I've done this experiment myself and seen it front of my eyes. Set up a basic circuit with a battery, an LED, and connect the circuit with a salt-water solution and copper wire. The LED lights up.

If a potential difference is applied across two ends of the wire with the battery, positive charges move towards the end with lower potential and negative charges towards the higher potential.

Why does this conduction keep continuing? Shouldn't there eventually be a pile up of Na+ and Cl- on opposite ends to cut off the circuit? This is with a typical 9V battery. Is there a teensy bit of electrolysis going on in the wire that continuously supplies electrons to the circuit?

EDIT: In doing my own reading the next day, I seem to have forgotten the very important fact that water itself is electrolyzing at the surface of the electrodes. The salt water only helps to prevent the resulting electrolysis from quickly shielding the electrodes. The reason I was confused was because I was very skeptical of NaCl being electrolyzed and turns out this is exactly not the case


Without electrolysis, there would be just an extremely short spike of a temporary initial current, until capacitors formed by electrodes charge.

There is no significant accumulation of ions, as even a tiniest such charge separation would cause strong electrostatic forces acting against it.

  • $\begingroup$ I don't know if I agree with the last comment there. I'm applying a potential difference across two wires so there is an electric field that pushes charges. In an ideal plasma, these charges move according to this field with the net effect being that they screen the electric field eventually, but there has to be movement initially applied with the potential difference right? $\endgroup$ – cheekylittleduck Apr 5 at 14:20
  • $\begingroup$ For the first comment, is this just confirming that in my kitchen I am making sodium metal and chlorine gas with a 9V battery? $\endgroup$ – cheekylittleduck Apr 5 at 14:21
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    $\begingroup$ @cheekylittleduck When you electrolyse salt water, you are making hydrogen gas, and chlorine gas (mainly) in the electrodes. Look up the table of electrode potential, and you will see that it's much easier to reduce H+, or H2O into H2 gas than to reduce Na+ to Na. $\endgroup$ – Shoubhik R Maiti Apr 5 at 17:09
  • $\begingroup$ @Cheekylittleduck I have said significant. Apply the Coulomb law. Ions separate until creating the ion displacement potential difference cancelling the external one. Unless electrode reactions happen, which cancels this displacement.// No sodium, unless using melted NaCl, or mercury cathode with concentrated NaCl. $\endgroup$ – Poutnik Apr 5 at 21:39

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