Electrochemical Cells - Explanation
Electrode potential: the voltage measured when a half-cell is connected to a standard hydrogen electrode
E.C. Cells can be made from two different metals dipped in salt solutions of their own ions and connected by a wire (the external circuit).(diagram 1)
There are always 2 reactions within an electrochemical cell - an oxidation and a reduction - it's a redox process.
Electrons flow through the wire from the most reactive element to the least reactive.
A voltmeter in the external circuit shows the voltage between the two half-cells. This is the cell potential or e.m.f., E.cell
You can also have half-cells involving solutions of two aqueous ions of the same element, using the standard hydrogen electrode (diagram 2).