A Leyden jar (or Leiden jar, or archaically, sometimes Kleistian jar) is an
electrical component
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not ...
that stores a high-voltage
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
(from an external source) between
electrical conductor
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gener ...
s on the inside and outside of a glass jar. It typically consists of a glass jar with metal foil cemented to the inside and the outside surfaces, and a metal terminal projecting vertically through the jar lid to make contact with the inner foil. It was the original form of
capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
(also called a ''condenser'').
Its invention was a discovery made independently by German cleric
Ewald Georg von Kleist
A member of the von Kleist family, Ewald was born in Wicewo (Wicewo) in Farther Pomerania. He studied jurisprudence at the University of Leipzig and the University of Leyden and may have started his interest in electricity at the latter universit ...
on 11 October 1745 and by Dutch scientist
Pieter van Musschenbroek
Pieter van Musschenbroek (14 March 1692 – 19 September 1761) was a Dutch scientist. He was a professor in Duisburg, Utrecht, and Leiden, where he held positions in mathematics, philosophy, medicine, and astronomy. He is credited with the inven ...
of
Leiden
Leiden (; in English and archaic Dutch also Leyden) is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 119,713, but the city forms one densely connected agglomeration wit ...
(Leyden), Netherlands in 1745–1746.
The Leyden jar was used to conduct many early experiments in electricity, and its discovery was of fundamental importance in the study of
electrostatics
Electrostatics is a branch of physics that studies electric charges at rest (static electricity).
Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber ...
. It was the first means of accumulating and preserving electric charge in large quantities that could be discharged at the experimenter's will, thus overcoming a significant limit to early research into electrical conduction. Leyden jars are still used in education to demonstrate the principles of electrostatics.
History
![Leidse flessen Museum Boerhave december 2003 2](https://upload.wikimedia.org/wikipedia/commons/2/22/Leidse_flessen_Museum_Boerhave_december_2003_2.jpg)
The
Ancient Greeks
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...
already knew that pieces of
amber
Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In Ma ...
could attract lightweight particles after being rubbed. The amber becomes electrified by the
triboelectric effect
The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after they are separated from a different material with which they were in contact. Rubb ...
, mechanical separation of charge in a
dielectric material
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mater ...
. The Greek word for amber is ἤλεκτρον ("ēlektron") and is the origin of the word "electricity".
Thales of Miletus
Thales of Miletus ( ; grc-gre, Θαλῆς; ) was a Greek mathematician, astronomer, statesman, and pre-Socratic philosopher from Miletus in Ionia, Asia Minor. He was one of the Seven Sages of Greece. Many, most notably Aristotle, regarded ...
, a
pre-Socratic philosopher
Pre-Socratic philosophy, also known as early Greek philosophy, is ancient Greek philosophy before Socrates. Pre-Socratic philosophers were mostly interested in cosmology, the beginning and the substance of the universe, but the inquiries of thes ...
is thought to have accidentally commented on the phenomena of electrostatic charging, due to his belief that even lifeless things have a soul in them, hence the popular analogy of the spark.
Around 1650,
Otto von Guericke
Otto von Guericke ( , , ; spelled Gericke until 1666; November 20, 1602 – May 11, 1686 ; November 30, 1602 – May 21, 1686 ) was a German scientist, inventor, and politician. His pioneering scientific work, the development of experimental me ...
built a crude
electrostatic generator
An electrostatic generator, or electrostatic machine, is an electrical generator that produces ''static electricity'', or electricity at high voltage and low continuous current. The knowledge of static electricity dates back to the earliest ci ...
: a
sulphur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
ball that rotated on a shaft. When Guericke held his hand against the ball and turned the shaft quickly, a static
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...
built up. This experiment inspired the development of several forms of "friction machines", that greatly helped in the study of electricity.
The Leyden jar was effectively discovered independently by two parties: German deacon
Ewald Georg von Kleist
A member of the von Kleist family, Ewald was born in Wicewo (Wicewo) in Farther Pomerania. He studied jurisprudence at the University of Leipzig and the University of Leyden and may have started his interest in electricity at the latter universit ...
, who made the first discovery, and Dutch scientists
Pieter van Musschenbroek
Pieter van Musschenbroek (14 March 1692 – 19 September 1761) was a Dutch scientist. He was a professor in Duisburg, Utrecht, and Leiden, where he held positions in mathematics, philosophy, medicine, and astronomy. He is credited with the inven ...
and Andreas Cunaeus, who figured out how it worked only when held in the hand.
