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dumb battery question

Discussion in 'Electronic Basics' started by Mark-T, Apr 15, 2006.

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  1. Mark-T

    Mark-T Guest

    I was talking to someone about batteries the other day.

    He said when you bring certain metals together, the
    potential appears 'naturally', i.e. merely by the action
    of sandwiching them. I answered that's impossible,
    it would be free energy, entropy contradicts it. It has
    to be charged, after bringing them into proximity.

    Assuming I am correct - that raises the question of
    how the manufacturer charges them up in the first place,
    for the non-rechargeable types.
    e.g. alkaline batteries (what does that mean anyway?)

    Thanks,


    Mark
     
  2. crazy frog

    crazy frog Guest

    chemical reaction of whats between the 2
    metals
     
  3. Don Bruder

    Don Bruder Guest

    You would be wrong in that answer.
    No, it doesn't. And it's not "free". It comes at the cost of one (or
    both) of the metals corroding into something other than "pure whatever
    metal it happens to be". In other words, a chemical change in the
    components yields an electrical potential.
    Incorrect. Various combinations of metals and/or other ingredients start
    producing current immediately upon being brought into contact with each
    other. One example would be a chunk of copper wire and a galvanized
    (zinc-coated) nail stuck in a lemon - The potential is there the instant
    the second strip is jabbed into the lemon, needing only a circuit from
    the wire to the nail to start flowing. No "charging" needed - unless you
    count the assembly process as "charging".

    Pull the wire/nail out after using it to power something for a while,
    and you'll note corrosion on the copper wire, and similar corrosion on
    the nail. That corrosion is indicative of the metals being changed to
    "other-than-pure-metal" compounds as part of the electrochemical
    reaction.

    Right now, I can't name a pair of metals that will create a current if
    brought together all by themselves, but I know that such combinations do
    exist, despite my faulty memory, and I'm sure that others can and will
    name them.
    The process of assembling the components *IS* the charging process. The
    energy is in the chemistry of how the components react with each other.
    Once that chemical reaction has completed (turning the original
    materials, whatever they might be, into "something else") the battery is
    "dead" - No more energy (or at least, no more *USEFUL* energy) can be
    pulled from it - "The gas tank is empty", so to speak.
     
  4. Dan Beck

    Dan Beck Guest

    Hello Don,

    very well written. If one has amalgam fillings in their teeth, and tries
    chewing on aluminum foil, you will feel a "zing" in your teeth, resulting
    from electric current generated much the same way as your lemon/nail/copper
    model does. Please do not ask how I know this...:)

    Regards,
    Dan
     
  5. Chris

    Chris Guest

    Hi, Mark. As Mr. Frog and Mr. Bruder suggested, the battery potential
    is the result of the chemical reaction between metal and electrolyte.

    Your friend may be confusing batteries and thermocouples. A
    thermocouple is the junction of two dissimilar metals, and can produce
    a small temperature-dependent voltage. Note that the potential
    difference produced by a thermocouple isn't a violation of the laws of
    thermodynamics (TANSTAAFL: There Ain't No Such Thing As A Free Lunch)
    because the electrical energy produced by the thermocouple actually is
    converted from thermal energy.

    You might want to look at these:

    http://en.wikipedia.org/wiki/Thermocouple
    http://en.wikipedia.org/wiki/Battery_(electricity)

    Good luck
    Chris
     
  6. Salmon Egg

    Salmon Egg Guest

    Depending upon what you really mean, you are probably wrong. The pair of
    metals can act as a thermocouple unless everything is at the same
    temperature.

    Bill
    -- Ferme le Bush
     
  7. Mark Thorson

    Mark Thorson Guest

    That's how this thing works:

    http://www.phisick.com/a8qbb1.htm
     
  8. Angelo

    Angelo Guest

    Mark-T ha scritto:
    I suspect that perhaps you mean something like
    'contact potential' or 'voltaic potential'. If so, when
    one brings in contact, even at the same T, two samples
    of different metals there's a sudden little flow of current,
    which vanishes almost instantaneously, as a commont
    Fermi level is reached. This leaves a metal with fewer
    electrons than the other, but that imbalance of charges,
    once established, is useless as to produce any further work.
    That resembes the well known example of communicating
    vessels.

