Ever heard of a Leyden jar? It's 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). It was once discharged through
seven hundred monks who were holding hands. They flew up into the air simultaneously.
Definitely sounds like a experiment Dad should be involved with...
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
if '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 of 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 (Hey Dad - can you come hear a sec... I need some assistance).
Now duck and watch for flying debris. Just kidding of course, but it
will make a spark.
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 chargeon
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 a 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.
Parent's Note. Leyden jar, pronounced LY duhn, was one of
the first devices used to store an electric charge. It was invented in Leiden (sometimes
spelled Leyden), the Netherlands, in 1746. A Leyden jar is a glass jar that is sealed
with a cork. Sheets of metal foil cover about half of the inside and outside of
the Leyden jar. The metal foil conducts electricity, but the glass does not. A brass
rod is inserted through the cork and brought in contact with the foil in the jar.
When the brass rod is connected to a source of electricity, currenttravels through
the rod and charges the inner foil. Current cannot pass through the glass, but the
foil on the outside becomes charged by induction if it is properly grounded. The
outer foil has a charge opposite to the charge inside the jar. When the flow of
current into the jar stops, a charge remains stored in the jar. If the inner layers
of foil and outer layers of foil are then connected by a conductor, their opposite
charges will cause a spark that discharges the jar.