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How to generate powerful electric fields in a small space

  1. Oct 13, 2014 #1
    How would you generate extreme electric fields between two small surface area parallel plates.
     
  2. jcsd
  3. Oct 13, 2014 #2

    Baluncore

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    What a simple question.

    What do you consider to be an extreme field?
    How big is a small surface area? what separation? capacitance?
    DC, AC or pulse? What frequency?
    What is between the surfaces? Air, vacuum, SF6 ?

    DC; Cockroft-Walton Generator. http://en.wikipedia.org/wiki/Cockcroft–Walton_generator
    AC; Sinewave LC oscillator.Tesla coil.
    Pulse; Marx impulse generator http://en.wikipedia.org/wiki/Marx_generator
    or switching off an inductor. http://en.wikipedia.org/wiki/Switched-mode_power_supply
     
  4. Oct 13, 2014 #3
    Sorry dc, and stronger than the magnetic field of a small neodynium magnet
     
  5. Oct 13, 2014 #4
    And rubber in between
     
  6. Oct 13, 2014 #5

    Baluncore

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    Magnetic or electric field?
    Why are you wanting to do this?
     
  7. Oct 13, 2014 #6
    I want a tunable electric field to experiment on ferrofluid with. Since it will react to both electric and magnetic fields. I want electric because I haven't seen anyone actually demonstrating its reaction to an electric field. Everyone always demonstrates with magnetic fields.
     
    Last edited: Oct 13, 2014
  8. Oct 14, 2014 #7

    berkeman

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    You will be limited by the breakdown voltage of the material you put between the parallel plates. What is the breakdown E-field strength of your ferrofluid (and any insulating container that you plan to use)?
     
  9. Oct 15, 2014 #8
    Also - most ferofluids would be conductive - correct - you can not support an E field in a conductor.
     
  10. Oct 15, 2014 #9
    I wasn't able to get ferrofluid to conduct because of its oil base
     
  11. Oct 16, 2014 #10
    Generally, after the density of conductive particles trapped in a dielectric exceed a given level becomes conductive.
    With a fluid, particles are free to align and form conducive paths.
     
  12. Oct 17, 2014 #11
    Alkali-free glass is a material for you. In a slowly varying electric fields it has breakdown strenght > 1000 kV/mm
     
  13. Oct 17, 2014 #12
    So if I were to use conductive oil or increase the concentration of nano particles. It should react to a current running through it?
     
  14. Oct 17, 2014 #13

    Baluncore

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    A ferrofluid has very small magnetic particles suspended in an oil base. A surfactant coats the particles to maintain the separation of the particles in suspension.

    The polar electrostatic forces on the surfactant to particle boundary will be overcome at some point by a strong external electric field. At that point the surfactant will cease to function and the fluid will change behaviour.

    Without active surfactant, clumping of particles will be able to take place. The electrical and physical properties of the fluid will change. That change may be reversible if the surfactants are not “electrolysed” by the high voltage field and they are able to return to cover the particle surfaces.
     
  15. Oct 17, 2014 #14

    mfb

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    In setups where it is possible to compare the strength of electric and magnetic fields, strong magnetic fields are often much easier to produce. Even if your ferrofluid is sensitive to electric fields, I would expect that it is hard to see any effect.

    Sharp tips of electrodes close together allow to reach high electric field strengths with a reasonable overall voltage.
     
  16. Oct 17, 2014 #15

    berkeman

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    Is there an advantage to using sharp tips spaced a distance d apart, versus parallel plates a distance d apart? I can see that if you want to vary the strong field at high frequencies, the lower capacitance of the sharp tips will help, but for static fields you should get the same E = V/d, right?
     
  17. Oct 17, 2014 #16

    Baluncore

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    The voltage gradient near sharp tips will be greater, hence corona discharge.
    A similar thing will happen with a ferrofluid, the surfactant may be denatured on particles near the sharp electrode tips.
     
  18. Oct 17, 2014 #17

    mfb

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    Regions of stronger field where your ferrofluid can accumulate and get influenced by the voltage. There are also regions of weaker field, but those can be filled with air.
     
  19. Oct 17, 2014 #18
    Hmm since the electric field would be hard to generate in substantial strength. would it work to use very thin copper wire wrapped around a rubber container and then use the ferrofluid as the equivalent of the iron core in a normal electromagnet? Or is the center of the electromagnet a magnetic dead zone.
     
  20. Oct 17, 2014 #19

    Baluncore

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    The centre of a loop or solenoid has a strong magnetic field. But do you want an electric or magnetic field?
     
  21. Oct 17, 2014 #20
    I wanted an electric field but it sounds like I couldn't get a strong enough field without pumping enough juice through it to induce fusion.
     
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