Franklin's electrostatic machine
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/df/Franklin_machine.jpg/240px-Franklin_machine.jpg)
on display at the Franklin Institute
Franklin's electrostatic machine is a high-voltage
Background
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Franklin%27s_Leyden_jar_experiment.png/150px-Franklin%27s_Leyden_jar_experiment.png)
Franklin was not the first to build an electrostatic generator. European scientists developed machines to generate static electricity decades earlier. In 1663, Otto von Guericke generated static electricity with a device that used a sphere of sulfur.[1] Francis Hauksbee developed a more advanced electrostatic generator around 1704 using a glass bulb that had a vacuum. He later replaced the globe with a glass tube of about 2.5 feet (0.76 m) emptied of air.[1] The glass tube was a less effective static generator than the globe, but it became more popular because it was easier to use.[2]
Machines that generated static electricity with a glass disc were popular and widespread in Europe by 1740.[3] In 1745, German cleric Ewald Georg von Kleist and Dutch scientist Pieter van Musschenbroek discovered independently that the electric charge from these machines could be stored in a Leyden jar, named after the city of Leiden in the Netherlands.[3]
In 1745, Peter Collinson, a businessman from London who corresponded with American and European scientists, donated a German "glass tube"[4] along with instructions how to make static electricity, to Franklin's Library Company of Philadelphia.[5] Collinson was the library's London agent and provided the latest technology news from Europe.[6][7][8] Franklin wrote a letter to Collinson on March 28, 1747,[9] thanking him, and saying the tube and instructions had motivated several colleagues and him to begin serious experiments with electricity.[10]
In 1746, Franklin began working on electrical experiments with Ebenezer Kinnersley after he bought all of Archibald Spencer's electrical equipment that he used in his lectures. Later, he was also associated with Thomas Hopkinson and Philip Syng in experimentation with electricity.[11][12] In the summer of 1747 they had received an electrical system from Thomas Penn.[13] While no records exists to tell exactly what parts were included in the system, historian J. A. Leo LeMay believes it was a combination of an electricity generating machine, a Leyden jar, a glass tube, and a stool that was electrically insulated from the ground.[13][14] This gave Franklin a complete system to experiment with generating and storing electricity.[7]
When
Description
Franklin's machine used a belt and pulley system that could be operated by one person turning a crank.[21] A large pulley was attached to the crank handle, and a much smaller pulley was attached to a large glass globe. An iron axle passed through the globe. This allowed the globe to be rotated at high speed.[23] When the crank was turned, the glass globe rubbed against a leather pad, which generated a large static charge, similar to the electrical charge that could be created by rubbing a glass tube with wool cloth by hand. The machine was unique improvement over others made in Europe at the time, as the glass globe could be spun faster with much less labor.[24] A few revolutions of the handle were all that were needed to charge a Leyden jar.[24][25]
The electricity produced by the machine, in the form of sparks, passed through a set of metal needles positioned close to the spinning globe. The electric charge continued passing through a beaded iron chain, which acted as a conductor, to a Leyden jar that received the electricity.[26][27][28] Franklin called the sparks produced by the machine "electrical fire".[7]
The glass globes, known as "electerizing globes",
Electrical principles
Franklin's experiments with Leyden jars progressed to connecting several Leyden jars together in a series, with "one hanging on the tail of the other". All of the jars in the series could be charged simultaneously, which multiplied the electrical effect.
Through his research, Franklin was among first to prove the electrical principal of
Several 18th-century electric terms were derived from his name. For example, static electricity was known as "Franklin current",
Lightning rod invention
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/df/Lightning_safe_study.jpg/180px-Lightning_safe_study.jpg)
Franklin invented the
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/be/Casa_del_fulmine_inv_1545_IF_41785.jpg/170px-Casa_del_fulmine_inv_1545_IF_41785.jpg)
To test his theory, Franklin proposed a potentially deadly experiment, to be performed during an electrical storm, where a person would stand on an insulated stool inside a sentry box, and hold out a long, pointed iron rod to attract a lightning bolt.[15] A similar but less dangerous version of this experiment was first performed successfully in France On May 10, 1752, and later repeated several more times throughout Europe, though after a fatality in 1753 it was less frequently tried. Franklin declared that this "sentry-box experiment" showed that lightning and electricity were one and the same.[15]