The Leyden jar is a
high-voltage
High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, ''high voltage'' refers to voltage above a certain threshold. Equipment and Electrical conductor, conductors that carry high ...
device; it is estimated that at a maximum the early Leyden jars could be charged to 20,000 to 60,000
volts
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defini ...
. The center rod
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
has a metal ball on the end to prevent leakage of the charge into the air by
corona discharge
A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor (material), conductor carrying a high voltage. It represents a local region where the air (or other fluid) has undergone e ...
. It was first used in
electrostatics
Electrostatics is a branch of physics that studies electric charges at rest (static electricity).
Since classical times, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber ...
experiments, and later in high-voltage equipment such as
spark-gap radio transmitters and
electrotherapy
Electrotherapy is the use of electrical energy as a medical treatment. In medicine, the term ''electrotherapy'' can apply to a variety of treatments, including the use of electrical devices such as deep brain stimulators for neurological dise ...
machines.
Von Kleist
Ewald Georg von Kleist
A member of the von Kleist family, Ewald was born in Wicewo (Wicewo) in Farther Pomerania. He studied jurisprudence at the University of Leipzig and the University of Leyden and may have started his interest in electricity at the latter universit ...
discovered the immense storage capability of the Leyden jar while working under a theory that saw electricity as a fluid, and hoped a glass jar filled with alcohol would "capture" this fluid. He was the
deacon
A deacon is a member of the diaconate, an office in Christian churches that is generally associated with service of some kind, but which varies among theological and denominational traditions. Major Christian churches, such as the Catholic Churc ...
at the cathedral of Camin in
Pomerania
Pomerania ( pl, Pomorze; german: Pommern; Kashubian: ''Pòmòrskô''; sv, Pommern) is a historical region on the southern shore of the Baltic Sea in Central Europe, split between Poland and Germany. The western part of Pomerania belongs to ...
, a region now divided between Germany and Poland.
In October 1745, von Kleist tried to accumulate electricity in a small medicine bottle filled with alcohol with a nail inserted in the cork. He was following up on an experiment developed by
Georg Matthias Bose
Georg Matthias Bose (22 September 1710 – 17 September 1761), also known as Mathias Bose, was a famous electrical experimenter in the early days of the development of electrostatics. He is credited with being the first to develop a way of tem ...
where electricity had been sent through water to set alcoholic spirits alight. He attempted to charge the bottle from a large prime conductor (invented by Bose) suspended above his friction machine.
Von Kleist knew that the glass would provide an obstacle to the escape of the "fluid", and so was convinced that a substantial electric charge could be collected and held within it. He received a significant shock from the device when he accidentally touched the nail through the cork while still cradling the bottle in his other hand. He communicated his results to at least five different electrical experimenters, in several letters from November 1745 to March 1746, but did not receive any confirmation that they had repeated his results, until April 1746.
Polish-Lithuanian physicist
Daniel Gralath learned about von Kleist's experiment from seeing von Kleist's letter to
Paul Swietlicki, written in November 1745. After Gralath's failed first attempt to reproduce the experiment in December 1745, he wrote to von Kleist for more information (and was told that the experiment would work better if the tube half-filled with alcohol was used). Gralath (in collaboration with ) succeeded in getting the intended effect on 5 March 1746, holding a small glass medicine bottle with a nail inside in one hand, moving it close to an electrostatic generator, and then moving the other hand close to the nail. Von Kleist didn't understand the significance of his conducting hand holding the bottle — and both he and his correspondents were loath to hold the device when told that the shock could throw them across the room. It took some time before von Kleist's student associates at Leyden worked out that the hand provided an essential element.
Musschenbroek and Cunaeus
The Leyden jar's invention was long credited to
Pieter van Musschenbroek
Pieter van Musschenbroek (14 March 1692 – 19 September 1761) was a Dutch scientist. He was a professor in Duisburg, Utrecht, and Leiden, where he held positions in mathematics, philosophy, medicine, and astronomy. He is credited with the inven ...
, the physics professor at
Leiden University
Leiden University (abbreviated as ''LEI''; nl, Universiteit Leiden) is a Public university, public research university in Leiden, Netherlands. The university was founded as a Protestant university in 1575 by William the Silent, William, Prince o ...
, who also ran a family
foundry
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal into a mold, and removing the mold material after the metal has solidified as it cools. The most common metals pr ...
which cast
brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
cannonettes, and a small business (''De Oosterse Lamp'' – "The Eastern Lamp") which made
scientific
Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earliest archeological evidence for ...
and
medical instruments for the new university courses in physics and for scientific gentlemen keen to establish their own
'cabinets' of curiosities and instruments.
