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Low Level EMF and Helmholtz coil design

  1. Jul 14, 2016 #1
    The problem statement:
    I want to produce an LL-EMF of a specific amplitude and frequency in a pair of Helmholtz coils of pre determined radius.

    The frequency and amplitude are derived from the following equations from this publication http://www.heartrhythmjournal.com/article/S1547-5271(14)01477-5/pdf

    Relevant equations:
    I have put the powers of 10 in brackets
    Equations derived by Jerry Jacobson, DMD,PhD

    1) mc(2) = q(j) v B L
    where m =target molecule mass = for vasostatin-1 mol weight of 7KD = 7000 x 1.169 x 10(-24)gm
    c =velocity of light =2.99 x 10(10)cm/sec
    q(j) = 1 ab-coulomb
    v = earth's orbital velocity = 3 x 10(6)cm/sec
    L =target linear dimension = 1.73 x 10(2)cm
    B =magnetic amplitude in Gauss

    2)Based on the aforementioned assumptions and hypotheses, Jacobson then
    proposed the desired frequency of the applied electromagnetic field by invoking the
    cyclotron resonance equation:
    f = qB/2(pi)m
    where B =magnetic amplitude in Gauss (derived from above equation)
    q =normalized charge of electron = 1.602 x10(-19) ab-coulomb
    m =norm. mass of electron = 9.1095 x10(-28)

    My work so far:
    I have worked them through for a human size of 1.73 meters, and get the results as :
    B (amplitude in Gauss) = 2.01 x 10(-8)G
    f (frequency in Hertz) = 0.56Hz
    I can scan and upload my longhand work if needed.

    So then to design the Helmholtz coils. Their size should be suitable to centre the magnetic field on the heart area of a human, giving a radius of 35cm (Radius of coils equals distance of separation).
    The magnetic flux density at their midpoint is given by:
    B =(4/5)(3/2)UnI/R
    here U =4PI x 10(-7) T.m/A (permeability of free space)
    n = number of turns in each coil
    I =current in amps =2.5amps (see below)
    R =radius in meters =3.5 x10(-1)
    B =derived as above =2.01 x 10(-8)G

    I have a frequency generator that outputs 20V p-p maximum, output impedance is 50Ohms, so current should be 2.5 amps

    However, when i try to solve the above equation to get the number of turns for the coils, i get 2.37 x10(-3) turns!
    Am i using the correct equations?
    Last edited by a moderator: Jul 14, 2016
  2. jcsd
  3. Jul 14, 2016 #2


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    Do you really want to targtet one (1) molecule ?

    Earth magnetic field is about .5 Gauss, so wouldn't it be a lot easier and cheaper to just slowly pirouette ?
  4. Jul 14, 2016 #3
    Thanks BvU,
    I am blindly following the original paper as they had success suppressing fibrillation in dog's hearts by targeting that particular molecule. Are you suggesting to scan through the frequencies when you say pirouette?
  5. Jul 14, 2016 #4


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    No I mean you rotate physically. Like a ballerina. Slowly. One revolution in ##1 \over 0.56 ## sec. A field of around 0.5 Gauss (depending on orientation) goes through one period in that 0.56 sec. Probably not very helpful, though.

    What I mean to say is that ##10^{-8} ## Gauss is excruciatingly small. (Big physics experiments work with several Tesla (1T = 10000 Gauss).
    There must be something awry there, but I don't have access to the original article.

    [edit] if your target mass is on a molecular scale, shouldn't the target length be on such a scale too ? :smile:

    PS your ' 2.4 ##10^{-3}## ' turns at 25 A give the 'same' field as 2.4 turns at 25 mA
  6. Jul 15, 2016 #5

    Yes, understood, a nice idea!

    It seems that low level emfs do actually have quite an effect, as the paper i referred to has found. Here is some background:
    Maybe i am approaching this from the wrong direction. Is there a standard number of turns and wire size used when winding a pair of Helmholtz coils? Perhaps i should use that and then vary the current to produce the required field strength.
    I would really like someone to check the results of the 2 initial equations though. Any takers?
    P.S. I have a copy of the manuscript referred to that i originally downloaded. It seems now that a registration or fee is required to view it. Would i be breaking copyright to post a link to my own copy?
  7. Jul 15, 2016 #6


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    In physics school labs, Helmholtz coils are used in the Thomson e/m experiment (google e/m experiment or e/m apparatus !) Typically 100 turns, and a few A. A bit smaller than what you intended (but do you really want these EMF influences in a large volume if they have such effects ? -- in post 1 you seem to think of a centered field (do you mean focused, concentrated, localized ?), but Helmholtz coils are popular because they generate a fairly uniform field )

    In your link they mention 2000 Gauss - a long way from ##10^{-8}## !

    You mean other checkers ?
    I pointed at target molecule for m and target length for L.
    I could also ask: what on earth has the earth orbital velocity to do here ?
    And what can possibly have 1 ab-coulomb (do me a favor: use Coulomb) charge ? It is gigantic.

    I don't understand the expression. All I can do is check dimensions -- they seem to match. And read the source -- which I can't.
    But it sure looks weird. ##mc^2## is energy. ##qvB## is a force -- but a force perpendicular to v. So ##qvBL## has the same dimension as ## mc^2##

    In short: I don't believe for a moment this is is right.
    If I were you I'd forget this Jerry Jacobson altogether.

    Copyrights ? I have no idea. Read the small print perhaps ? But you could retype the relevant passage, I am pretty sure.
  8. Jul 15, 2016 #7

    jim mcnamara

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    Interesting. Jacobson (a dentist BTW) has one publication. That I can find. He has two patents on the use of low-level EMF on various maladies. All patents issued prior to the publication which came out in 2001.
    @BvU I would second your opinion. At best, the publication listed here appears to be a limited clinical trial. And it seems to be applying a magnetic field for osteoarthritic problems.

    BTW - the last patent seems 'interesting' - a cure for aging.

    Lest you think I'm being silly, consider:
    US Podiatrists sometimes use a strong magnet for 24 hours after foot surgery on a diabetic patient, to
    speed healing. But this is based purely on clinical observations. Note the word 'strong' and the fact that the magnet is in very close proximity to the wound.
    Last edited: Jul 15, 2016
  9. Jul 15, 2016 #8
    Thanks for your interesting responses, and for taking the time to think about this.
    Here is a link to the paper i referred to
    As it was published in the medical literature I thought it was legit. Do you think its all bullology?
    As a sufferer of AFib myself, i tend to clutch at any straw like the drowning man!
    P.S. @BvU, thanks i didn't realize that you had worked through the results i obtained
  10. Jul 15, 2016 #9


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    Great. The link shows you faithfully reproduced JJ's 'writing' on p19. Interesting is that his ref 19 (surprise: by JJ!) is also available on the net. For convenience he there rewrites three hundred years of physics development for his purposes and has no problem equating coulombs to kilograms: 1 coulomb is 6e18 electron charges, one electron is 1e-30 kg, so clearly 1 coulomb is 6e-12 kg. And so on. I don't believe my eyes.
  11. Jul 15, 2016 #10
    Ok BvU, well it seems I have wasted your time.
    It shows how easily I can be baffled both by accepting published science papers, and by my limited understanding. Result: a couple of coils and a frequency generator ain't going to fix my arrythmia!
    Still, many thanks for your advice.
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