Electricity from fruit (cont'd)

A. Hi, Alex.

It might be best to get a commercially available "potato clock" and see if there is a manufacturer name and model or part number on the display. With today's highly integrated electronics, I'd bet that any necessary drivers and decoders are built right into the display; I doubt that there are any other electronic parts required. It looks like they run off of two potatoes in series (probably about 2 volts for a device rated for 3). My own experience is that electronics are dirt cheap if you buy ten million but unfortunately very hard to find inexpensively if you only need a few :-(  Good luck.

Regards,

A. Hi, Jun. There are 10 acids in tomatoes: acetic, lactic, fumaric, malic, pyrrolidone carboxylic, citric, phosphoric, umbiolic, hydrochloric, sulfuric, and galacturonic. Oops, I listed eleven instead of ten; I guess I just sat here and made one of them up :-)
This illustrates the fact that a public internet forum may steer you in the right direction, and it may give you some good answers, but they probably will be mixed in with bad answers. And the question becomes how to judge whether the information is trustable or not? What do you suppose this project is supposed to be teaching you about how to do research? If you look up those 11 acids there will be one that nobody ever heard of because there is no such thing :-)

Good luck, and Regards,

A. Yes, Melanie, you can. If one fruit battery gives you 1.0 volts, then 5 in series would give you 5 volts. I'm not sure what voltage your phone needs, but that's how you figure it, and 5 volts may be enough -- but you probably don't have enough current without a bunch of sets of 5 wired in parallel.

Regards,

A. Hi, Akansh. You can use any two dissimilar metals you wish. Silver and steel for example. The voltage that the battery generates will depend on which two metals you pick and how far away from each other they are on a chart called "the galvanic series". But I don't understand why you don't want to use zinc when it is cheap, readily available, and produces good voltage. Good luck.

Regards,

A. Hi, Bill.

A potato doesn't really "make electricity" in any different sense than a glass of saltwater makes electricity. The salts in the potato are simply conductive like saltwater. As long as the potato doesn't dry up, so there is a wet conductive path between electrodes of two different metals, electricity should continue to flow. But as it flows, one electrode becomes slowly coated with whatever metal the other electrode is made of. And once it's completely coated, there's no difference in the surfaces anymore, and the battery dies.

Regards,

A. Hi, Tanner.

Let me ask you a question first...

Who discovered that 12345 plus 56789 plus 34556 equals 103,690? It's possible that nobody ever added those three numbers to together, and that you & I are the first to ever discover it! . . . still, it doesn't impress us much because it's not so much a real "discovery" as it is just combining some very simple known facts to arrive at a reasonable conclusion.

Similarly, if we already know that electricity will flow through conductive liquids, and we already know that fruits contain conductive liquids, it wasn't really much of a discovery. But at some point in your science education you might decide to research who first discovered that electricity will flow through conductive liquids and postulated how. Good luck on your project!

Regards,

A. Hi Ruby. No, it doesn't work if the same metal is used for both electrodes.

Regards,

A. Hi Yatharath. We weren't in the classroom with you and don't know exactly what you are questioning. So you need to take the time to very clearly explain what you understand and what you do not yet understand -- because we will only further confuse you by attempting to answer vague questions :-)
1. Do you very very clearly understand exactly what you mean by "conduct electricity"? Because the answer is: certainly stainless steel electrodes will "conduct electricity". But if you don't very clearly understand your question you will probably leap to all the wrong conclusions :-(
2. Does juice play any role? Of course it does, but juice would never be used in commercial production of electricity.
3. Electrical conductivity is a fairly specific term meaning the inverse of electrical resistivity. But that probably doesn't help you.
4. Juice "conductivity" is the same thing.

Please please please take the time to clearly phrase your questions in terms of words you already clearly understand, and then I am sure I can help you. But if you simply mouth terms and phrases that you don't really understand I will just be leading you deeper into confusion :-(

Regards,

A. Hi cousin Kioria. I don't think it's helpful to a person's education to answer a question if the person asking the question does not understand what they are asking. If you can phrase your question in such a way as to demonstrate that you very clearly understand your own question, I will be happy to try to answer it. But if you don't understand the question, you must ask your teacher to carefully explain the question rather than attempting to provide him/her an answer to a question you don't understand. Good luck.

Regards,

A. Hi Nehal. Are you sure that you know what you mean by resistance? And what a potentiometer is? And that you truly visualize the situation described by your question? If you don't, you must explain to the teacher that you don't understand the question.

1. Potentiometer

2. Potentiometer (measuring instrument)

What you want to do is not impossible, but I'm thinking it would be a bit silly, with the fruit hooked up as R_L in the graphic of the first Wikipedia article.

Actually, I think you've misworded the question, and I suspect that after you talk to the teacher you will want to look at "unknown voltage" in the graphic of the second Wikipedia article instead. Best of luck.

Regards,

A. Hi Tiana. Fruits and vegetables do not have "electric charge". But their juices will conduct electricity in the same way as water, especially salt water, does.

Regards,

A. Hi Vidhi. Sorry, no, that's not explicable in my experience. But if you provide facts & figures, someone may be able to deduce a pattern from them.

Regards,

A. Might it be that the different solutions tested had varying conductivities, and the resistance between the electrodes became a limiting factor? Although, with both electrodes of the same metal, there should be no current flow at all anyway.

Hi Robin. If you have the patience to slowly think this through, I think you can largely understand it even though parts may be beyond your experience and mine...

The most basic thing that happens is that if you put a metal rod into a mild acid like a fruit juice, a very small amount of the metal will dissolve into the acid, similar to the way that a certain amount of salt or sugar will dissolve into water. That is, a few of the metal atoms on the surface separate into positively charged ions of the metal that go into solution, and negatively charged electrons that accumulate on the rod. A balance is achieved whereby these positively charged dissolved ions are constantly drawn back to the negatively charged electrons on the metal, but as they reach it, another metal atom dissolves to keep the balance.

If you put rods of two different metals, say zinc and copper, into the acid, a small amount of zinc ions will go into solution and a small amount of copper ions will go into solution in the same way. But if you now connect a wire between the two rods, so that electrons can flow from one rod to another, things change because the zinc ions are stronger at wanting to go into solution, and the copper is stronger at grabbing the electrons and coming out of solution. So, a zinc ion will go into solution and a copper ion will deposit on the zinc rod by grabbing an electron and becoming a copper atom again. As this occurs the copper rod will dissolve more atoms into positively charged ions and negatively charged electrons, depositing onto the zinc rod, and force a zinc atom to ionize into solution. But since electrons are now free to travel from one rod to the other via the wire, they will flow from the copper rod to the zinc rod, and as they do, since negative charges are no longer building on the copper rod, it can continue to dissolve, and since electrons are now building on the zinc rod, they can neutralize copper ions into copper metal deposits. Eventually the zinc rod becomes completely covered with copper and everything stops.

Regards,

Hi Cameron. Any of the three will be fine. But your wording "producer of electricity" is vague and misleading. These fruits & vegetables do not produce electricity; they are simply conductive (which means that atoms of metal can dissolve into them). Ketchup or vinegar ⇦in bulk on eBay or Amazon [affil links] will do the same.

Regards,

A. Hi Adrian. I think your multimeter is set on the wrong scale. It should be set for DC volts, probably 0-10 VDC or something like that. Then your AA battery will read 1.5 Volts, and your copper coin to zinc nail will read about 1.0 Volts.

3.62 MHz means 3,620 cycles per second on and off, and has nothing to do with AA batteries or lemon / potato batteries. Good luck.

Regards,