How a Jar of Water Literally Shocked Thousands: How a Leyden Jar Works

Wait? How did a jar of water shock anyone?  And why?  Well, I’ll tell you and along the way I will talk about: shocking people for the kings pleasure, breaking the rules and masochistic adrenalin junkies with some really difficult names to pronounce.  Ready, lets go.

This story began on October 11, 1745.  On that date a German man named Ewald Georg von Kleist accidentally gave himself a pretty good shock. Kleist had read about a “modern wizard” named Matthias Bose who had electrified himself with an electrical machine and then used a spark from his finger to light alcohol on fire.  Now Kleist didn’t really know how Bose did it so he decided to connect the alcohol directly to the electricity machine.  He took a glass jar full of alcohol and put a cork in it.  He then put a nail through the cork into the alcohol and held it up to his electric generator.  For a long time, not much happened.  Then, Kleist touched the nail with his free hand and was thrown across the room! 

Kleist wrote to several friends about his traumatic experience and they were eager to copy it.  (The people who were studying electricity at the time were a bit of masochistic adrenalin junkies – attracted to all stories of pain – as you will see.)  However, even though Kleist reported that his device worked when being held by ones bare hands, they thought that was silly and demonstrated Kleist’s lack of electrical knowledge.  Therefore, they experimented with a jar on a wax stand and reported back that the device did not work. 

Unfortunately for Kleist’s friends (and for Kleist), the bare hand was very important part of how the bottle stored energy.  At the time they knew that if they tried to electrify a conductive material touching the ground all of the electricity would flow into the ground.  Therefore, they knew that you needed to put it on an insulator: a glass or wax or the like.  What the didn’t realize was that if the insulator was thin, with a conductor on the other side then the electricity wouldn’t flow into the ground, instead it could store a ridiculous amount of charge.

 See, when they rubbed the glass sphere on the electric machine it collected electrons.  The electrons then flowed into the liquid in the bottle.  The electrons would then stop at the inner surface of the jar, as the glass is an insulator and it does not let electrons move easily.  However, electricity works at a distance.  So, if someone is holding the glass with bare hands, then some electrons in the persons hands flows away from the jar and into the person, and eventually, the ground.  This leaves the outside of the jar with a positive charge which causes more electrons to collect on the inner surface of the jar, which causes even more electrons to flow from the outside of the jar and through the person.   This continues until it reaches it’s maximum charge capacity (which is why it is called a capacitor) with equal and opposite charges on both surfaces.  Once someone, like poor Kleist, touches both surfaces, the electrons on the inner surface would race through him all at once giving him that terrible shock. 

One of the surreal features of this jar is that it stores charge for future use.  You can charge it up with an electrical machine (or with a modern battery) and then safely move it by only touching either the outside or the nail.  The jar will keep its charge for hours and even days!  Then when you connect the outside of the jar to the nail you get a spark or a shock!

Of course, at the time they did not know any of this so all of their attempts to recreate the great shock were fruitless.  As Kleist was not famous in any way and his work was not repeatable, it looked as if nothing would come of his discovery.

Luckily, a complete amateur named Andreas Cunaeus joined the story.   Cunaeus either heard about Kliest’s experiment or came up with something strikingly similar on his own.  Either way, he had the same setup but with water instead of alcohol in the jar.  Cunaeus got a terrible shock from his jar of water just like Kliest did with his jar of alcohol.  He then ran and told his friend Pieter van Musschenbroek who was a famous Physics professor in the town of Leyden, Germany.  Musschenbroek repeated Cuneaus’s water jar experiment despite Cunaeus’s description of how it affected him.  Like Cuneaus and Kleist before him, Musshenbroek got a terrible shock too.  In fact he wrote to a Parisian friend that it was a “terrible experiment” which he advised him never to try himself.  Musshenbroek said that he wouldn’t do “it again for all the kingdom of France” and that he only “survived by the grace of God”!

A French clergyman and scientist named Jean-Antoine Nollet read the letter and was intrigued (remember, masochists), and quickly repeated the experiment whereby it “bent him double and knocked out his wind”.   Nollet then read the paper to the Paris Academy and pretty soon everyone was basically torturing each other with these jars.  Nollet began selling jars calling them “Leyden Jars” as Mucchenbroek was from the town of Leyden (and presumably Mucchenbroek jars was a mouthful).

One of the favorite activities with Leyden jars was to electrocute large groups of people, either holding hands or holding metal bars.  Nollet entertained Louis XV, the King of France, by shocking 180 soldiers at one time, over 200 monks in their robes at a monastery, and as many as six hundred people in a giant circle at the College de Navarre.  Nollet masochistically noted that, “It is singular to see the multitude of different gestures, and to hear the instantaneous exclamation of those surprised by the shock.”  In theory, these experiments informed people of how circuits worked (in a circle) and how fast electricity went (very), but it was mostly used as strange entertainment.

In 1767, a dour looking English scientist described the effect of the Leyden jar thusly: “Everybody was eager to see, and notwithstanding the terrible account that was reported of it, to feel the experiment; and in the same year in which it was discovered, numbers of persons, in almost every country in Europe, got a livelihood by going about and showing it”

Leyden jars were not only insanely popular for demonstrations they are also vital to technology even today.  See, if you want to get a large shock (like a defibrillator) then you use a modern version of a Leyden jar called a capacitor to store energy from a battery and then connect to the capacitor to get a large jolt of electricity all at once.  If, conversely, you wish to have a portable system that is protected from jolts of electricity (as you do for all modern electronics), then you add a capacitor to absorb the spike of energy.  Finally, if a charged capacitor is connected to a coil it can create oscillating signals, which is vital for radio, television and even computers and cell phones.  (I will get to this in later videos, don’t worry) 

In the 1700s, one of the things that was so intriguing about the jars (aside from their awesome power) was that they violated everything that they thought they understood about electricity. Why do you store more electricity if you let the electricity flow away from the outside of a jar?  The scientists at the time couldn’t figure it out.  As Mucchenbroek said, at the end of his first letter about the discovery of the jar,  “I’ve found out so much about electricity that I’ve reached the point where I understand nothing and can explain nothing.”  The Leyden jar was a key to unlock the mysteries of how electricity works.  Strangely enough, the person who managed to figure it out, the man who intuitively saw what was going on electrically, did not live in Germany or France or England.  Instead he lived in one of the last places scientists from Europe would expect: Philadelphia. 

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