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Grass Seed and Electric Field Demo

  1. Oct 15, 2010 #1
    I really wasn't sure where to put this thread...so I hope this is okay.

    Anyway, for our class project I am going to build a small box containing oil and grass seeds. After adding a charge, electric field lines will form. That is the basis of the presentation.

    My question comes in the form of building this device. It will need to be clear as it will be used with an overhead projector.

    I am going to build the box out of plexiglass about 5"x8"x0.5". For the probes I was just going to stick thumbtack like objects through one side of the 'glass leaving the head inside the box and the pin sticking out of the box to attatch alligator clips too.

    That's about as far as I am now which brings me to my questions and ultimate point of the thread.

    1. The oil. This will need to be electrically conductive. Where would one find something like that?

    2. What sort of current will I need to generate this field. The unit will portable so I was hoping to be able to use a battery. But I could use a plug with whatever voltage would be required if need be.
  2. jcsd
  3. Oct 16, 2010 #2


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    Hello erok81,

    I've never made such a project. But I'm guessing that the amount of voltage that you would need to make even tiny objects line up in electric field lines would be dangerously large. I'm talking about tens of thousands of volts or so -- enough to kill a person. And it's the voltage that would be important here, not so much the current.

    And for the oil, I'm pretty sure that you would need non-conducting oil. The electric field in a conductor is zero (in static conditions). So if you had conducting oil, it wouldn't show any electric field lines. And due the the large current (I = V/R, where R is very small) it might likely start fire.

    Might I suggest revising your experiment to show magnetic field lines instead? That can be done completely safe and would only require the materials you already have, a bar magnet, and some iron fillings. You could even use an electromagnet if you wanted to.
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