Ewald von Kleist is credited with first using the
fluid analogy for electricity and demonstrated this to Bose by drawing sparks from water with his finger.
Like von Kleist, Musschenbroek was also interested in, and attempting to repeat, Bose's experiment. During this time, Andreas Cunaeus, a lawyer, learned about this experiment from Musschenbroek, and attempted to duplicate the experiment at home with household items.
Unaware of the "Rule of
Dufay", that the experimental apparatus should be insulated, Cunaeus held his jar in his hand while charging it, and was thus the first to discover that such an experimental setup could deliver a severe
shock
Shock may refer to:
Common uses Collective noun
*Shock, a historic commercial term for a group of 60, see English numerals#Special names
* Stook, or shock of grain, stacked sheaves
Healthcare
* Shock (circulatory), circulatory medical emergen ...
.
[ He reported his procedure and experience to Swiss-Dutch ]natural philosopher
Natural philosophy or philosophy of nature (from Latin ''philosophia naturalis'') is the philosophical study of physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior throu ...
Jean-Nicolas-Sebastian Allamand, Musschenbroek's colleague. Allamand and Musschenbroek also received severe shocks. Musschenbroek communicated the experiment in a letter from 20 January 1746 to French entomologist René Antoine Ferchault de Réaumur
René Antoine Ferchault de Réaumur (; 28 February 1683, La Rochelle – 17 October 1757, Saint-Julien-du-Terroux) was a French entomologist and writer who contributed to many different fields, especially the study of insects. He introduced t ...
, who was Musschenbroek's appointed correspondent at the Paris Academy
The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at th ...
. Abbé Jean-Antoine Nollet read this report, confirmed the experiment, and then read Musschenbroek's letter in a public meeting of the Paris Academy in April 1746[ (translating from Latin to French).
Musschenbroek's outlet in France for the sale of his company's 'cabinet' devices was the Abbé Nollet (who started building and selling duplicate instruments in 1735). Nollet then gave the electrical storage device the name "Leyden jar" and promoted it as a special type of flask to his market of wealthy men with scientific curiosity. The "Kleistian jar" was therefore promoted as the ''Leyden jar'', and as having been discovered by ]Pieter van Musschenbroek
Pieter van Musschenbroek (14 March 1692 – 19 September 1761) was a Dutch scientist. He was a professor in Duisburg, Utrecht, and Leiden, where he held positions in mathematics, philosophy, medicine, and astronomy. He is credited with the inven ...
and his acquaintance Andreas Cunaeus. Musschenbroek, however, never claimed that he had invented it,[ and some think that Cunaeus was mentioned only to diminish credit to him.
]
Further developments
Within months after Musschenbroek's report about how to reliably create a Leyden jar, other electrical researchers were making and experimenting with their own Leyden jars. One of his expressed original interests was to see if the total possible charge could be increased.
Johann Heinrich Winckler
Johann Heinrich Winckler (12 March 1703 – 18 May 1770) was a German physicist and philosopher.
Biography Early life
Winckler was born in Wingendorf, a village in Silesia.Klemme, Heiner F; Kuehn, Manfred. (2016). ''The Bloomsbury Dictionary of E ...
, whose first experience with a single Leyden jar was reported in a letter to the Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
on 29 May 1746, had connected three Leyden jars together in a kind of electrostatic battery on 28 July 1746. In 1746, Abbé Nollet
Jean-Antoine Nollet (; 19 November 170025 April 1770) was a French clergyman and physicist who did a number of experiments with electricity and discovered osmosis. As a deacon in the Catholic Church, he was also known as Abbé Nollet.
Biography
...
performed two experiments for the edification of King Louis XV
Louis XV (15 February 1710 – 10 May 1774), known as Louis the Beloved (french: le Bien-Aimé), was King of France from 1 September 1715 until his death in 1774. He succeeded his great-grandfather Louis XIV at the age of five. Until he reached ...
of France, in the first of which he discharged a Leyden jar through 180 royal guardsmen
A royal guard is a group of military bodyguards, soldiers or armed retainers responsible for the protection of a royal person, such as the emperor or empress, king or queen, or prince or princess. They often are an elite unit of the regular ar ...
, and in the second through a larger number of Carthusian monks; all of whom sprang into the air more or less simultaneously. The opinions of neither the king nor the experimental subjects have been recorded.
Daniel Gralath reported in 1747 that in 1746 he had conducted experiments with connecting two or three jars, probably in series
Series may refer to:
People with the name
* Caroline Series (born 1951), English mathematician, daughter of George Series
* George Series (1920–1995), English physicist
Arts, entertainment, and media
Music
* Series, the ordered sets used in ...
