Leyden jar

Discussion in 'The Projects Forum' started by CrazyAl, Sep 19, 2010.

  1. CrazyAl

    Thread Starter New Member

    Aug 27, 2010
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    Hi, I have made a simple Leyden jar out of some foil and a plastic container but the problem is it will not charge.

    I must be missing something very obvious as they are so simple to make, do I need to attach the outer foil plate to the ground (as In outside with a wire connect to a pole that goes into the earth) or does that not matter. Using a multimeter it reads 0.22nf of capacitance (does this need to be higher?).

    Here is some pictures of it

    CIMG6780.jpg

    CIMG6781.jpg

    CIMG6784.jpg

    I have tried rubbing a PVC pipe with a towel by it and made sure the pipe touched the screw on the lid but even when I move the spark gap wire closer or touch both plates nothing happens.

    Thanks:)
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Foil on the outside of the jar for easy contact, and electrode on the inside. I'm not too sure about the plastic lid either. A classic Leyden Jar used a large rubber stopper with a hole in the middle.

    Want to charge it? I ran into this not too long ago...

    Water Battery?
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    What kind of plastic is it. Some plastics use conductive compounds in their manufacture and won't hold much charge above 500 volts. They discharge themselves very quickly in other words. Try it with a large GLASS mayonnaise jar, or pickle jar.

    Environment can also be detrimental to charge accumulation. High humidity for example will discharge a high voltage in just a few minutes even if left standing on a glass plate with insulated standoffs underneath

    A glass rod and a fur coat are good generators of static
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Laboratory glass jars and the rubber stoppers are the classic materials. Both glass and rubber are really good insulators, which is critical for high voltages. The actual capacitance is very low.
     
  5. CrazyAl

    Thread Starter New Member

    Aug 27, 2010
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    Thanks for the replys, I have tried using a glass jar but that made no difference. I have also tried using water and salt inside of the jar but that made no difference.

    Do I need to connect the outside plate to the ground?

    Thanks.
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    No.. You DONT want to ground the charge you are trying to collect.
     
  7. bertus

    Administrator

    Apr 5, 2008
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  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    People have made these for about two hundred years now.

    They can kill you if they are big enough and have a high enough charge on them, and yes the outer surface can be connected to earth. The inner surface is the one you charge.

    coat the outer surface with shellac and leave a small portion of the bottom of the foil uncoated for the connection to ground. Set the jar on a glass plate and put the plate on top of several layers of wax paper and then set the works on a WOOD table top or chair.

    Go to www.books.google.com and use advanced search to get full view returns only then search for Make a Leyden jar.
     
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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    A capacitor won't charge unless it can generate a potential between two plates. Without grounding the outer plate it can charge up with respect to the air around it but I'd try hooking the outer foil up to something - either ground or a conductor of much larger area.
     
  10. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    I have forgotten these things exist.

    Boy am I going to have some fun on the weekend.
     
  11. CrazyAl

    Thread Starter New Member

    Aug 27, 2010
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    Sorry I have not replied, as most of you probably know life gets in the way of our little projects :mad:

    I managed to instead of using a jar to wrap the foil around find some laminated pieces of paper and stick larger pieces of foil to each side of them and it seems to hold a bit of a charge from my "hacked/modded bug zapper that puts out around 1600volts. Heck as I was putting it away at least a few minutes after I last "discharged" it and got a bit of a shock!, thankfully according to my multimeter it only has a capacitance 1.5-2nF so I didn't experience any burns!
     
    Last edited: Sep 28, 2010
  12. ELECTRONERD

    Senior Member

    May 26, 2009
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    I made a couple of these years ago, they are a lot of fun.

    To charge it adequately you can try turning on a TV with a CRT and run it across the screen, but try not to touch it directly. Listen for a crackling-pop kind of noise, which will indicate that it is charging. The resulting shock that you'll get when you touch the inner ternimal won't be very large, so if you want a greater shock you should try a plastic slide. The latter arrangment involves going down the slide till you reach the end. Try not to touch the ground though, as it will lead to ground. Then stand up and run the leyden jar capacitor all over the surface of the slide, storing the electrostatic energy. You should get a substantial shock from that, slightly larger than with the TV.
     
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