Galvanic cell
A galvanic (voltaic) cell turns a spontaneous redox reaction into electric current. Oxidation happens at the anode and reduction at the cathode. Electrons flow through the wire from anode to cathode. A salt bridge keeps the charge balanced.
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Analogy
A water wheel: the electrons 'fall' from a high-energy to a low-energy place and do work on the way.
Example
Anode: Zn → Zn²⁺ + 2e⁻Cathode: Cu²⁺ + 2e⁻ → CuElectrons flow Zn → CuZn electrode dissolves, Cu grows
In practice
Batteries, from a torch cell to a phone battery, are galvanic cells packaged in a sealed case.
Practice
Flashcards
- Which electrode is the anode?The one where oxidation happens.
Interview questions
- Describe a Zn/Cu galvanic cell, label the electrodes, and calculate E°cell.
- Zn anode: oxidation
- Cu cathode: reduction
- Electrons flow from Zn to Cu
- E°cell = 0.34 − (−0.76) = 1.10 V
Questions people ask
What does the salt bridge do?
The salt bridge lets ions move between the two half-cells. Without it, positive charge would build up in the anode compartment and negative charge in the cathode compartment, which would stop the flow of electrons almost at once. It completes the circuit.
How can I remember anode and cathode?
The mnemonic is AN OX and RED CAT: oxidation happens at the anode, and reduction happens at the cathode. This is true for both galvanic and electrolytic cells. What differs is the sign of the electrodes: the anode is negative in a galvanic cell.