Leyden Jars

Lenny R's Film Can Leyden Jar

This is a jar made from a film canister. The original picture and how to build it are on Lenny R's web page. There's also a quick and dirty (but very effective) static generator there. 

This is one of my jars. It's made from a polyethylene food container. The ball on top has a coating (graphite) that allows a spark to travel along its surface (as well as jumping the gap). 

Nice Leyden jar

Here's a fine jar made by PV Scientific Instrument company. They make   reproductions of many classical laboratory instruments.

A Leyden jar is a device that early experimenters used to help build and store electric energy.  It was also referred to as a "condenser" because many people thought of electricity as fluid or matter that could be condensed.  Nowadays someone familiar with electrical terminology would call it a capacitor.

Basically, the Leyden jar is a cylindrical container made of a dielectric (that's an insulator, like plastic or glass) with a layer of metal foil on the inside and on the outside. With the outside surface grounded, a charge is given to the inside surface. This gives the outside an equal but opposite charge. When the outside and inside surfaces are connected by a conductor...SNAP! You get a spark and everything returns to normal.

The amount of charge one of these devices can store is related to the voltage applied to it times its capacitance. In simple terms, capacitance depends on the AREA of the foil or metal, the TYPE OF MATERIAL between the two layers of foil, and the THICKNESS (generally the thinner the better) of that material.

Check out  static tube  for a simple way to charge a Leyden jar. Another way to charge a Leyden jar, If you haven't got a high voltage generator, is to use an electrophorus.

A few pointers for constructing Leyden jars:

Here are a few more pictures of Leyden jars, and other tools:

A 1.6 pint container 

Frosting can. 

This is an electroscope. In the presence of a static charge imbalance the loosely hanging foil leaves repel each other. 

Discharge tongs

The electrode and stem from one of my Leyden jars. 

Basic Anatomy

 With some thought and research, excellent Leyden jars can be made using common materials. For those who don't have the time or resources to devote, there are people and companies that sell Leyden jars or other electrostatic related equipment.

Something to keep in mind as you digest all of this is that the length of spark an electrostatic machine can produce is not directly dependent on the capacitance of the Leyden jar connected to it.  The energy in the spark is directly related to capacitance (and voltage). In other words, I'm saying that if you want a longer spark you won't get it by just making a bigger Leyden jar. You'll get a hotter, louder, more visible spark. Learn more about, and improve, the design of your machine.  I'm no genius when it comes to the laws governing electricity, but there's one thing that I am positive about: These things get more dangerous as they get bigger.  Once again, let me say it another way: The pain a fully charged Leyden jar can inflict varies directly with its capacitance. Small ones are almost like toys, larger ones can leave you on your butt wondering what just happened. Don't fool yourself into thinking that a couple of pieces of tin foil can't be dangerous.

Don't just take my word for it, though, see what Benjamin Franklin had to say when he shocked the  #$%^&#!  out of himself.

Other simple capacitors
More info about materials to use for electrostatic experiments.
Back to the Static Generator Page