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Conceptual Questions No.1- Battery
The teacher was reviewing VOLTA experiments and how battery invention. One of the students asked him:
In battery, after finishing of its construction and positive & negative electrode creation, why we will need an external electrical lead (for example copper wires) for transmission of energy between two poles?

Why no short circuit occurs between positive and negative electrodes through battery electrolyte and why electrical potential difference is stable in battery?
Author : Hamid - From: Iran
Mon, August 31st, 2009 - 10:38
In the battery, the positive and negative polarities are relative concepts. In deed, in battery system one of the two poles is for example negative and the other is more negative in comparison with the electrolyte material.
In fact, in a separated battery bank after electrochemical stability, the charge transmissions between electrolyte media and both of two electrodes will be stopped and opposite transmission current will be impossible.
A similar mechanical phenomenon is heat transmission between two metal rods with different thermal conductivity coefficiency that are connected to a very hot metal plate. The thermal difference at the end of rods can cause the heat transfer through a metal wire between them, but the heat transmission between two rod is impossible through the hot metal plate because the plate is warmer than both of them.

Author : Hamid - From: Iran
Mon, August 31st, 2009 - 10:41
This is an over simplification but:

In an electrochemical cell as described there are in fact electrons leaving the negative plate and going into the solution and electrons leaving the solution and entering the posative plate.  The catch is that there are just as many going in the other direction.

The cell is not static but is in equilibrium where the electrical potential is balancing the chemical potential. 
Author : Stephen Byrne - From: Australia
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