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"Electricity from fruit (cont'd)"




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An ongoing discussion beginning back in 2003 ...

June 6, 2009

Q. On fruits and vegetable my daughter has to make a graph of her findings and its her first time using a analog multimeter and we are confused

Amber O [last name deleted for privacy by Editor]
student - Brooklyn, New York
^


June 7, 2009

Q. I'm doing a science project for 6th grade and I wanna know if you know why my potato powered a clock longer than my lemon but the opposite for my friend?

Kimberly M [last name deleted for privacy by Editor]
Student - Beverly Hills, California
^


"Pop Bottle Science"
from Abe Books

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July 3, 2009

A. Hi, Amber. A graph is a mathematical language we use to illustrate and explain a relationship between two or more things. What exactly is it that you would like the graph to illustrate and explain? Your question is a bit like saying that your daughter has to write up her project in Spanish or French, so she is confused about what to write :-)  Start by expressing her findings in English, and I'll explain how to graph those findings. Good luck.

Hi, Kimberly. We've tried to explain several times why such a variation can exist, but it's probably just random depending on the particular nail, penny, the spacing between them, and particular sample of fruit and vegetable. But frankly you may be focusing your attention on a triviality. Do you think it is an important scientific fact whether a potato or lemon is better? If not, what is the heart of what you are learning -- that's what is important, so that's what you want to focus on. Best of luck.

Regards,

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


October 27, 2009

"Everything Kids Science"
by Tom Robinson
from Abe Books
or

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Q. Hi, I am Jeri and I am a tenth grader doing my science fair project also on using fruits to conduct electricity. My proposal paper is due soon but I am confused about something. My narrowing question or purpose of conducting my experiment is to find out if the different acidity levels in the various citrus fruits-lemon, orange, grapefruit, and lime effect the voltage of electricity in a circuit to light an LED light? But my question is, is experimenting on different fruits already the dependent variables? I would think they were all controlled variables and in order to make just one dependent variable in my experiment I would need to just conduct the experiment on lemons (controlled variable in the experiment) and then for the dependent variable in some way add more lemon juice to the lemon. By using a dependent variable I would get the results to truly answer my question. If so how would I be able to add more juice to my lemons? Using a syringe maybe? I appreciate any help and hope I have not worded the question funny, or in a complicated matter. Thanks.

jeri R [last name deleted for privacy by Editor]
student - Lutz, Florida
^


October 27, 2009

A. Hi, Jeri. Yes, you are complicating things and making it hard on yourself. You said the purpose of your experiment was to find out if different acidity levels effect the voltage. Stop there for a minute -- because your "purpose" has already identified the independent and dependent variable.

The acidity level is the independent variable that you will be varying and the voltage is the dependent variable that you will be measuring. The best way to get a range of acidity levels is probably to use a range of fruits. Good luck!

But while I can understand why 3rd graders are making fruit batteries, I am a bit disappointed that, 7 years deeper into their education, 10th graders are still playing with fruit instead of conducting more controlled experiments with real reagents :-(

Regards,

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


November 11, 2009

Q. Thanks in advance. My daughter is in 5th grade and doing a science project on the electric charge and resistance in fruits and veggies. The problem is, we were under the impression that all we needed for the experiment was the fruits & veggies and multimeter. We were able to measure the electric resistance; however, we didn't get a single reading for the electric charge....are we missing something? Please help!

Candis Jackson
parent of student - Chicago, Illinois
^


November 11, 2009

A. Hi, Candis. You can measure the resistance of a fruit or vegetable by merely setting the meter to resistance mode, poking the leads of the meter into the fruit, and reading the resistance of the fruit in Ohms. Note that the resistance will vary depending on how far apart the probes are; there will be less resistance when they are close together, and more resistance when they are at the far ends of the fruit.

'Charge' is a bad term. Please don't use it as it is both wrong and misleading. You want to measure voltage. To measure this, set the meter to voltage mode, and check a flashlight battery (D cell) or a AA or AAA battery. Your TV and VCR and DVD remote controls probably all have one. Such a battery will read about 1-1/2 volts if you have set the meter correctly.

