What is a Galvanic Cell?
A galvanic cell (or voltaic cell) is an electrochemical device that converts a spontaneous redox reaction into electrical energy. The anode oxidises, the cathode reduces, and electrons flow through an external circuit.
A galvanic cell is a spontaneous electrochemical cell where a redox reaction produces electrical current. Anode (oxidation), cathode (reduction), salt bridge (ion flow), and external wire (electron flow).
- 1↓AnodeOxidation site; loses electrons (negative electrode)
- 2↓External WireElectrons flow from anode to cathode; powers devices
- 3↓CathodeReduction site; gains electrons (positive electrode)
- 4↓ElectrolyteContains ions; conducts charge inside the cell
- 5Salt BridgeAllows ions to flow, maintaining electrical neutrality
Step-by-step worked examples
In a Daniell cell (Cu²⁺/Zn²⁺), which electrode is the anode and which is the cathode?
Oxidation (loses electrons) is Zn: Zn → Zn²⁺ + 2e⁻ (Anode) Reduction (gains electrons) is Cu: Cu²⁺ + 2e⁻ → Cu (Cathode) Anode: Zn (negative); Cathode: Cu (positive)
In a galvanic cell, where do electrons flow?
From anode to cathode through the external wire/circuit. Electrons cannot flow through the electrolyte (non-conductor inside). Cations move through the salt bridge to balance charge inside the cell.
Why is a salt bridge necessary in a galvanic cell?
Without it, positive charge builds up at anode (Zn²⁺ produced) and negative at cathode (Cu²⁺ consumed). Salt bridge allows anions to migrate toward anode and cations toward cathode. This maintains electrical neutrality and allows the reaction to continue.
Flashcards
Quick quiz
Q1.In a galvanic cell, where is oxidation?
Q2.What flows through the external circuit in a galvanic cell?
Q3.Without a salt bridge, what happens?
Q4.In a Zn/Cu Daniell cell, Zn is the…
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Common mistakes
Thinking electrons flow through the electrolyte. — Correct: Electrons flow through the external wire only. Ions flow inside through the salt bridge.
Confusing anode with positive electrode. — Correct: In galvanic cells, anode is negative (oxidation site).
Thinking the salt bridge passes electrons. — Correct: The salt bridge conducts ions only, not electrons.
Believing galvanic cells require an external power source. — Correct: Galvanic cells are spontaneous; they generate electricity without external input.
FAQ
What is the difference between a galvanic and electrolytic cell?
Galvanic cells are spontaneous (generate electricity); electrolytic cells require external power to drive a non-spontaneous reaction.
How long does a galvanic cell produce current?
Until one reactant is consumed. The reaction continues until equilibrium or depletion.
Can you measure galvanic cell voltage?
Yes, the electromotive force (emf) is the cell potential, measured in volts. In Daniell cells, it's typically ~1.1 V.
What is the most famous galvanic cell?
The Daniell cell (Zn/Cu/ZnSO₄/CuSO₄) was one of the first practical cells, used in telegraphs.