dumb battery question

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

Reply to
Mark-T
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chemical reaction of whats between the 2 metals

Reply to
crazy frog

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.

--
Don Bruder - dakidd@sonic.net - If your "From:" address isn\'t on my whitelist,
or the subject of the message doesn\'t contain the exact text "PopperAndShadow"
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Reply to
Don Bruder

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

Reply to
Dan Beck

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:

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Good luck Chris

Reply to
Chris

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

Reply to
Salmon Egg

That's how this thing works:

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Reply to
Mark Thorson

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

Reply to
Angelo

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

Reply to
fkasner

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

There was no mention made of rubbing either of the materials with an
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Reply to
John Fields

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

Reply to
crazy frog

--
I like to call a spade a spade, loser.
Reply to
John Fields

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

Reply to
fkasner

--
Regardless of what you may think of my "descriptive malevolence",
the fact remains that the topic of the thread was about generating a
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Reply to
John Fields

Reply to
crazy frog

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

Reply to
crazy frog

--
What happened to the plonk? 

Just as I thought, you liar, you haven\'t plonked me at all.
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Reply to
John Fields

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

Reply to
Chris

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.

Reply to
Gordon

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

Reply to
onehappymadman

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