.
In 1746-1748, Benjamin Franklin
Benjamin Franklin ( April 17, 1790) was an American polymath who was active as a writer, scientist, inventor, statesman, diplomat, printer, publisher, and political philosopher. Encyclopædia Britannica, Wood, 2021 Among the leading inte ...
experimented with charging Leyden jars in series, and developed a system involving 11 panes of glass with thin lead plates glued on each side, and then connected together. He used the term "electrical battery" to describe his electrostatic battery in a 1749 letter about his electrical research in 1748. It is possible that Franklin's choice of the word ''battery'' was inspired by the humorous wordplay at the conclusion of his letter, where he wrote, among other things, about a salute to electrical researchers from a battery of guns
A gun is a ranged weapon designed to use a shooting tube (gun barrel) to launch projectiles. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns/cannons, spray guns for painting or pressure washing, ...
. This is the first recorded use of the term ''electrical battery''. The multiple and rapid developments for connecting Leyden jars during the period 1746–1748 resulted in a variety of divergent accounts in secondary literature about who made the first "battery" by connecting Leyden jars, whether they were in series or parallel, and who first used the term "battery". The term was later used for combinations of multiple electrochemical cells, the modern meaning of the term "battery".
The Swedish physicist, chemist and meteorologist, Torbern Bergman
Torbern Olaf (Olof) Bergman (''KVO'') (20 March 17358 July 1784) was a Swedish chemist and mineralogist noted for his 1775 ''Dissertation on Elective Attractions'', containing the largest chemical affinity tables ever published. Bergman was the ...
translated much of Benjamin Franklin's writings on electricity into German and continued to study electrostatic properties.
Starting in late 1756, Franz Aepinus
Franz Ulrich Theodor Aepinus (13 December 172410 August 1802) was a German mathematician, scientist, and natural philosopher residing in the Russian Empire. Aepinus is best known for his researches, theoretical and experimental, in electricity a ...
, in a complicated interaction of cooperation and independent work with Johan Wilcke
Johan Carl Wilcke was a Swedish physicist.
Biography
Wilcke was born in Wismar, son of a clergyman who in 1739 was appointed second pastor of the German Church in Stockholm. He went to the German school in Stockholm and enrolled at the Univers ...
, developed an "air condenser", a variation on the Leyden jar, by using air rather than glass as the dielectric. This functioning apparatus, without glass, created a problem for Benjamin Franklin's explanation of the Leyden jar, which maintained that the charge was located in the glass.
Beginning in the late 18th century it was used in the Victorian medical field of electrotherapy
Electrotherapy is the use of electrical energy as a medical treatment. In medicine, the term ''electrotherapy'' can apply to a variety of treatments, including the use of electrical devices such as deep brain stimulators for neurological dise ...
to treat a variety of diseases by electric shock. By the middle of the 19th century, the Leyden jar had become common enough for writers to assume their readers knew of and understood its basic operation. Around the turn of the century it began to be widely used in spark-gap transmitter
A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark."Radio Transmitters, Early" in Spark-gap transmitters were the first type of radio transmitter, and were the main type use ...
s and medical electrotherapy
Electrotherapy is the use of electrical energy as a medical treatment. In medicine, the term ''electrotherapy'' can apply to a variety of treatments, including the use of electrical devices such as deep brain stimulators for neurological dise ...
equipment. By the early 20th century, improved dielectrics and the need to reduce their size and undesired inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the ...
and resistance for use in the new technology of radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
caused the Leyden jar to evolve into the modern compact form of capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
.
Design
A typical design consists of a glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...
jar with conducting tin foil coating the inner and outer surfaces. The foil coatings stop short of the mouth of the jar, to prevent the charge from arcing between the foils. A metal rod electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
projects through the nonconductive stopper at the mouth of the jar, electrically connected by some means (usually a hanging chain) to the inner foil, to allow it to be charged. The jar is charged by an electrostatic generator
An electrostatic generator, or electrostatic machine, is an electrical generator that produces ''static electricity'', or electricity at high voltage and low continuous current. The knowledge of static electricity dates back to the earliest ci ...
, or other source of electric charge, connected to the inner electrode while the outer foil is grounded. The inner and outer surfaces of the jar store equal but opposite charges.