    [snip]
    Best regards
    Angelo
     
  9. fkasner

    fkasner Guest

    Yep, finally somebody really answered the question. The phenomenon is
    well known but mistakenly explained in dealing with the transfer of
    electrons associated with "static electricity". The rubbing of one item
    on another is mistaken claiming that friction energy causes the
    transfer. It is the potential differences of the two objects and the
    rubbing is needed because otherwise the contact is not intimate enough
    to allow the process to occur. So there is some small electrical change
    that accompanies intimate contact between two different substances.
    However it is largely negligible.
    FK
     
  10. John Fields

    John Fields Guest

    ---
    You, sir, are an idiot. Perhaps, even, a cretin.

    There was no mention made of rubbing either of the materials with an
    electrophorous, all that was described was bringing dissimilar
    metals in contact with each other, which you didn't address.

    Even so, your description of the mechanism which causes charge to
    accumulate is flawed.
     
  11. crazy frog

    crazy frog Guest

    i see you pick on others to freak.
    and what you are saying im collecting as well.
     
  12. John Fields

    John Fields Guest

    ---
    I like to call a spade a spade, loser.
    ---
    ---
    Why? all you have to do is go to Google groups and search the
    archives to get to the 14000 posts I've made over the last 10 years
    or so.

    But, if what you want to do is rat me out to my USENET provider, go
    here:

    http://www.giganews.com/contact.html

    and fill out the form with your complaint.
    Good luck.
     
  13. fkasner

    fkasner Guest

    I'll no lie down in the mud with you and respond to your ill advised
    descriptive malevolence. However I have demonstrated the electrophorous
    to many a first college physics class. Mere contact produces little
    electron transfer. Some rubbing allows more intimate contact and more
    significant electron transfer. Contact potential differences are quite
    real and explain the transfer of electrons that allow for static
    electricity charges occurring. However if the substances are metals the
    ability to transfer electrons is limited since conduction limits the
    extent of transfer before the objects are separated.

    And you, sir, are not worthy of the term I apply to you.

    FK
     
  14. John Fields

    John Fields Guest

    ---
    Regardless of what you may think of my "descriptive malevolence",
    the fact remains that the topic of the thread was about generating a
    current by merely touching dissimilar metals together. A battery
    with no electrolyte, if you like.

    Your description is that of generating static electricity by rubbing
    a _non-conductor_ with another non-conductor and accumulating unlike
    charges on the two different surfaces, which has absolutely nothing
    to do with the subject being discussed.

    Your apparent inability to understand that, I believe, lends
    credence to my "descriptive malevolence". Wouldn't you agree, if
    the shoe was on the other foot?
    ---
     
  15. crazy frog

    crazy frog Guest

    big deal
     
  16. crazy frog

    crazy frog Guest

    that was not ment for you.
    its for john fields.

     
  17. John Fields

    John Fields Guest

    ---
    What happened to the plonk?

    Just as I thought, you liar, you haven't plonked me at all.
    You're sitting there reading it all, and you don't even have the
    discipline to not reply in order to keep up your pretense.

    You're a worthless loser, frog.
     
  18. Chris

    Chris Guest

    Mr. Fields -- I think we're in one of those "The beatings will continue
    until morale improves" loops.

    Possibly it's a good time to let it go. It obviously doesn't help.

    Cheers
    Chris
     
  19. Gordon

    Gordon Guest

    Where did you acquire these "dumb batteries?" Are they the same
    type as those that killed the Energizer Bunny? That tragedy
    wasn't caused by faulty batteries or dumb batteries. It was
    caused by improper installation of the batteries.
     
  20. Guest

    Good idea. I'm not sure I *want* to know why one would chew aluminum
    foil to begin with...
     
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