Electricity from Lemons and Limes?

Try Googling "Lemon Battery" You will get a lot of websites.

After you have a good understanding of how to build a "Lemon Battery" the lime battery will be pretty much the same.

To determine which can produce the most electricity you can measure a few things.

1) Open circuit voltage, This is the voltage that you measure directly across the terminals with nothing else connected.

2) Output Power, connect a resistor across the terminals and measure the output voltage. Start with a 1000 ohm and reduce (or increase if needed) the value until the voltage drops by about 10% from the open circuit voltage. Output power = Voltage * Voltage / Resistance.

These are not exact methods but they should be more than enough for a young child's science project - the rest is in the presentation - that may include understanding what voltage and power are, at least to an elementary level.

Radio Shack or any electronics store can supply the components and meters you need.

The folks on Mythbusters did something like this, but with other fruits and vegetables. You might want to check out their web site and poke around a bit.

Hmmm... To produce an electricity you need to stick to the fruit couple of different conductors, say copper wire and a graphite (from pencil), or to collect juices from them to some dielectric containers (glass or plastic may be used) then put electrodes in them.

To measure voltages you will need a voltage meter.

except that the main active ingredient for a battery will be acetic acid, not vitamin C (= ascorbic acid) - this applies both to lemons and limes.

except that the main active ingredient for a battery will be acetic acid, not vitamin C (= ascorbic acid) - this applies both to lemons and limes

No, citrus fruits in their unfermented state contain no acetic acid. The sour taste in is due to citric acid.

From Wikipedia:

"Citric acid exists in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits (1.44 and 1.38 grams per ounce of the juices, respectively). The concentrations of citric acid in citrus fruits range from .005 mol/L for oranges and grapefruits to .030 mol/L in lemons and limes. These values will vary depending on the circumstances in which the fruit was grown."

http://en.wikipedia.org/wiki/Citric_acid

By contrast, acetic acid is produced synthetically, or by fermentation:

"Acetic acid is produced both synthetically and by bacterial fermentation. Today, the biological route accounts for only about 10% of world production, but it remains important for vinegar production, as the world food purity laws stipulate that vinegar used in foods must be of biological origin. About 75% of acetic acid made for use in the chemical industry is made by methanol carbonylation, explained below."

http://en.wikipedia.org/wiki/Acetic_acid

Excellent replt Albert i give you a good answer for the explanation.

There is information on the ZOOM website (a kids show on PBS).

http://pbskids.org/zoom/activities/sci/lemonbattery.html

good luck

A copper penny and a zinc coated nail work well. The more fruit the higher the voltage. With a good juicy lemon it should register about .8 volts. connect the copper to the nail from one fruit to the next to increase the voltage. The last two you connect your volt meter to.

This is a good link - the setup is very simple and all of the necessary parts are house-hold items (except for the clock). I would say that this is pretty much what monpetite is looking for.

GA

Lots of good advice from above posts.

Take a moment to reflect upon what Leveles said in posting #4. "Don't expect anything stable" is a key issue here. I suspect that the voltage difference is due to the two different metals selected and the current (power, energy, whatever) is dependent upon the ph, how wet the fruits are inside, how far apart the metals are, how much metal surface area is in contact with the fruit, etc. Thus, "our instrumentation is not good enough for us to tell the difference" is a very realistic outcome. This is not a problem, it is a feature. Teach a little about batteries and teach a little about in the real world you often have one more problem than you expected.

The most important thing is to try to make it fun and easy for the kids. I know some will disagree with this, but we teach kids to hate math and science at an early age. Make lights turn on. Maybe even make a very small motor spin. If it takes a dozen lemons then (if the connections are EASY to make work) go ahead and make a big mess. The kids should go home saying "Wow, I didn't know you could do that" and maybe even "Wow, that was fun". The 8 year olds should learn a little but be impressed a lot.

Math is a tool. Science is a tool. Engineering is the application of these tools. Make the kids want to learn how to use the tools because they want to apply them in doing something useful/fun. Don't fall into the rut of having math and science be classes that must be passed to advance to the next grade.