Order can be stored as a concentration difference and spent as current.

The Nernst equation relates an electrochemical cell’s voltage to temperature, ion concentrations, and the number of electrons transferred in a reaction. It extends the standard electrode potential to real conditions, where chemical species are rarely present at standard concentrations. As concentrations shift, the equation shows how the electrical driving force shifts with them. This makes it a compact bridge between chemistry and voltage. In biological systems, the same relationship helps explain the equilibrium potential of ions across cell membranes. It is used primarily in electrochemistry, analytical chemistry, and cell physiology.