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Q & A: Potato Battery

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Most recent answer: 10/22/2007
how do i make a potato battery
- Anonymous (age 10)
I found this on the web. Hope it helps


What you need is a spud. Idaho potatos work best. (Well, I don't know that for a fact. That was just a plug on my part for Idaho. You can substitute any other potato -- or any other vegetable for that matter. The potato is the traditional, hands-down-favorite vegetable battery electrolyte). You also
need two lengths of copper and zinc metal. These you cannot substitute. It has to be copper and it has to be zinc. It is the chemical reaction between these metals that powers the battery.

Finger-length is long enough for these metals. Stick the copper in on one side of the potato, and the zinc on the other side. The zinc and copper fingers should not touch each other in the potato. The zinc and the copper are the anode and cathode terminals of your potato battery. Using ordinary hook-up electrical wire, you can use the potato battery to power a small bulb (and I do mean small! This battery will only put out about half a volt!)

The power of the battery comes from the electro-chemical reaction of zinc with copper. The potato does not participate directly in the reaction. It is there rather as an electrolyte to facilitate the transport of the zinc and copper ions in the solution while keeping the copper and zinc fingers apart. If the zinc and copper are in contact with each other, their reaction will still occur, but only heat will be generated. By keeping them apart, we force the electron transfer that occurs in the reaction to take place over the wires of our circuit.

Best regards,

Max Godfrey

(published on 10/22/2007)

Follow-Up #1: fruit batteries: pears

Hi all.

I was originally drawn here for some of the "potato battery" questions, and ended up doing my science fair on it. I took pears, lemons, limes, carrots, and potatoes, and tested them with this method to see which could produce the most voltage. I hypothesized that the more acidic produce would make more voltage. This was what hapenned until I got to the pears, which, although less acidic than the lemon and limes, still produces more voltage. Do you have any idea why this would be? Science fair is long over, but I am still wondering what the cause would be. Maybe it has something to do with what I will learn next year in Chemistry, as I am in Bio right now.

- Johnny D. (age 15)
Harrisburg, PA, USA
We don't actually know the answer to this. It seemed best to let you know right away and also to hope that some reader might be able to help out.

Mike W.

Lee H

(published on 10/22/2007)

Follow-up on this answer.