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Making a voltaic pile with Euro coins

  1. Aug 22, 2010 #1
    Can it be done? I tried stacking cells made with 1€ coins + 50c coins separated by some tissue soaked in sea salt but didn't measure any voltage with the multimeter.

    The problem is every coin except the brown ones consist mainly of copper and the brown ones are steel plated with copper. Heres the composition of Euro coins:

    1c, 2c and 5c: Copper plated steel
    10c, 20c and 50c: 89% copper, 5% aluminium, 5% zinc, 1% tin
    Centre of 1€ and ring of 2€: 75% copper, 25% nickel
    Centre of 2€ and ring of 1€: 75% copper, 20% zinc, 5% nickel

    Steel is mainly iron but the brown coins are plated with silver so it doesn't matter what the core is made of does it? My inspiration for making a voltaic pile came after watching an episode of Breaking Bad where the battery of their caravan goes dead out in the desert and they manage to get it started with a voltaic pile made from change. You'd probably need a pile the height of a house to get 12V but I like the idea of being able to produce voltage with coins all the same.
     
  2. jcsd
  3. Aug 25, 2010 #2
    The problem, as I understand it, has nothing to do with the composition of your coin electrodes, but rather with the connections between each cell and the solutions used for each half reaction. You can get some respectable voltages with those metals but you also need solutions of the corresponding ions. Sea salt is just about the poorest choice!
     
  4. Aug 26, 2010 #3

    Borek

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    It is possible to get decent voltage just from two nails (copper/iron) put into a lemon. My bet is that € coins are a bad choice, I would first throw away those two colored. Note that it doesn't matter what is inside, what matters is what is in contact with the electrolyte - so even if there is iron inside, but plated with copper, this still counts as copper electrode.

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  5. Aug 26, 2010 #4

    Integral

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    I have found that graphite (very thick mechanical pencil lead) and zn work pretty well as electrodes.

    Salt water can work as an electrolyte but I immersed the electrodes in a container full of it. It is not clear to me that you will get much ion mobility in just wet paper.
     
  6. Aug 26, 2010 #5

    Borek

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    Original Volta pile was made with pieces of metal separated by cloth soaked in brine. Ion mobility is not that important when you need just voltage, but obviously high internal resistance will not let you get a decent current.

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    methods
     
  7. Aug 27, 2010 #6
    Wait, how can a voltaic cell work on simple brine if one of the reactants in the net ionic equation is an ion of an electrode metal?
     
  8. Aug 27, 2010 #7

    Borek

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    Ask Volta :wink:

    When there no ions potential of the half cell (as given by the Nernst equation) is infinite. That's a pretty strong impulse to oxidize some of the metal in the presence of any (even weak) oxidizing agent.

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  9. Aug 28, 2010 #8
    OH! I remember Nernst now! It will make a voltage, but a terribly weak one. Thanks.
     
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