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Voltaic Cell
- A Voltaic cell is also called a Galvanic cell.
- It has two metal plates of different materials.
- These plates, called electrodes, dip in a liquid.
- The liquid, called an electrolyte, is a weak acid or salt solution.
- A chemical reaction makes electric current.
Example 1 — Working Cell
- The circuit of the cell is connected.
- Current flows from the positive to the negative terminal.
- So the cell lights a small lamp.
Example 2 — Dead Cell
- The chemicals in the cell get used up over time.
- The cell stops making current.
- So the cell is called dead.
Important Points
- The metal plates are the electrodes.
- A dead cell cannot supply any more electricity.
Definition — Voltaic Cell
A Voltaic cell has two different metal electrodes in a liquid electrolyte, where a chemical reaction makes electric current.
Definition — Electrolyte
An electrolyte is the liquid in a cell, usually a weak acid or salt solution, that helps make current.
🏭 Ever Heard Of — Volta and Galvani
The Voltaic and Galvanic cells are named after Italian scientists Alessandro Volta and Luigi Galvani.
The story
In the late 1700s, Galvani saw a dead frog's leg kick when touched with copper and iron. He thought the electricity came from the frog. Volta thought it came from the metals. He used saltwater-soaked paper instead of the leg and still got current. This showed metals and liquid together make current, and led to the first battery.
Materials needed
Five or six juicy lemons.
Copper wires or strips and iron nails.
One LED and some connecting wires.
Copper wires or strips and iron nails.
One LED and some connecting wires.
Procedure
Insert a copper wire and an iron nail in each lemon, kept apart.
Join the copper of one lemon to the nail of the next.
Connect the LED across the first and last lemon.
If the LED does not glow, reverse its connections.
Join the copper of one lemon to the nail of the next.
Connect the LED across the first and last lemon.
If the LED does not glow, reverse its connections.
Observation
The LED glows, which shows the cell is working. It glows only when the LED terminals match the battery terminals.
Explanation
Here the copper and iron are the electrodes and the lemon juice is the electrolyte. So the lemons make a Voltaic cell.
◆ Summary
- Copper and iron electrodes.
- Lemon juice is electrolyte.
- LED glows, cell works.
- Match the LED terminals.
⭐ A Step Further — Metal Pairs for Cells
Some common metal pairs for Voltaic cells are zinc/copper, aluminium/copper, and magnesium/copper.
Some metals, like copper, act as positive electrodes. Others, like zinc, act as negative electrodes. This is due to their chemical properties.