The original form of the device is just a glass bottle partially filled with water, with a metal wire passing through a cork closing it. The role of the outer plate is provided by the hand of the experimenter. Soon John Bevis
John Bevis (10 November 1695 in Salisbury, Wiltshire – 6 November 1771) was an English doctor, electrical researcher and astronomer. He is best known for discovering the Crab Nebula in 1731. He was educated at Christ Church, Oxford, bein ...
found (in 1747) that it was possible to coat the exterior of the jar with metal foil, and he also found that he could achieve the same effect by using a plate of glass with metal foil on both sides. These developments inspired William Watson William, Willie, Bill or Billy Watson may refer to:
Entertainment
* William Watson (songwriter) (1794–1840), English concert hall singer and songwriter
* William Watson (poet) (1858–1935), English poet
* Billy Watson (actor) (1923–2022), A ...
in the same year to have a jar made with a metal foil lining both inside and outside, dropping the use of water.
Early experimenters (such as Benjamin Wilson in 1746) reported that the thinner the dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...
and the greater the surface, the greater the charge that could be accumulated.
Further developments in electrostatics revealed that the dielectric material was not essential, but increased the storage capability (capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
) and prevented arcing between the plates. Two plates separated by a small distance also act as a capacitor, even in a vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
.
Storage of the charge
It was initially believed that the charge was stored in the water in early Leyden jars. In the 1700s American statesman and scientist Benjamin Franklin
Benjamin Franklin ( April 17, 1790) was an American polymath who was active as a writer, scientist, inventor, statesman, diplomat, printer, publisher, and political philosopher. Encyclopædia Britannica, Wood, 2021 Among the leading inte ...
performed extensive investigations of both water-filled and foil Leyden jars, which led him to conclude that the charge was stored in the glass, not in the water. A popular experiment, due to Franklin, which seems to demonstrate this involves taking a jar apart after it has been charged and showing that little charge can be found on the metal plates, and therefore it must be in the dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...
. The first documented instance of this demonstration is in a 1749 letter by Franklin. Franklin designed a "dissectible" Leyden jar ''(right)'', which was widely used in demonstrations. The jar is constructed out of a glass cup nested between two fairly snugly fitting metal cups. When the jar is charged with a high voltage and carefully dismantled, it is discovered that all the parts may be freely handled without discharging the jar. If the pieces are re-assembled, a large spark
Spark commonly refers to:
* Spark (fire), a small glowing particle or ember
* Electric spark, a form of electrical discharge
Spark may also refer to:
Places
* Spark Point, a rocky point in the South Shetland Islands
People
* Spark (surname)
* ...
may still be obtained from it.
This demonstration appears to suggest that capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
s store their charge inside their dielectric. This theory was taught throughout the 1800s. However, this phenomenon is a special effect caused by the high voltage on the Leyden jar. In the dissectible Leyden jar, charge is transferred to the surface of the glass cup by corona discharge
A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor (material), conductor carrying a high voltage. It represents a local region where the air (or other fluid) has undergone e ...
when the jar is disassembled; this is the source of the residual charge after the jar is reassembled. Handling the cup while disassembled does not provide enough contact to remove all the surface charge. Soda glass is hygroscopic
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substan ...
and forms a partially conductive coating on its surface, which holds the charge. Addenbrooke (1922) found that in a dissectible jar made of paraffin wax, or glass baked to remove moisture, the charge remained on the metal plates. Zeleny (1944) confirmed these results and observed the corona charge transfer.
Quantity of charge
Originally, the amount of capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
was measured in number of ' jars' of a given size, or through the total coated area, assuming reasonably standard thickness and composition of the glass. A typical Leyden jar of one pint
The pint (, ; symbol pt, sometimes abbreviated as ''p'') is a unit of volume or capacity in both the imperial unit, imperial and United States customary units, United States customary measurement systems. In both of those systems it is tradition ...
size has a capacitance of about 1 nF.
Residual charge
If a charged Leyden jar is discharged by shorting the inner and outer coatings and left to sit for a few minutes, the jar will recover some of its previous charge, and a second spark can be obtained from it. Often this can be repeated, and a series of 4 or 5 sparks, decreasing in length, can be obtained at intervals. This effect is caused by dielectric absorption Dielectric absorption is the name given to the effect by which a capacitor, that has been charged for a long time, discharges only incompletely when briefly discharged. Although an ideal capacitor would remain at zero volts after being discharged, ...
.
See also
* Franklin bells
Franklin bells (also known as Gordon's Bells or lightning bells) are an early demonstration of electric charge designed to work with a Leyden jar. Franklin bells are only a qualitative indicator of electric charge and were used for simple demons ...
Notes
References
External links
Leyden Jar – Interactive Java Tutorial
National High Magnetic Field Laboratory
* Schechner, Sara
“The Art of Making Leyden Jars and Batteries according to Benjamin Franklin.”
eRittenhouse 26 (2015).
* Science fair project idea.
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