Lemon Battery
A lemon battery is a simple battery often made for the purpose of education. Typically, a piece of zinc metal (such as a galvanized nail) and a piece of copper (such as a penny) are inserted into a lemon and connected by wires. Power generated by reaction of the metals is used to power a small device such as a light emitting diode (LED).
檸檬電池類似於Alessandro Volta在1800年發明的第一個電池，它使用鹽水（鹽水）代替檸檬汁。[1]檸檬電池說明了電池中發生的化學反應（氧化還原）的類型。[2] [3] [4]鋅和銅被稱為電極，檸檬內的果汁被稱為電解質。檸檬細胞有許多變種，使用不同的水果（或液體）作為電解質和鋅和銅以外的金屬作為電極。
The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta, who used brine (salt water) instead of lemon juice.[1] The lemon battery illustrates the type of chemical reaction (oxidation-reduction) that occurs in batteries.[2][3][4] The zinc and copper are called the electrodes, and the juice inside the lemon is called the electrolyte. There are many variations of the lemon cell that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes.
Many fruits and liquids can be used for the acidic electrolyte. Fruit is convenient, because it provides both the electrolyte and a simple way to support the electrodes. The acid involved in citrus fruits (lemons, oranges, grapefruits, etc.) is citric acid. The acidity, which is indicated by the measured pH, varies substantially.
Potatoes have phosphoric acid and work well; they are the basis for commercial "potato clock" kits.[8][9] Potato batteries with LED lighting have been proposed for use in poor countries or by off-grid populations. International research begun in 2010 showed that boiling potatoes for eight minutes improves their electrical output, as does placing slices of potatoes between multiple copper and zinc plates. Boiled and chopped plantain pith (stem) is also suitable, according to Sri Lankan researchers.
Instead of fruit, liquids in various containers can be used. Household vinegar (acetic acid) works well.Sauerkraut (lactic acid) was featured in one episode of the US television program Head Rush (an offshoot of the MythBustersprogram). The sauerkraut had been canned, and became the electrolyte while the can itself was one of the electrodes.
Zinc and copper electrodes are reasonably safe and easy to obtain. Other metals such as lead, iron, magnesium, etc., can be studied as well; they yield different voltages than the zinc/copper pair. In particular, magnesium/copper cells can generate voltages as large as 1.6 V in lemon cells. This voltage is larger than obtainable using zinc/copper cells. It is comparable to that of standard household batteries (1.5 V), which is useful in powering devices with a single cell instead of using cells in series.
The energy comes from the chemical change in the zinc when it dissolves into the acid. The energy does not come from the lemon or potato. The zinc is oxidized inside the lemon, exchanging some of its electrons with the acid in order to reach a lower energy state, and the energy released provides the power.
In current practice, zinc is produced by electrowinning of zinc sulfate or pyrometallurgical reduction of zinc with carbon, which requires an energy input. The energy produced in the lemon battery comes from reversing this reaction, recovering some of the energy input during the zinc production.
心得:這次的報告讓我學到原來檸檬也可以當作電池來發電，我覺得還蠻有趣的。
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