BharatNotes What is Galvanic Cell?
A galvanic cell (or voltaic cell) is an electrochemical device that converts the chemical energy of a spontaneous oxidation–reduction (redox) reaction directly into electrical energy. It comprises two half-cells: at the anode (negative terminal) oxidation releases electrons, and at the cathode (positive terminal) reduction consumes them. Electrons flow from anode to cathode through the external circuit, while a salt bridge (typically containing an inert electrolyte such as potassium nitrate or potassium chloride) completes the internal circuit and maintains electrical neutrality in both solutions.
The classic example is the Daniell cell, made public by British chemist John Frederic Daniell in 1836. A zinc electrode in zinc sulphate solution (anode: Zn → Zn²⁺ + 2e⁻) is paired with a copper electrode in copper sulphate solution (cathode: Cu²⁺ + 2e⁻ → Cu), generating an EMF of about 1.1 volts. It was the first reliable steady source of current and powered early telegraph systems.
Historical Background
The name honours Luigi Galvani, who from around 1780 observed that dissected frog legs twitched on contact with two different metals (findings published in 1791). Alessandro Volta correctly attributed the effect to the metals rather than "animal electricity" and in 1800 built the voltaic pile — alternating zinc and copper discs separated by brine-soaked cardboard — the first battery.
Key Features
| Feature | Galvanic Cell | Electrolytic Cell |
|---|---|---|
| Energy conversion | Chemical → electrical | Electrical → chemical |
| Reaction type | Spontaneous redox | Non-spontaneous (driven by external source) |
| Anode polarity | Negative | Positive |
| Example | Daniell cell, dry cell | Electroplating, electrolysis of water |
In both cell types, oxidation always occurs at the anode and reduction at the cathode — a frequent examination trap.
Significance and Applications
Every commercial battery is a galvanic system: primary cells (dry cells, button cells) are used once, while secondary cells (lead–acid, nickel–metal hydride, lithium-ion) are rechargeable — functioning as galvanic cells while discharging and electrolytic cells while charging. Fuel cells, such as the hydrogen–oxygen cell relevant to India's National Green Hydrogen Mission, are galvanic cells fed continuously with reactants. The 2019 Nobel Prize in Chemistry went to John B. Goodenough, M. Stanley Whittingham and Akira Yoshino for developing lithium-ion batteries — the technology behind mobile phones, electric vehicles and grid-scale renewable-energy storage. The galvanic principle also explains galvanic corrosion, where the more reactive of two joined metals corrodes preferentially — exploited deliberately in sacrificial zinc coatings (galvanisation) to protect iron.
UPSC Angle
For Prelims, master the anode–cathode convention, the direction of electron versus current flow, the role of the salt bridge, and the galvanic–electrolytic distinction. For GS3 Mains, the concept anchors answers on battery energy storage systems, EV ecosystems, the FAME scheme context, green hydrogen and fuel cells, and critical minerals (lithium, cobalt) — domains where UPSC increasingly frames applied science-and-technology questions.