Now put a galvanized nail, or something else that is zinc into the fruit, and a penny or something that is copper into the fruit. Measure the voltage from the nail to the penny and it should be in the neighborhood of 1 volt. Best of luck.

Regards,

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



November 12, 2009

Q. Can I hook up my whole garden in series to power my house?

What happens to someone that eats the vegetables after they are done conducting electricity?

Dan Pond
- Vancouver, BC, Canada
^


November 14, 2009

A. Yes, Dan, the lower forty alone should be enough to keep a nite light going. I wouldn't eat them because they'll have copper and zinc dissolved in them, and you might become the nite light :-)

Regards,

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



December 7, 2009

Q. Hey

I'm a class 12 student and I'm doing a project on fruit cells proving to be alternatives for Leclanche cell..
I've compared the emf of various fruit cells (the fruit juice acting as the electrolyte in this case) and successfully got fair enough values of the emf

My queries are
1. I need to know the pH of the different fruit juices I used which are
a)pineapple juice
b)mixed fruit juice
c)guava juice
d)litchi juice
e)orange juice
f)mango juice
(I couldn't find a pH meter and it is difficult to look for it in 2 days!)
( I tried the pH strip but all I got is a pink colour on it!
...In all the juices)

2. I also wasn't able to find out what major acids do these fruit juices contain and how much is the acid concentration in them
(The internet couldn't provide this information :-()

Please help me !

Sanskriti N [last name deleted for privacy by Editor]
- New Delhi, India
^


December 9, 2009

A. Hi, Sanskriti. The pH will probably range from about 3.0 to 5.9. I'm sure the teacher will provide fresh pH paper of the right range and show you how to use it rather than have you guess the pH of a "mixed fruit juice". Sorry, but that kind of guessing is not science.

The use of pH paper is widespread in science projects for grades K thru 5. I don't know what "class 12" equates to in our system, but any student pursuing science classes should know how to use it; wanting to take a pass on this at this point is inappropriate. Good luck!

Regards,

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


December 28, 2009

Q. Hi my name is Victoria. If I wanted to do the same experiment, what type of electrode should I use?

Victoria C [last name deleted for privacy by Editor]
6th grader - Brooklyn, New York
^


December 29, 2009

Q. Hi my name is judy. in the circuit, could you use a different fruit, for example a red delicious apple or the granny smith apple.

judy x [last name deleted for privacy by Editor]
4th grader - Boston, Massachusetts
^


December 29, 2009

A. Hi, Victoria. Many people recommend pennies and galvanized nails as the two electrodes.

Hi, Judy. Sure you can but ... it will be both difficult to conclusively prove that one type of apple is consistently "better" than the other, and fairly inconsequential when you have done so.

Regards,

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



December 30, 2009

Q. Hello, I'm Bailey and I am doing a science project on the electricity of fruits and vegetables. I am writing a research paper with back up information. I know that fruits do not produce electricity but they provide the ions. If the acid in citrus fruits provides ions, what provides the ions in cauliflower? I have little time so please answer fast.
P.S. I'm in 6th grade.

Thanks a bunch:-)

Bailey H [last name deleted for privacy by Editor]
student - OKC, Oklahoma
^


January 13, 2010

Q. Can you use other food like strawberries?

Lauren F [last name deleted for privacy by Editor]
- Crown point, Indiana
^


January 13, 2010

A. Hi, Lauren. My hypothesis would be that you can use other foods in general and strawberries in particular. Good luck.

Regards,

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


February 12, 2010

Q. My son is doing a science fair project to answer the question "how much electricity do different foods produce?". He used a galvanized zinc and a steel nail, inserted closely together into various fruits, vegetables (and peanut butter), then used a voltmeter to measure the volts produced.

He did 5 tests of each food and got average readings of 0.46 for an orange, 0.37 for for a potato, 0.2 for the peanut butter. These seem low compared to what I've read in the posts above. What do you think is going on? And is he asking the right question? He's in grade 6.

