Electromagnetism and Water

Discussion in 'Physics' started by Magnosurfer, Jun 9, 2008.

  1. Magnosurfer

    Thread Starter New Member

    Jun 9, 2008
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    TO ANYONE READING THIS. I've got a theory and if you could help me out I'd appreciate it.

    Water being a bipolar molecule, that is slightly positive at the hydrogen side and slightly negative at the oxygen side, could then be referred to as a permanent magnet could it not?

    Also is water surface tension or the air-water interface a specific charge, for instance slightly negative, by virtue of the alignment of water molecules at the surface?

    One more thing, does water react to a magnetic field? Clearly tides are caused by the gravitational effect of the moon, but how about a water molecule in the presence of a magnetic field??

    Thanks in advance for any help on these questions
     
    Last edited: Jun 9, 2008
  2. Dave

    Retired Moderator

    Nov 17, 2003
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    It would be classed as a permanent dipole which has a dipole moment due to the electron distribution between the H and O.

    Water is classed as diamagnetic, therefore it has a small repulsive response to an applied magnetic field - more specifically the molecule acquires a small induced magnetic moment (Faraday's Law - B-field induces E-field, creates induced magnetic moment) that opposes the applied magnetic field.

    Dave
     
  3. Magnosurfer

    Thread Starter New Member

    Jun 9, 2008
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    Thanks Dave. I'm not very well informed on the numerous scientific names describing characteristics and actions etc. nor mathematical formulae.

    That being said, how would a permanent dipole differ from a permanent magnet in its functioning for instance? Also what do you mean by magnetic moment?

    So if I'm not mistaken water being diamagnetic would mean it repels a magnetic field. Apologies for my general lack of knowledge on these terminologies.
     
  4. omnispace

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    Jul 25, 2007
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    Dipole means electric polarization, magnets have magnetic moment/polarization.
     
  5. thingmaker3

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    You are not mistaken. The magnitude of such repulsive force is quite tiny. Almost all substances are diamagnetic.
     
  6. Dave

    Retired Moderator

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    Structurally the permanent magnet will produce a magnetic field emanating from the poles, the permanent dipole will produce a electric-field emanating from the poles. The permanent magnet is a magnetic dipole as opposed to the water molecule which is an electric dipole.

    See magnetic moment.

    Taking the idea further, if you were to have a series of electric dipoles that when grouped together constructively created a material which had a net electric polarisation across the material, you would have something known as an electrotet, which is the electrostatic equivalent of the permanent magnet. With water this would not happen because the molecules assume a random orientation which results in a neutral electric polarisation across the material.

    You are correct.

    Dave
     
  7. Magnosurfer

    Thread Starter New Member

    Jun 9, 2008
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    Thanks everyone for your insight.
    So dave would not the electrotet phenomen apply to the water surface if water surface tension is the result of alignment of dipolarization within neighboring water molecules to some depth below the surface before random orientation resumes? In other words, at the surface of any water body, random molecular positioning would not occur but would be aligned which could result in the surface being overall constructively polarized - effectively acting as a electric dipole or interchangeably, a permanent magnet?

    I'm quite unsure as to how electric dipoles, though differing from magnetic dipoles, are really different but perhaps just the same thing produced from opposing yet inextricably combined actions?
     
    Last edited: Jun 10, 2008
  8. cumesoftware

    Senior Member

    Apr 27, 2007
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    Water is dipolar, as you said. But the dipolar moment of the water doesn't cause magnetic attraction or repulsion: it causes electrostatic attraction between the molecules of water or other molecular dipoles, either permanent or induced dipoles.

    Now it is proven that the water is slightly paramagnetic, but that is caused solely by the paramagnetism of oxygen. Like iron, oxygen is paramagnetic. Since the oxygen atom in a water molecule tends to attract the electrons from the adjacent hydrogen atoms, but doesn't attract them completely, the electronic pairs of the oxygen valence shell will not always be complete (but most of the time will). The impaired electrons will present spin, causing the paramagnetism of water. The electrostatic attraction cause the water molecules to be oriented so the oxygen atoms will not interfere with each other, preserving the paramagnetic property. Remember that dipolar attraction of water molecules results in interactions between oxygen atoms and hydrogen atoms of nearby molecules.
     