Franklin realized that wooden buildings could be protected from lightning strikes, and the deadly fires that often resulted, by placing a pointed iron on a rooftop, with the other end of the rod placed deep into the ground. The sharp point of the lightning rod would attract the electrical discharge from the cloud, and the lightning bolt would hit the iron rod instead of the wooden building. The electric charge from the lightning would flow through the rod directly into the earth, bypassing the structure, and preventing a fire.[51]
Franklin's friend Kinnersley traveled throughout the eastern United States in the 1750s demonstrating man-made "lightning" on model thunder houses to show a how an iron rod placed into the ground would protect a wooden structure. He explained that lightning followed the same principles as the sparks from Franklin's electrostatic machine. These lectures by Kinnersley were widely advertised, and were one of the ways Franklin's lightning rod was demonstrated to the general public.[52]
Legacy
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Familiar_Introduction_to_Electricity_by_Joseph_Priestly%2C_plate_7.jpg/150px-Familiar_Introduction_to_Electricity_by_Joseph_Priestly%2C_plate_7.jpg)
"electrostatic machines"
Franklin distributed copies of the electrostatic machine to many of his close associates to encourage them to study electricity.[13] Between 1747 and 1750, Franklin sent many letters to his friend Collinson in London about his experiments with the electrostatic machine and the Leyden jar, including his observations and theories on the principles of electricity.[12] These letters were collected and published in 1751 in a book entitled Experiments and Observations on Electricity.[10][53][54][55]
While Joseph Priestley was writing about the history of electricity, Franklin encouraged him to use an electrostatic machine to perform the experiments he was writing about. Priestly designed and used his own variations of Franklin's machine.[56] While replicating the electrical experiments, some unanswered questions prompted Priestly to design additional experiments, leading to additional discoveries. In 1767, he published a 700-page book on his findings called The History and Present State of Electricity.[57][58]
Eighteenth-century scientific laboratories usually contained some form of hand-operated electrostatic machine. Italian scientist
After Franklin's death, two iconic artifacts from his research, the original "battery" of Leyden jars, and the "glass tube" that was a gift from Collinson in 1747, were given to the Royal Society in 1836 by Thomas Hopkinson's grandson Joseph Hopkinson, in accordance with Franklin's will.[60]
See also
- Wistarburgh Glass Works
- Corbett's electrostatic machine
- Van de Graaff generator
References
Citations
- ^ a b Lemay 2009, p. 61.
- ^ Lemay 2009, p. 62.
- ^ a b c Grimnes 2014, p. 495.
- ^ a b c Talbott 2005, p. 185.
- ^ Cohen 1990, p. 61.
- ^ Lemay 2009, pp. 58–59.
- ^ a b c Crane 1954, p. 48.
- ^ Pasles 2008, p. 119.
- ^ Lemay 2009, p. 67.
- ^ National Historical Publications and Records Commission. Archived from the originalon 28 October 2016. Retrieved July 15, 2015.
- ^ a b Maclean 1877, p. 142.
- ^ a b c Talbott 2005, p. 182.
- ^ a b c d e Lemay 2009, p. 75.
- ^ Garche 2013, p. 596.
- ^ a b c Cohen 1990, p. 28.
- ^ a b c Talbott 2005, p. 184.
- ^ Lemay 2009, p. 71.
- ^ Waldstreicher 2005, pp. 126–127.
- ^ a b Finger 2012, p. 85.
- The Franklin Institute. 2016. Archived from the originalon January 8, 2019. Retrieved November 7, 2016.
- ^ a b Tucker 2005, p. 40.
- ^ Lemay 2009, p. 91.
- ^ Secor 1975, p. 214.
- ^ a b c Lemay 2009, p. 72.
- ^ Cohen 1956, p. 440.
- ^ McNichol 2006, pp. 10–16.
- ^ Gregory 1822, p. 8.
- ^ McGrath 2001, p. 1335.
- ^ a b Bridenbaugh 2012, p. 63.
- ^ "The Wistars and their Glass 1739 – 1777". WheatonArts. 2015. Retrieved November 7, 2016.
- ^ a b Cohen 1956, p. 460.
- ^ Lynn 2009, p. 136.
- ^ McNichol 2006, p. 16.
- ^ Malmivuo & Plonsey 1995, p. 13.
- ^ a b Morgan 2003, p. 12.
- ^ Lemay 2009, pp. 72–75.
- ^ Grimnes 2014, p. 496.
- ^ Schiffer 2003, pp. 136, 137.
- ^ "Electro-therapeutics". The Encyclopedia Americana: A universal reference library comprising the arts and sciences. Scientific American Compiling Department. 1905.
- ^ Coulson 1950, p. 32.
- ^ LeMay 1987, p. 600.
- ^ a b Isaacson 2004, pp. 137–145.
- ^ Lemay 2009, pp. 86–96.
- ^ Isaacson 2004, p. 141.
- ^ Franklin, Benjamin (October 19, 1752). "The Kite Experiment". The Pennsylvania Gazette. Archived from the original on September 22, 2010.
- ^ "Kite Experiment". Benjamin Franklin Historical Society. Retrieved March 1, 2022.
- ^ Tucker 2005.
- ^ Matthews 2003.
- ^ Schiffer 2004.
- ^ Boese 2015.
- ^ Schafer 1992, p. 58.
- ^ Talbott 2005, p. 188.
- ^ McNichol 2006, p. 19.
- ^ Franklin 1751.
- ^ Cohen 1956, pp. 432, 478.
- ^ Pyenson & Gauvin 2002, p. 93.
- ^ Jackson 2005, pp. 64–66.
- ^ Schofield 1997, pp. 140–150.
- ^ Avery 2016, p. 207.
- ^ Cohen 1956, p. 454B.
