The Leyden jar at left is a device for storing static electricity. Basically, a Leyden jar is two conductors separated by an insulator. Therefore, the simplest form of a Leyden jar is tin foil on either side of a sheet of plastic as seen on the right.


Around 1750, Benjamin Franklin used more advanced Leyden jars to do his experiments. One of Franklin's Leyden jars used water and copper as conductors and a glass bottle as an insulator. 

To charge a Leyden jar, touch the top of the jar to a static generator, like the Ramsden generator shown to the right. As static electricity is produced, it flows into the Leyden jar where it is stored.

Once the Leyden jar is "charged" the static electricity will be stored until someone connects the two conductors with a wire or their hand. If the two conductors are connected, a spark will show that the charges in the water are rushing toward the charges in the copper. The static electricity flows until the Leyden jar is neutralized (an equal number of positive and negative charges in both the water and the copper).

The Circle Shock

One of Franklin's favorite experiments was the "circle shock." To try this you need a circle of people holding hands and a charged Leyden Jar. Break the circle at one point and have one of the people with a free hand hold the bottom of the Leyden jar. Then have the other person with a free hand touch the top of the Leyden jar. If there is enough electricity in the Leyden jar, everyone in the circle will feel an electric shock! Be careful as large Leyden Jars can pack quite a wallop and knock you onto the floor. Anyone with a pacemaker should not be involved in a circle of shock experiment. The circle shock does teach you how electrical in nature we truly are.

The Thunder House

Benjamin Franklin designed the thunder house to showcase the effectiveness of his invention, the lightning rod. Without the lightning rod, tall buildings were in constant threat of being struck by lighting. Franklin used his thunder house to show the disastrous effect of lighting and demonstrate how using his lighting rods could save buildings and the people within them.

The thunder house is quite simple in design. Inside the house is a can filled with flammable gasses. When static electricity is applied to the top of the house, the electricity travels down a wire to the can where it makes a spark. The spark ignites the flammable gasses and the lid of the can is blown off with enough force to knock the roof off the house. However, if a lightning rod is attached to the top of the house the static electricity is safely transported to the ground and the house is spared. The picture above is an 18^th century illustration of a thunder house in operation as well as a real house being struck by lighting. Notice how the experimenter uses a Leyden jar to provide the static electricity for the thunder house.

Lightning Rod Umbrella

The lightning rods were so successful that people wanted to make lighting rods for themselves. In fact, lighting rod apparel even became fashionable for a time.

Museum Hours: Tuesday - Saturday 10 to 5
Thursdays 10 am to  8pm 
Closed Major Holidays
Library Hours: Monday - Friday 9 to 4:30

Admission: $7 Adults; $5 Students & Seniors; Children 3 and under are FREE!

© The Bakken Updated: April 6, 2007