Lemon battery
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The lemon battery is an experiment proposed as a project in many science textbooks around the world. [1]. It consists of inserting two different metallic objects, for example a galvanized nail and a copper coin, into a lemon. These two objects work as electrodes, causing an electrochemical reaction which generates a small amount of electricity.
The aim of this experiment is to show students how batteries work. After the battery is assembled, a multimeter can be used to check the generated voltage. In order for a more visible effect to be produced, the battery can be used to power a LED. Since the produced voltage is typically insufficient to power a standard LED, two or more batteries are connected in series.
In a lemon battery, both oxidation and reduction occur. At the anode, zinc is oxidised:
- Zn → Zn2+ + 2 e-
At the cathode, hydrogen is reduced:
- 2H++ 2e- → H2
Potatoes [2], apples, or any other fruit or vegetable containing acid or other electrolyte can be used, but lemons are preferred because of their higher acidity [3] [4]. Other metal combinations (such as magnesium-copper) are more efficient, but zinc and copper are usually used because they are reasonably safe and easy to obtain.
Using a magnesium strip instead of zinc approximately doubles the current produced by the lemon cell (approx. 240 µA with zinc to about 400 µA with magnesium) and increases the voltage (.97 V with zinc to 1.6 V with magnesium). These numbers, of course, depend upon your lemons.
[edit] Warning
This experiment may leave the lemon's juice poisonous because of dissolved copper salts.
[edit] External links
- Lemon Battery, Hila Research Center
- The Lemon Battery Challenge, National Engineers Week
- D.J. Swartling, C. Morgan (1998). Lemon Cells Revisited—The Lemon-Powered Calculator. Journal of Chemical Education, 75 (2), page 181.
