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What is citric acid

My experiment is to see which fruit produces the most voltage, using a copper and zinc nail, a multimeter, alligator clips, 3 lemons, 3 oranges, and 3 oranges. Part of the experiment includes research. I have heard that there is something called citric acid ⇦this on eBay or Amazon [affil links] that helps produce the voltage. Could you explain what it is and what it has to do with the voltage?

Thank you.

Eric T.
student (grade 6) - Fullerton, California
2004

citric acid is the name of an acid found in citrus fruits, such as lemons, limes and oranges. The voltage you will get from the two nails will be due to something called the "electrode potential" of the individual metals. The electrode potential is a measurement of the reactivity of the metal in the acid.

Since part of your assignment is to do some research, I suggest you do some! Research is about experimenting, observing what happens and trying to understand it! This is what makes a good scientist and furthermore, it makes science bearable! If I didn't have the chance of doing experiments, I couldn't have thought of taking such a boring subject as science, but actually DOING things made it so much more exciting. For instance, many millions of people have wondered, over the centuries, what it would be like on the moon - Neil Armstrong was the first person to go there and find out; what a man!

Back to the assignment - try putting your nails into other things, such as potatoes, strawberries, tapwater, carbonated drinks, the earth, etc. See what happens and try to explain it.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004