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One of the things that may not
be "obvious" from the experiment we did is that redox
reactions which can be used to generate voltage are not as
restricted as the procedure we used might imply. Almost any
metals with almost any electrolytes (as opposed to a metal with
its own ion in solution) will generate some kind of electric
potential. In the case of elements which are not metals or even
those which are in ionic form, electrical contact is often
possible through inert conductors like graphite or platinum.
However, the most stable
results are generally obtained with electrodes related to the
ions in solution.  
When a voltmeter is used to
detect electric potential, certain conventions are used to
determine the eventual direction of electron flow. We
must say "eventual" because the resistance to electron
flow in a voltmeter is generally very high and no actual reaction
takes place when electrodes are connected to the voltmeter. If the
electrodes are joined directly with a wire, electrons flow in the
direction indicated by the voltmeter.
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