pre-stressed armored conventional magnet with a river of high
    pressure water and push a DC powerplant through it (Ritter magnet, but
    not for long).

    The force of magnetic attraction depends on field divergence. Trace
    the field lines of a dipole sphere - wow! It would be a great
    micro-gee experiment for International Space Station Freedom FUBAR
    Space Hole One Alpha. You float two spheres with facing opposing
    poles a fair distance apart and ready your triggered high speed
    camera. They will smash together almost explosively (hopefully
    killing everybody aboard with shrapnel and letting the huge stupid
    expensive worthless nightmare deorbit to its welcome destrucuton).

    Uncle Al has a pair of fair-sized Fe-Nd-B magnets, with a book in
    between. You handle those puppies with great respect and keep the far
    away from computers and TVs. Even a Helmholtz pair of ceramic ferrite
    magnets from a microwave oven are dangerous if you get your flesh in
    the way when they kiss. NEVER allow a pair of magnets like that to
    freely slam together.

    It would be intesting for Oxford Magnets to try hydroponically growing
    seeds in the bore of one of their really high field supercons during
    required shakedown. Photosynthesis is all about charge, hence triplet
    spin, segregation. Twenty teslas on a well-chosen flower would be the
    cat's pajamas: "Consider the lilies of the field, how they grow; they
    toil not, neither do they spin!"
     
  6. John Larkin

    John Larkin Guest

    The patient is *inside* the magnet. Can't get closer than that.
    The gradient fields are pulsed, but they're fairly small. The main Z0
    field is a huge DC superconductive magnet.
    Well, part of your body is outside the field, and part is right in the
    strongest part. That's a hell of a gradient.
    The way you get a blood clot from supermagnets is by letting a pair of
    them snap and pinch you. *That* can really hurt.

    John
     
  7. Eric Gisse

    Eric Gisse Guest

    As it happens, yes.

    A halfhour ago I was using the lamp used for spectroscopy. On the
    housing for the lamp, it says with the standard DANGER sign: Do not
    touch leads while on.

    Thanks for the tip, PASCO. *chuckle*
     
  8. Uncle Al

    Uncle Al Guest

    [snip]

    Make that "Bitter magnet," and then to only 37 teslas.

    http://www.hfml.kun.nl/20t-magnet.html
    http://www.mext.go.jp/english/news/1999/10/s991002.htm

    Uncle Al is sweating the chirality of a Klein bottle's non-orientable
    surface. It's slow going.
     
  9. Dave VanHorn

    Dave VanHorn Guest

    Know of any other good "safety sheets?"

    I have a bottle of Children's cold medicine that states that one shouldn't
    operate any heavy machinery after taking a dose...
     
  10. John Larkin

    John Larkin Guest

    I thought megagauss fields had been made with copper coils pulsed to
    exorbitant currents for milliseconds; is that a Bitter? Something
    about using flywheels and special low-impedance DC generators to
    provide the pulse current. I'll have to look it up.

    Oh, I just hung a cluster of supermagnets on a string, off the edge of
    my desk. The detent action in the Earth's mag field is very
    impressive. If you bring things near it, the deflection of the string
    indicates attraction: $20 bills, some inks, a big old rubber drafting
    eraser, stuff like that show small effects. But I saw no sign of
    attraction to my own flesh; the iron in blood is apparently not
    magnetic.

    So I stand by my "fathead" assessment.

    Agreed on the space station: a useless, boring, leaky, smelly waste of
    a good hunk of a trillion dollars.

    John
     
  11. A pet peeve of mine: Everytime I order a pack of carbide inserts for my
    milling machine I get an MSDS warning about eating or enhaling them.
    Now I can see how they might cause some damage if you cram one up your
    nose but it says nothing about mangling your fingers or flying metal
    chips putting out eyes.
    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  12. Guest

    IIRC, it's because the shape of the sphere compresses the field.
    So you get a very intense field at the poles, but more ordinary
    field strength away from the poles.
    Socks
     
  13. Guest

    Well, some of those are pretty dumb, but some are actually the
    result of translations out of English to some other language,
    then back. For example, the warning not to use the hairdryer
    while sleeping should be not to use it on somebody who is
    sleeping or otherwise unable to communicate the fact that they
    are being burnt. Such as hospital patients still under the
    drugs and so on. See, if you are not conscious, you can't
    tell anybody your head is too damn hot.

    There's other warnings that sound stupid but are the result of
    such translations. For example, persons who are unable to roll
    over on their own, should not use waterbeds. If they wind up
    on the heater and touching bottom, they could be there slowly
    getting cooked and not able to get off the heater. So the
    warning on my waterbed that I should not use it while sleeping
    is amazingly dumb on its face, but really means I should not
    be placed in it if I'm unconscious due to drugs, injury, medical
    condition, etc., but normal sleep is fine.

    Just remember, all your warning is belong to us.
    Socks
     
  14. My sister's barbecue grill has a warning something like "Watch
    children closely while burning."

    --Jeff

    --
    A man, a plan, a cat, a canal - Panama!

    Ho, ho, ho, hee, hee, hee
    and a couple of ha, ha, has;
    That's how we pass the day away,
    in the merry old land of Oz.
     
  15. Uncle Al

    Uncle Al Guest

  16. A uniformly magnetized sphere has the field of a pure dipole.
     
  17. On a Swedish chainsaw, "Do not attempt to stop chain with your hands or
    genitals."
     
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