From: hal@finney.org
Date: Tue Dec 11 2001 - 19:13:40 MST
Dossy writes:
> The question is, if I peed into my urine-powered clock before
> I went to bed every night, would it provide enough power so that
> it would keep good time when I woke up 8 hours later?
Actually the liquid just supplies a conductive electrolyte and is
not the source of the energy. A salt solution will work as well.
See http://rabi.phys.virginia.edu/HTW/flashlights.html:
How can you run a clock off of a potato?
The classic technique is to insert two dissimilar metal strips into
the potato in order to build a simple battery. You can then run an
electronic clock with the power provided by that battery. But the
energy in that battery is coming from chemical reactions of the metals
and not really from the potato.
Also http://www.newscientist.com/lastword/answers/349gadgets.jsp?tp=gadgets1:
The energy powering the potato clock does not come from the potato,
but simply from the electrochemical properties of two different metals
being placed into a salt solution. As the questioner correctly notes,
cola also works, as does any simple salt solution--try it with table
salt. The potato acts as a compact, slow-to-dry, salt bridge.
The metal electrodes are slowly dissolved (or at least one of them is)
as part of the electrochemical reaction. The power comes from the fact
that the different metals have different electrode potentials. It is
not coming from the electrolyte.
Hal
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