The Leyden jar – forerunner of the modern-day capacitor
The Leyden jar has been around for over 200 years and is the forerunner of the modern-day capacitor. The guy who invented it tested it on himself and stated that ‘my whole body was shaken as though by a thunderbolt’. And no, his name wasn’t Leyden – Leyden was the town that the jar was invented in. If we had named the jar after the inventor, it would be called a ‘Musschenbroeck jar’ (now you see why it’s called a Leyden jar).
A Leyden jar was once discharged through seven hundred monks who were holding hands. They flew up into the air simultaneously.
How to make a simulated Leyden jar using a plastic film can and a Styrofoam plate
By the way, you might want to try the Making Sparks – Part I experiment (or at least read it over). It explains much of what’s going on here.
- Put the lid on the film can.
- Push a nail down through the center of the lid.
- Wrap the bottom 2/3 of the file can with aluminum foil. Taping it won’t hurt anything.
- Fill the film can with water. Make sure that it’s full enough so that the nail touches the water. This is our Leyden jar. Now we need to charge it…
- Use the pliers to remove the pen cartridge from the insides of the BIC pen. This will be our ‘handle’.
- Place the pie pan upside down on the table.
- Push a thumbtack down through the center of the pie pan.
- Turn the pan back over so you are looking at the inside of the pan. The point of the thumbtack should be sticking up through the middle of the pan.
- Coat the thumbtack point with hot glue. Be careful. They don’t call it ‘hot glue’ for nothing.
- Push the bottom of pen body down onto the extending thumbtack point. You could also use a pencil for this step and press the eraser end of the pencil down onto the thumbtack.
- Let the glue dry for a little while.
- Rub the Styrofoam plate with the wool rag for about 45 seconds.
- Place a Styrofoam plate upside down on the table.
- Using the pen ‘handle’ that we just created, place the pie pan on top of the upside-down Styrofoam plate (the pen should be sticking up).
- Quickly touch the pie pan with your finger. It may produce a small shock.
- Remove the pie pan off the Styrofoam plate using the pen ‘handle’. The pan is now ‘charged’.
- Hold the Leyden jar by the aluminum foil.
- Charge the jar by touching the charged pie pan to the nail stuck through the lid of the Leyden jar. You can recharge the pie pan (by following steps 12 through 16) and add more charge to the Leyden jar over and over again.
- Now discharge the jar by touching the aluminum foil with one hand and the protruding nail with the other.
When you touch a positively charged pie pan to the nail on the Leyden jar, electrons flow from the nail onto the positive pie pan. This results in a positive charge on the nail. This positively charged nail now attracts electrons from your body onto the aluminum foil of the jar.
The Leyden jar now has a positive center and a negative outer foil which are being separated from each other by the plastic film can (which acts as an insulator). If you touch one finger to the foil and another to the center of the Leyden jar, a spark will jump as the negative charges are attracted through you to the positive nail.
Experiment supplies required for the Making Sparks Part II experiment
Supplies: Tape, Film canister, BIC pen, Pie pan, Thumbtack, Glue (hot), Styrofoam plate, Nail, Aluminum foil, Wool rag
In-Article Image CreditsLeyden_jar_showing_construction via Wikimedia Commons with usage type - Public Domain. Circa 1914
Andreas_Cunaeus_discovering_the_Leyden_jar via Wikimedia Commons with usage type - Public Domain. Circa 1886
Featured Image CreditAndreas_Cunaeus_discovering_the_Leyden_jar via Wikimedia Commons with usage type - Public Domain. Circa 1886