Science Buddies: "Ask an Expert"

Hello,

My son (5th grade) is doing a Veggie Power project for his science fair. His question is
"What produce requires the least amount (in mass) to make a battery that lasts the longest?".
His hypothesis is that the citrus produce will make the best battery. When he set up the trials
using Lemons, Oranges and Potatoes one week ago, we saw that potatoes required the least
amount (in mass) to light up a 2.6V LED.. THe trial is still going on and all the LEDs are still ON.
We are waiting for LEDs to go OFFto see which one lasted longest.

We want to understand that why potatoes reqd the least amount to light up LED compare to
Oranges and Lemons.. We need some help to reason this out in the conclusion..
Please advice.

thanks
Atipra

Hello and welcome to the forums:

There appears to be some controversy on why potatoes make the best batteries (see here(http://van.physics.illinois.edu/qa/listing.php?id=2390) for a discussion.)

I also found potatoes are better than citrus fruits. Let us know if you find a definitive answer!
Keith

Hello Keith,

We have already visited the site you suggested to refer. Unfortunately that too doesn't tell
exactly why potatoes make the better battey than citrus fruit.

Hope anybody else has an idea!!

thanks
Arpita

Hi Arpita,

I would suggest that you and your son research how and why potato and citrus batteries work. I think this will help you determine what you are seeing in the results of your experiment.

As a starting point, potato and citrus batteries work because of the acid in the produce (phosphoric acid in the potato and citric acid in the lemon/oranges).

Good luck!

Audrey