  9. Dave

    Retired Moderator

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    I cannot see why the surface tension would create a structured polarisation of the water, I will have a look into water surface tension and post back with a more detailed view later.

    Water is diamagnetic, note that its magnetic susceptibility is negative by virtue of its relative permeability being (slightly) less than 1.

    Dave
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    There is a classic demo to show that water is affected by static electrical fields - you comb you hair on a winter day and hold the charged comb close to a thin stream of water from the tap. The stream will be deflected some distance.
     
  11. Magnosurfer

    Thread Starter New Member

    Jun 9, 2008
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    This is probably a question arising out of ignorance, but what is the difference between electrostatic attraction and magnetic attraction? The 2 hydrogen atoms and oxygen atom making up the water molecule have no available electrons in a body of water but are orientated with respect to each other, H end of one molecule to the O end of another because of this electrostatic "field"?

    Doesn't every charged particle have a field of its own?
     
  12. cumesoftware

    Senior Member

    Apr 27, 2007
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    You are free to ask. Asking doesn't reveal ignorance, much the opposite.

    Electrostatic attraction refers to attraction due to a difference of electrical charge. Think it like a charged glass rod attracting pieces of paper.

    Magnetic attraction exists only between paramagnetic substances, having each one a permanent magnetic field (two magnets), or having one a permanent field while the other has an induced magnetic field, being this field induced by the first (a magnet and a piece of iron). This behaviour much resembles the electrostatic dipoles I've mentioned in a post before, but the cause and the effect of the phenomena are not the same.
     
  13. triggernum5

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    May 4, 2008
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    Another thing to note is that moving charge creates a magnetic field.. The magnetic field/force is perpendicular the the electric field/force..
    So moving charge (current) creates a change in the magnetic field, and a changing magnetic field can move charge..
     
  14. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I didn't catch the 'theory' you are working on, but I suggest you look up Van der Waals forces (in water)

    They play a very very important role in the physical chemistry of water and in the ultimate allow life on earth.

    http://www.physlink.com/Education/AskExperts/ae206.cfm
     
  15. theamber

    Active Member

    Jun 13, 2008
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    He said he has a theory. First a theory is a general proposition use as a principal of an explanation of certain phenomena. A hypothesis is an untested idea or opinion. Most likely you have a hypothesis that you want to prove in order to escalate to a theory.
    And in mathematics a theorem is something to be proved from other formulas.
    I don't get exactly what is what you want to prove.
    What I could get is that you want to asociate the charges in water with an electro-magnet.
    There are two kinds of magnetic sources. 1. motion of electric charges such as electric currents and 2 intrinsic magnetism of particles inside the atoms.
    You should start with the second.
    Water is a covalent bond there is a chemical bonding present inside the molecule therefore you need to study quantum chemistry to understand the molecular orbitals of water.
    Covalent bonds hold atoms together therefore the atoms of the molecule must share electrons it is a strong bond so it will need a catalyst to be broken down. You may want to check the self-ionization (e.g. the Ph of water). I think it is extremely complicated if you mix the two without understanding one fist.
    Continue your work and let us know what is new, good luck.
    We can only perceive certain facts through our limited senses which do not mean a fraction of what it is out there.
     
  16. KL7AJ

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    Nov 4, 2008
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    Hmmmmm...now that makes one wonder....if one were to freeze a glass of water in a very strong magnetic field, would you have a magetized ice cube?

    :)

    eric

    (I guess I'll have to try it and see, eh?)
     
  17. triggernum5

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    May 4, 2008
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    Its a catch-22, if you could magnetically overcome the H-bonding to make the water exhibit magnetic field then the H-bonds wouldn't be there to freeze the water..
    The H-bonds grossly out match water's magnetic dipole..
     
  18. bertus

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  19. triggernum5

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    But NMR is a probability based situation.. Not nearly every particle undergoes transition, and a magnet with maybe 10ppm oriented isn't much of a magnet..
     
  20. Dave

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    Nov 17, 2003
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    In many cases yes, in some cases no: http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4428303

    Can you get IEEE publications?

    Dave
     
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