# Galvanic cell A galvanic cell is a [[Redox]] reaction with its two halves physically separated, so the electrons have to travel through a wire to get from one to the other. That detour is the point: the same chemistry that would release its [[Energy]] as heat instead delivers it as [[Voltage]] and current. Every battery is one. ## Microsim — p5.js Sidecar: `Galvanic_cell.p5.js` · route leaf: `microsim/p5js/Galvanic_cell__20260910T0400Z`. Built to the Betterfire Standard v0 (single `ARTICLE` constant, HUD title and Wikitube URL, control hints, parameter readout and equation). | Control | Does | |---------|------| | `E° slider` | difference between half-cell potentials | | `load slider` | external resistance | | `[b]` | open or block the salt bridge | *What to watch:* Electrons stream through the wire while ions cross the bridge the other way. Pinch the salt bridge shut and everything stops within a second — charge balance is not optional. ## Splitting the reaction in two Oxidation happens at the anode, reduction at the cathode, and a salt bridge or membrane carries ions to keep each side electrically neutral — without it, charge builds up and everything stops within moments. The cell potential is the difference between the two half-cell potentials, and the maximum electrical work available is ΔG = −nFE, which ties the whole device back to [[Gibbs_free_energy]]. Reverse the current from outside and it becomes [[Electrolysis]]. ## Where the losses live The measured voltage under load is always below the thermodynamic ideal. Overpotential at the electrodes, the resistance of the electrolyte, and reactants failing to reach the surface fast enough all take their cut — which is why [[Electrochemistry]] treats [[Diffusion]] and flow as part of the problem rather than a detail. The same accounting governs a [[Fuel_cell]], which is a galvanic cell fed continuously instead of one carrying its reactants inside, and [[Corrosion]], which is a galvanic cell nobody wanted. **Reads with:** *Thermodynamics and Chemistry, 2nd ed. (Howard DeVoe, 2020)* — [OTL record](https://open.umn.edu/opentextbooks/textbooks/thermodynamics-and-chemistry) · [download](https://www2.chem.umd.edu/thermobook/downloads.htm) · CC BY 4.0. Section 6 of the [[PORTAL_Thury_Hydrodynamics_Apex_Spine|Apex Spine]] book shelf. **On the spine:** [[Electrochemistry]] · [[Redox]] · [[Gibbs_free_energy]] · [[Electrolysis]] · [[WT!Thury_Hydrodynamics_Compendium]]. ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Galvanic_cell) : [Wikitube](https://en.wikitube.io/wiki/Galvanic_cell) ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Hydrogen]], [[PORTAL_Oxygen]]. --- *Book-section wave · 2026-09-10 · article + p5 microsim shipped together.*