Ray LeBlanc
- Saint John, NB, Canada
^


February , 2010

A. Hi, Ray. I'll try to fully explain things at adult level and let you explain to him the portion he needs at his level --

You can take a small amount of salt, and stir & dissolve it into water, and the salt will stay dissolved. You can stop stirring, then try pouring it through a coffee filter, but the salt will stay dissolved (in ionic form, or as ions in the water).

But you can't keep dissolving salt into the water indefinitely; rather, the water has a solubility limit for salt. After that point, the extra salt will just settle out at the bottom when you stop stirring. Not all of the salt will settle out, only the amount which is beyond the solubility limit.

Similarly, metals will dissolve into water. Generally, if the water is neither acid or alkaline, very little will dissolve. As the liquid is more strongly alkaline or more strongly acidic, it will generally hold more metal dissolved into it. Once again, there will be a solubility limit.

So at a given acid level, you can dissolve so much copper into it or so much zinc or so much iron. So let's say you've put a piece of zinc into the acid and it has dissolved as much as it can and you take the piece of zinc out. Now you put a piece of copper into the acid, what will you see happen? Nothing.

Now take some fresh acid and put the piece of copper into it. After a while, take the copper out and put a piece of zinc in. What will you see happen? The zinc will become coated with copper. The zinc wants to dissolve more strongly than the copper wants to stay dissolved. For zinc to dissolve into this acid which is already saturated with copper requires that copper be driven out of solution.

We can say that zinc is more "active" or copper is more "noble" (iron is in between these two in activity by the way). But we can actually put numbers on how much more active zinc is. Google "electrochemical series". Compared to acid or hydrogen, copper is +.3419 volts, iron is -.037 volts, and zinc is -.7618 volts.

If you put a piece of copper and a piece of zinc into a perfect acid, you will therefore read a voltage of 1.1037 volts between them. If you put a piece of zinc and a piece of iron into a perfect acid, you will read .7248 volts between them. Between a piece of copper and a piece of iron you'll get .3789 volts.

Your son's numbers are lower than the other kids' because the potential between iron and zinc is less than between copper and zinc. They sound reasonable.

As for "asking the right questions", I'm sure you realize there is some "feel goodism" designed into this experiment, with natural fruits "creating electricity", and we don't want to completely torpedo that -- so I think he's doing fine.

Regards,

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


February 14, 2010

Q. I am in eighth grade and I am doing a science fair project about fruit producing electricity, but I do not have a zinc or copper electrode, but I do have a battery tester, will that help me at all with the experiment?

Dasser Silver
- miami beach, Florida
^


February 16, 2010

A. Hi, Dasser. View the youtube video which we link to at the top of this page. I know you can find a penny to use as the copper electrode, and your mom or dad probably has a galvanized nail to use as the zinc electrode. Good luck.

Regards,

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


March 10, 2010

! Hi.

Just wanted to say I found this site by accident. I think this it is superb and I only wish that the interwebs had been around thirty-five years ago when I was doing this type of stuff at school. I might have gotten somewhere instead of banging against a brick wall and failing the final exam.

Seriously good work, and thank you so much for enabling me to finally - at age 49! - understand the principles behind the lemon battery!

Darren Lynch
- Basingstoke, Hampshire, England
^


March 10, 2010

Hi, Darren. Yes, the internet can be a terrific learning tool when people like yourself want to learn. But it can also be a tool for those who don't want to learn, enabling them to find and cut & paste answers without having to do the hard work of thinking or trying to understand the question; that's what parents, teachers, and the rest of us try to guard against :-)

Regards,

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


March 14, 2010

Q. Hello I am doing this project on how to charge electronics with fruits and vegetables and I don't have a clue on the tools or items I need. also I don't even know how to start it or any steps.

Ramon J.
student - San Francisco, California
^


March 16, 2010

A. Hi, Ramon. Please try your best to express your question in terms of the information that people have generously taken the time to make available to you on this page already. I think the "lemon battery" video doesn't leave out too much. So maybe you could pose your question in terms of what you didn't understand in that video?

Regards,

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


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