PROJECT 15

PENNY BATTERY

This isn’t a practical project, but it is a practical bit of knowledge to keep in the back of your head.

What we are making today is voltaic piles out of pennies, zinc coated washers, and bits of paper.

Each cell consisting of a penny, a washer, and a small square of wet paper produces up to about 0.8 volts, and you can stack multiple cells to create higher voltages.

I have done this with after-school groups with kids in kindergarten to fifth grade (with various depth of explanation) and it is very useful to introduce chemistry and the fun of DIY.

Some people use 1982–present pennies that have the copper coating sanded off as the zinc, but since it is illegal to deface US currency, I use zinc washers (well . . . to be honest I use zinc washers because it is MUCH easier).

If you want to do anything slightly resembling useful, you will need at least five cells. It would take a pile about the size of your living room and five feet tall to actually run your home, so lighting up a LED or sounding a small piezo electric buzzer are about the limits of this tech.

I have found more than five cells starts to get unwieldy, and trying to use electric tape to hold it together has stymied the video for some time—maybe using a plastic coin roll, or a length of plastic pipe may make this project easier.

A cell like this will only work about six hours or so, but it does show the potential to use chemistry knowledge to do useful work.

The Materials

Material:

•   Pennies (or 1-inch copper strips cut into squares)

•   Zinc washers

•   Thin cardboard (I use old business cards)

•   Vinegar

Tools:

•   Wire

•   Small light or buzzer

•   Scissors to cut cardboard (optional)

•   Tape (optional)

•   Cup (optional)

Procedure:

Cut cards into squares and soak in vinegar

1.     Rip up a piece of thin cardboard (I use business cards, but something like a cereal box would probably work) into squares the approximately the size of a penny but slightly larger.

2.     Soak the squares in vinegar or lemon juice.

Layer Penny, Paper, Zinc

3.     Layer in the following sequence:

3.1.   Penny

3.2.   Soaked Paper

3.3.   Zinc

Multiple cells will make a volt meter move

4.     This makes one cell. To make useable voltage, stack more cells on top of each other until you can use the wires to light a small bulb or make a small buzzer sound.

Lessons Learned:

This project teaches that science is useful and can be fun. In my experience most kids like school until social convention teaches them that they should not like it.

I figured out early on that I learned better when I knew why I had to learn something. Trigonometry or chemistry was not fun if it was taught as things I needed to remember for a test, but were awesome when I realized that I could take that knowledge to DO things.