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Which vegetable is the best conductor of electricity

I am trying to guide my son on his science project. He is in the sixth grade and made the hypothesis, if water is a good conductor of electricity, then the vegetable with the highest concentration of water would be the best conductor. We have researched the water concentrations of vegetables together to pick some that have high, medium, and low concentrations. We have also researched electricity and found that different metals will form an electrical reaction which I believe may skew his results by either increasing the electrical current that passes through the vegetable or elements in the fruit giving resistance to the flow. Should we just be powering from a battery with one wire to the vegetable and then using a voltmeter to read the level of the results to do the experiment? Or should we be using both copper and zinc leads to the vegetable and then reading the results?

Sylvia K.
student - Bay Shore, New York
November 23, 2009

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Hi, Sylvia. You must put only one type of metal in the vegetable or you will be creating a battery and skewing the results. If it's a cheap meter, just stick both leads into the vegetable at a consistent distance apart (say 1 inch) and read the resistance on the meter. The test is not perfect since the vegetables will have different cross sections, so you could improve it by cutting them into 1-inch cubes or some other consistent shape that suits all the vegetables. Conductance is the reciprocal of resistance.

I suspect that your son's hypothesis will be proven wrong, but there is nothing wrong with that. A hypothesis is only an educated guess, and science progresses as the educated guesses are proven wrong.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 24, 2009

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Sylvia,
Keep in mind that vegetables that are slightly or highly acidic should be considered in the experiment. We use acids for the same reason in electroplating.

Mark Baker
Fellow Plater - Syracuse, New York
November 25, 2009

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See also (i.e. google search):
potato battery
electric pickle

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

December 7, 2009