There is nothing more annoying than a greedy roommate. It's absolutely infuriating to wake up and find the cookies your mother just made for you gone without a trace. Your favorite drink is empty and the homemade meal you worked so hard on the night before is nowhere to be found. This irked me so much that I made this shocking cookie jar. When a cookie burglar touches the side and the lid of the jar simultaneously, a small electric shock stops them in their tracks.
- Aluminum foil
- Stranded wire
- Plastic container with lid
I tried many different containers. Large ones are the best. Anything with ridges on the sides makes it difficult to keep the aluminum foil flat against the jar surface.
Step 1 Attach Foil
Take a sheet of tinfoil and fold it over so that it's double thick. Measure and cut the sheet to the height of the jar. Wrap the foil around the jar snugly and tape it down on the ends so it remains in place. Your jar should look like a cylinder of aluminum foil. It can help to roll the jar up in the foil like a burrito.
Duct tape blends in well with the foil.
Repeat this step for the inside of the jar—including the bottom.
Step 2 Attach Wires
If your jar has a metal cap, file off some of the inside film to expose the metal surface. Anything sharp will do. Be sure to expose the shiny conductive metal.
Strip a piece of stranded electrical wire and fray the edges out. Keeping the strands apart will increase the surface area of your electrical contact.
Tape the wire to the shiny area on the inside of the lid. A wide piece of tape ensures the contact will stay strong.
Strip the other end of the wire and tape it to the foil inside the jar. Note that in the photograph below, the foil covering the bottom of the jar had not been attached yet. Yours should already be there.
Your shocking Leyden jar is now complete. Screw the cap back on and prepare to apply the electrical charge.
My jar still smells of relish. Clean yours thoroughly.
Step 3 Charge It Up
To charge up your jar, turn on a CRT monitor or television and scrape the lid against the screen for a few seconds. Cathode ray tubes (CRTs) are those bulky pre-flat screen monitors. They contain an electron gun that fires at a chemically reactive screen to create images. Luckily for us, all of those traveling electrons create some monster static electricity.
The jar gains charge from the static electric field on the TV screen. Look close and you can see the individual pixels activated by the electron gun.
Step 4 Shock!
After the jar is charged, simply hold it by the outside foil and touch the metal cap. You will feel a shock! A bigger jar means a bigger shock. I made this cookie jar for guarding cookies from greedy roommates. Now I have to develop ones for my drinks and leftover meals.
The body is made from a plastic CD spindle. The open bottom and smooth surface made this great for attaching aluminum foil.
The cap is made from a coffee can lid, tin foil, and duct tape. Just make sure that there is no aluminum foil from the lid coming in contact with the foil on the actual jar when you place it on.
Set up your cookie jar in the living room and put your roommates' favorite food labels on the jar. If you do it often enough, you can psychologically condition them to fear your food. You could even write your name with a Sharpie on random objects that can shock them. After a few weeks, anything with your name on it will be avoided like the plague.
The static electricity from the CRT television builds up inside the cookie jar. Because the plastic container cannot conduct the current, the charge has no choice but to wait until your poor, soon-to-be shocked fingers connect the circuit between the two layers of aluminum.
This project is great for learning about electronics and is easy enough to do right this afternoon! Friends, family, acquaintances, total strangers—everyone loves getting shocked. Set up your own cookie jar at home and film your unsuspecting loved ones zapping themselves in the name of Mad Science! Post your videos to the corkboard and tell about your experience in the forum so we can all learn from each other.