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Homework Help: Dielectric constant for a plastic kitchen bag?

  1. Feb 25, 2004 #1

    I'm making some home-made capacitors for an up-coming lab, and I was thinking of using Market Basket/DeMoulas' plastic kitchen bags as a dielectric. I'm really hoping to use it because the packaging info includes the thickness of the bag (19 micrometers), which should increase the accuracy of my results.

    However, I'm at a loss to how to find its dielectric constant. The packaging info says:

    "These bags are made in layers of specially formulated plastic with added strength and stretch for puncture and tear resistance."

    I've seen websites that approximate garbage bags' dielectric constants using polyethylene. Would that be appropriate in this case?

    Is it worth having an approximated dielectric constant in return for a more accurate depth measurement? Or am I better off using something like paper, and measuring the thickness myself? (I don't have any good equipment for that. I'll have to stack the papers, measure that and divide.)
  2. jcsd
  3. Feb 25, 2004 #2
    This is just conjecture on my part, but I imagine there is just as much margin of error in the nominal thickness of those bags as there would be in your measurement. Maybe even more. I saw plastic bags being manufactured once. They basically squirted a stream of molten plastic upward & used a vertical column of forced air to hold it in a cylindrical shape & keep it moving upward until it dried near the ceiling. I don't think you can count on the thickness being perfectly uniform. Paper, I think, is rolled out under pressure, so I would expect its thickness to be more consistent.
  4. Feb 25, 2004 #3
    All right. Thanks for the info!
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