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How I am interested in understanding what is the actual mechanism behind increasing potential in simple galvanic cell connected in series. Almost all explanations I found on internet are more like recursive "explanation from definition". First we define that each cell adds potential difference and then it becomes the actual explanation. I am feeling that this lacks an actual chemical insight of why electrons experience more EMF in such circle. So I am trying my luck here. This duplicate left with no answer.

To make question more concrete consider the following:- suppose you can examine only one cell in galvanic (classical Zn/Cu) battery you do not know where its anode and cathode are connected. However you do know that the circuit is closed. Will it be possible by observation of chemical/electrical/atomical process in it to know that it connected in series or not? In other words will it be possible to determine that this is the only source of EMF? If yes what chemically/electrically changes will it experience vs the condition where it works alone.

And yes I do not have any real background in chemistry or electronics so use simple English :)

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  • $\begingroup$ No. If you could examine what is going on that cell from inside you won't be able to tell if it is one or one of a series. $\endgroup$ – Alchimista Oct 13 '17 at 13:51
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Electrons in the wires do not "know" whether there is a particular chemical cell, or more than one cell... that information is lost. However, one can infer if there are multiple cells in series from the current during discharge, if the cells have different capacities. For example, voltage from a small carbon-zinc cell in series with one much larger would be ~3 V open circuit, drop fairly quickly to ~1.5 V with increasing current, and then drop more slowly as current increases further.

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  • $\begingroup$ We don't have to go to discharge actually. The potential accumulated on cathode in disconnected state will be three times more when connected say three cells in batterym than on single one. Is it right? $\endgroup$ – Boris Oct 15 '17 at 20:15
  • $\begingroup$ Not in the case of different cell chemistries: If ~3.2 V is measured, it might be a single Li cell, two fresh Zn-C cells in series or three Ni-Fe cells in series. $\endgroup$ – DrMoishe Pippik Oct 16 '17 at 22:07
  • $\begingroup$ Thanks a lot for response. Can you comment on my answer? It is based on your input and comments are limited in size to put it here. $\endgroup$ – Boris Oct 17 '17 at 1:58
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Ok let's reduce the scope to only one classical Zn/Cu battery. (The real reason behind it is that I am not familiar with any other :)) Also we will reduce the characteristics of the circuit to most simple one. Battery (new cells with well known characteristics) and resistor as a load. The answer it my question would be.

Can we by observing only the first cell know if it is acting alone or connected in series....

  1. Yes it is possible by observing the number of electrons in disconnected state on the cathode . It should be times higher than when cell is acting alone.
  2. The reason behind it is that when cell is connected in series they can "borrow" more charge from cells behind before the reaction stops (when circuit is disconnected).
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  • $\begingroup$ Using ohm's law, for an infinitely large cell, the current will scale with voltage. In real life, for small cells and small resistances, the internal cell resistance cause two cells in series to produce less than two times as much current as for a single cell. You may be confusing current (number of electrons or coulombs moved/second) with potential (electromotive force, voltage). $\endgroup$ – DrMoishe Pippik Oct 17 '17 at 17:59

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