Does magnetic flux itself cause us to feel force?

Discussion in 'Physics' started by nickw1881, Dec 27, 2009.

  1. nickw1881

    Thread Starter Member

    Dec 25, 2009
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    I thought of a question: Does magnetic flux itself cause us to feel force, or is it the h-field generated in magnetically susceptible materials (or a coil of wire) placed near the flux that cause us to feel magnetic forces?

    Is it like how you can only feel the force due to gravity by placing a massive object (capable of generating its own gravitational field) in the earths g-field?

    I once saw a little magnet floating above a superconductor. I know the magnet poles had flux coming out of them. Did the superconductor produce flux back, or was the floating action produced by the interaction of h-fields due to amperes law: force ~ current swirling in the superconductor.

    Does the h-field flow in magnetically conductive materials the way that flux does? When I see iron filings arranged around a magnet, are they arranged so from the lines of flux, or according to the magnetic force field lines?
     
  2. Wendy

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    We are slightly dimagnetic, which is to say we are repelled by magnetic force. It is so small we don't notice it, except in really, really extreme conditions. The kind of conditions most of use will go our whole lives not experiencing.

    There is no relation between magnetism and gravity that I know of.

    A superconductor will not let a magnetic field penetrate it, it therefore repels magnets.
     
  3. Papabravo

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    Feb 24, 2006
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    The TOE or Theory of Everything is looking for connections among the four fundamental forces. There are some tantalizing reasons for wanting to connect gravity to the the electomagnetic, weak, and strong forces. The Wiki is a good place to start on this mind bender.

    http://en.wikipedia.org/wiki/Theory_of_everything
     
  4. studiot

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    Nov 9, 2007
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    Really depends what you mean by 'feel'.

    Certain molecules in our bodies respond to impressed magnetic forces. This is the basis of magnetic scanning technology used in medicine, chemistry and other disciplines. Do a search on Nuclear Magnetic Resonance (NMR).
     
  5. bertus

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  6. rjenkins

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    Bit of a trick question?

    People have mass and directly experience their own weight due to gravity.

    People are not particularly magnetic, so most experience is from playing with magnets and discovering how they attract iron & other magnets etc.

    Magentic 'lines of force' are convenient for explanations, but not real; think of lines on a map showing altitude, they are for our convenience and do not exist on the real hillside. Likewise, magnetic field strength changes smoothly with distance.

    The apparent lines given with iron filings are due to the induced magnetism in each iron particle, causing them to attract end to end and repel side to side.
     
    Last edited: Jan 8, 2010
  7. studiot

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    Not really.

    Birds navigate by way of a centre in their brains that is sensitive to the earth's magnetic field.
     
  8. MarkTBSc

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    Feb 27, 2010
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    Everything that has Mass exerts a gravitational force on everything else that has mass in the universe. You feel gravity because the Mass that is the Earth is exerting a gravitational attraction on you, but at the same time you are exerting a gravitational attraction on the Earth... As well as Alpha Centauri, all the stars of the Whirlpool Galaxy and the outermost speck of dust on the outer fringe of existence.

    Having said that, some scientists are now saying that gravity is just an effect of the Information diffusion gradient. When they start talking about stuff like that I go lay down in the dark.

    The magnet over the superconductor is a matter of the magnetic fields of the magnet inducing eddy currents in the superconductor which are in opposition to the fields of the magnet, creating levitation. There are some fun things you can do with MRI machines and Aluminium plates in that vein.

    I work around a 3T magnet and I've never felt it pull on me. Putting your head at the end of the magnet's central bore and moving it around aggressively can cause feelings of dizziness and disorientation. 7T is the strongest field human beings are recommended to be exposed to, although Siemens apparently has a magnet that goes up to something like 65T. Above 10T or so you start seeing neural induction effects from the field.
     
  9. BillO

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    Nov 24, 2008
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    Holy gonads Batman, R U serious?
     
  10. KL7AJ

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    Nov 4, 2008
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    The only time I was ever able to feel a magnetic field directly was during a tour of the Alcoa aluminum smelting plant. They have cables carrying tens of thousands of amperes through them, because aluminum must be electrically smelted...or it vaporized.

    I asked the plant guide, if it was my imagination, or could I actually feel something in my ankles (the cables were a few inches off the floor). He said, "yep..there's enough current to magnetize the iron in your blood cells. Perfectly harmless..but perfectly creepy, anyway. :) "

    Eric
     
  11. MarkTBSc

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    Feb 27, 2010
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    That's what I was told when we were installing our MRI, and that was four years ago so they may have something even beefier now.
     
  12. bertus

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  13. b.shahvir

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    I like your signature though!! ;)
     
  14. someonesdad

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    Interesting, Mark -- I fiddled with a 1 T magnet a few decades ago and, while it's easy to see eddy currents in metals, never could feel any effect on fingers or hands going between the pole pieces.

    I have a "fond" memory (a better name would be "lesson") from when I was a student. We were doing some experiment and needed some special pole pieces for the magnet. I went to the local supply place and came back with a 12" long chunk of 4" diameter round steel bar stock. I had to cut this material off into two pole pieces so I could machine them to the special shape required and the only tool to do this was the old lathe in the shop. Since I had some minor experience with a lathe, I thought I'd just use a cutoff tool and chop it off. No sweat, right? Ha! I chucked it up in the 4 jaw and center drilled it, then held the piece on a dead center and started feeding the cutoff tool in. Not only did I break the cutoff tool off in the work, I didn't know that I should lubricate the dead center (I had used a live center before) and a bit into the job was surprised to see a bright, molten drop of metal fall into the ways. Yep, I melted the tip off the center!
     
  15. Markd77

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  16. Duane P Wetick

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    Apr 23, 2009
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    The electron spins in ALL elements are influenced by strong magnetic fields. As you have probably surmised, certain elements have more electron spins than others. Iron (fe) has the most spins for its cost compared to other elements, so it is a natural candidate to make a magnetic circuit. Does this help?

    Cheers, DPW [ Everything has limitations...and I hate limitations.]
     
  17. bertus

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    Apr 5, 2008
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    Hello,

    About the elements that react on a magnetic field.
    C12 (carbon with mass 12) does not react (it has no spin).
    C13 (carbon with mass 13) willreact on the magnetic field (it has spin).

    Here is a little bit more info:
    http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/nmr1.htm

    Also each element has an other frequency depending on the fieldstrength.

    Bertus
     
  18. Wendy

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    Mar 24, 2008
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    Sounds like a good way to make cheap heavy water. I'm sure it has been exploited if so.
     
  19. bertus

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