"Hey, Dad ...... do you have a meter that will read really small voltages and tiny amounts of current?", my son Joseph asked the other week.
"Joey, I'd better! I'm an Amateur Radio operator, and I was an electronics technician for 22 years.", I replied.
And so began the 2014 8th grade Science Fair project. My son decided to see how the pH of a fruit or vegetable would affect its ability to generate electricity. His hypothesis - the more acidic the fruit/vegetable, the more power would be generated.
The materials were an apple, a lemon, a pear and a potato. A head of red cabbage was procured to act as a pH indicator. Zinc screws and 3 inch pieces of #10 gauge copper wire served as electrodes.
Before we began generating electricity, my wife boiled some leaves from the cabbage in a pot of water. The resulting liquid would act as our litmus paper.
I stuck a screw and a piece of the copper wire into each piece of produce. The positive lead from the meter went to the copper wire and the negative lead was attached to the zinc screw. We measured both voltage and current, to be able to calculate Watts.
A teaspoon of the cabbage water was put into four glasses. Juice from each piece of produce went into the purple cabbage water. If the cabbage water turned blue, it would indicate a base. If the water stayed purple, the pH would be neutral. An acidic pH would turn the cabbage juice pink.
From lowest output to highest were - potato, pear, apple, lemon.
And in turn, the potato had the lowest pH, while the lemon had the highest. The voltage and current readings followed the pH indications. It seems my son's hypothesis was correct!
Now all Joey has to do is make a graph, print out the pictures we took and write up an explanation of what was observed. The really neat thing was that he had a good time and really enjoyed himself. I'm not sure what he wants to be, someday; but something in the scientific or electronics field would not be so bad.
72 de Larry W2LJ
QRP - When you care to send the very least!