Sources
- Avery, John Scales (2016). Science and Society. ISBN 978-981-3147-73-7.
- Boese, Alex (2015). "The Electric Kite Hoax". The Museum of Hoaxes. Retrieved February 6, 2017.
- Bridenbaugh, Carl (2012). The Colonial Craftsman. ISBN 978-0-486-14473-3.
- Cohen, I. Bernard (1956). Franklin and Newton: An Inquiry Into Speculative Newtonian Experimental Science and Franklin's Work in Electricity as an Example Thereof. Harvard University Press.
- Cohen, I. Bernard (1990). Benjamin Franklin's Science. ISBN 978-0-674-06659-5.
Peter Collinson glass tube Franklin gift.
- Coulson, Thomas (1950). Joseph Henry: His Life and Work. Princeton University Press.
The atmosphere of Philadelphia gave him and his associates exceptional opportunity to exercise their skill with the electrostatic machine. As a result, many of their experiments were of an original character. The famous kite experiment enabled the Philadelphia group to established what had been surmised by others, that lightning was identical to the mild charge of electricity produced by the friction of the electrostatic machine. Franklin invented the lightning rod, which goes down in history as the first practical electrical invention.
- Crane, Verner Winslow (1954). Benjamin Franklin and a Rising People. Little, Brown and Company.
- Finger, Stanley (2012). Doctor Franklin's Medicine. ISBN 978-0-8122-0191-8.
- Franklin, Benjamin (1751). "Experiments and Observations on Electricity". Smithsonian Libraries.
- Garche, Jürgen (2013). Encyclopedia of Electrochemical Power Sources. ISBN 978-0-444-52745-5.
- Gregory, George (1822). A Dictionary of Arts and Sciences. Collins and Company.
- Grimnes, Sverre (2014). Bioimpedance and Bioelectricity Basics. ISBN 978-0-12-411533-0.
- Isaacson, Walter (2004). Benjamin Franklin: An American Life. ISBN 978-0-7432-5807-4.
- Jackson, Joe (2005). World on Fire. ISBN 978-0-670-03434-5.
- LeMay, J. A. Leo (1987). Benjamin Franklin: Writings. ISBN 978-0-940450-29-5.
- Lemay, J. A. Leo (2009). The Life of Benjamin Franklin, Volume 3: Soldier, Scientist, and Politician, 1748–1757. ISBN 978-0-8122-4121-1.
- Lynn, Barry C. (2009). Cornered: The New Monopoly Capitalism and the Economics of Destruction. ISBN 978-0-470-55703-7.
- Maclean, John (1877). History of the College of New Jersey: From Its Origin in 1746 to the Commencement of 1854. Lippincott.
- Matthews, Robert (June 1, 2003). "Benjamin Franklin 'faked kite experiment'". The Telegraph. Retrieved February 6, 2017.
- McGrath, Kimberley A. (2001). The Gale Encyclopedia of Science: Catastrophism-Eukaryotae. ISBN 978-0-7876-4372-0.
- McNichol, Tom (2006). AC/DC: The Savage Tale of the First Standards War. ISBN 978-1-118-04702-6.
- Morgan, Edmund Sears (2003). Benjamin Franklin. ISBN 978-0-300-10162-1.
- Malmivuo, Jaakko; Plonsey, Robert (1995). Bioelectromagnetism: Principles and Applications of Bioelectric and Biomagnetic Fields. ISBN 978-0-19-505823-9.
- Pasles, Paul C. (2008). Benjamin Franklin's Numbers: An Unsung Mathematical Odyssey. ISBN 978-0-691-12956-3.
- Pyenson, Lewis; Gauvin, Jean-François (2002). Art of Teaching Physics. ISBN 978-2-89448-320-6.
- Schafer, Larry E. (1992). Taking Charge: An Introduction to Electricity. ISBN 978-0-87355-110-6.
- Schiffer, Michael B. (2003). Draw the Lightning Down. ISBN 0-520-23802-8.
- Schiffer, Michael B. (2004). "Bolt of Fate: Benjamin Franklin and His Electric Kite Hoax (review)". S2CID 109344397.
- Schofield, Robert E. (1997). Enlightenment of Joseph Priestley. ISBN 0-271-04083-1.
- Secor, Robert (1975). Pennsylvania: 1776. ISBN 978-0-271-01217-9.
- Talbott, Page (2005). Search of a Better World. ISBN 978-1-4379-6732-6.
- Tucker, Tom (2005). Bolt of Fate. ISBN 978-0-7867-3942-4.
- Waldstreicher, David (2005). Runaway America. ISBN 978-0-8090-8315-2.
External links
- Benjamin Franklin's electrical apparatus (electrostatic machine) at Smithsonian National Museum of American History
- The Amazing Adventures of Ben Franklin – Scientist & Inventor / Opposites Attract with picture of glass globe on top
- Franklin's Electrostatic Generator information and picture from University of Maryland Electrical and Computer Engineering Dept. Archived 2016-12-06 at the Wayback Machine