These jars are also called Leyden's Death Jars because they killed not only their creator, but several other people as well. These jars are made by taking a jar made of some sort of non-conductive material and coating the outside and inside with tinfoil, taking care so that at no point the outside and inside tin foil meets. For best results the ends of the tin foil should be several inches away from each other. A non-conductive jar then had a metal rod with a brass top and a metal wire long enough to reach the bottom.

These jars work by attracting electrons using the brass top when put into a magnetic field. The magnetic field can be provided by a generator that puts electrons in to the atmosphere, or a natural field created during thunder storms. The electrons travel down the top through a dangeling wire that touches the tin foil covered bottom of the jar. Here the electrons are stored until they can be discharged. The tin foil on the outside is what helps to make it an actual capacitor as it keeps the electrons from simply leaving the object, it acts as a barrier so that only when the inside metal and outside metal meet in a circuit will the charge be dispelled.

Leyden's Jars can hold enough electricity to rival that of a small lightning bolt. Leyden's jars are completely harmless if treated correctly but can be harmful or even fatal when discharged after being filled. The best way to avoid being harmed by one of the death jars is to simply leave it without a top. This ensures that no electrons are submitted into the object. It is also perfectly fine to leave one of these jars with the top ajar so that the opening is not covered. This is only effective if the top of the jar is NOT grounded.

No matter how the jar is positioned, top on or off, grounded or not the jar will never ever cause harm if held the right way. What makes this jar dangerous is the discharge of electrons. The only way to discharge the jar is too complete the circuit allowing the electrons to flow through an intermediate object and become grounded.

If the jar is only held around the middle where the tin foil is then the holder is safe because the electrons inside can't get out. <\p>

If one touches the top of the jar, similarly the loop is not complete and the jar will do nothing.

Under No Circumstances, no matter how safe you think you are being, never touch the top of the jar and the middle when the jar is assembled. This releases the charge and can cause death.

A physics teacher at my school once showed his class a Leyden's jar after using a Van de Graaff generator all hour. The jar had been sitting with the top askew, but resting on a faucet that was grounded. Unbeknownst to him it had been collecting lots of electrons from the generator. He decided that while he had the jar in class he should explain its potential for harm. He placed the lid firmly on the jar, explained what it was and said, "Now never touch the jar like this....". A streak of electricity shot from the top of the jar and into him. Fortunately since the top had not been fully resting on the jar he was only unconscious for 10 minutes, but we all learned our lesson.

Please, for the love of all that is good and holy PLEASE DO NOT build your own Leyden jar using these instructions. It's all fun and games until there is a hot dry day and you are getting shocked by everything you touch and your Mother decides to clean your room and picks up the jar the wrong way! (OK so for most of us it'll probably be a roommate instead of a Mom, but you get the picture.)

In my own experiments, I have concocted the perfect way to build a Leyden jar on a small scale so that its capacitance is limited to a charge that is not large enough to kill, although it will make the average arm twitch rather strongly.

I took one plastic spice shaker about four inches tall and coated the outside in tin foil. I then filled the inside with water. To charge up the capacitor, I use my Wimshurst machine, placing one lead in the water and turning the other so it is nowhere near the jar. I used to have a small metal rod in the plastic lid of the jar which functioned as the bridge to the water for easier charging. This rod, however, acted as a lightning rod and leaked away much of the charge when left standing and ungrounded.

Once the water is charged, the capacitor can be set on any ungrounded surface such as a wooden desk for substantially longer than the design of Leyden jar with the rod and maintains its charge. Mine still delivered an arm-twitching jolt after sitting overnight.

The interesting part about the water leyden jar is that the water inside undergoes electrolysis and slowly is converted to hydrochloric acid thanks to the chlorine in the tap water.

NOTE: Not recommended for people with chronic heart trouble or pacemakers.

The Leyden jar is an early form of the electronic device now known as a capacitor and once known as a condenser. Its function is to store an electrical charge (or technically, a charge differential) for later release. The development of such a system was naturally of great interest to early experimenters with electricity, as it provided a practical and reliable way to bottle the object of their study.

A classical design for a Leyden jar follows. Begin with a glass jar. Coat the inner and outer surfaces either with metal foil or with a thin metal layer cast directly onto the glass. Cap the jar with an insulating lid transfixed by a metal rod. Connect the inner end of the rod to the jar's inner surface (with a metal chain, for example), and at the other end of the rod affix a convenient terminal such as a metal ball. Charge the jar by bringing the terminal into contact with an electrostatic generator (a Van de Graaff generator or one of its technological predecessors). Discharge the jar by connecting the terminal to the outer metal surface, by way of any creatures or apparatus involved in your experiment.

Using modern theories of electricty, we can abstract the construction of the Leyden jar very simply: it is a capacitor comprised of two coaxial cylindrical conductors separated by a glass dielectric. That the dielectric originally took the form of a jar was simply a matter of convenience, and was incidental to the function of the device. Very crude calculation using this model shows that one can easily attain capacitance on the order of 10-9 Farads (that is, nanoFarads).

The basic idea of the Leyden jar was conceived independently by Ewald von Kleist in 1745 and Pieter van Musschenbroek in 1746; the latter was more widely credited with the invention, to the point that it was named for his hometown of Leiden, Holland (the name was later anglicized to Leyden). His original discovery involved a jar filled with water in lieu of a metal inner surface, and was discharged to earth ground rather than the local ground of an outer surface; the use of metal surfaces was advanced soon after, and significantly improved the jar's efficiency.

For verification, and additional electrical history, consider visiting the IEEE Virtual Museum at Comments welcome. Thanks to ponder for settling the Leiden/Leyden point.

Ley"den jar" (?), Ley"den phi"al (?), Elec.

A glass jar or bottle used to accumulate electricity. It is coated with tin foil, within and without, nearly to its top, and is surmounted by a brass knob which communicates with the inner coating, for the purpose of charging it with electricity. It is so named from having been invented in Leyden, Holland.


© Webster 1913.

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