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He developed and produced his lightning rod invention from what he learned about static electricity principles from his electrostatic machine.{{sfn|Radmanesh|2005|page=231}}{{sfn|Coulson|1950|page=32}} He figured out then to put a pointed iron rod at roof tops to protect a wooden structure as the electrical discharge from the cloud would hit the pointed iron rod instead and go directly down into the ground harmlessly where the other end of the rod was anchored.{{sfn|Radmanesh|2005|page=231}}{{sfn|Grimnes|2014|page=496}}{{sfn|McNichol|2011|page=21}} Before Franklin's discovery it was thought that lightning and thunder was some form of exploding gases.{{sfn|Baigrie|2007|page=40}}
He developed and produced his lightning rod invention from what he learned about static electricity principles from his electrostatic machine.{{sfn|Radmanesh|2005|page=231}}{{sfn|Coulson|1950|page=32}} He figured out then to put a pointed iron rod at roof tops to protect a wooden structure as the electrical discharge from the cloud would hit the pointed iron rod instead and go directly down into the ground harmlessly where the other end of the rod was anchored.{{sfn|Radmanesh|2005|page=231}}{{sfn|Grimnes|2014|page=496}}{{sfn|McNichol|2011|page=21}} Before Franklin's discovery it was thought that lightning and thunder was some form of exploding gases.{{sfn|Baigrie|2007|page=40}}

Franklin even gave a demonstration in 1750 of his proof that lightning was just a giant static electricity discharge by setting up miniature houses and steeples with removable lightning rods. These had little bits of gun powder in them. When one of these minitures were hit with a strong electric charge from his machine they exploded going into flames. With another miniature he had a lightning rod attached to it that went into the ground. It would hit it also with this same electric charge and nothing happened, as the electric charge went safely into the ground bypassing the miniature house or steeple. There were dollhouses used in lecture demonstrations in 1751 to show this principle. There was an advertisement in the ''Pennsylvania Gazette'' in April of 1751 saying "How to secure houses from being hurt by its destructive violence."{{sfn|Lemay|2014|page=91}}


== Book on electricity ==
== Book on electricity ==
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*{{cite book |last=Labaree|first=Leonard Woods |date=1961|title=The Papers of Benjamin Franklin, Volume 3 |url= http://yalepress.yale.edu/book.asp?isbn=9780300006520|location= |publisher=Yale University Press |page= |isbn=0300006527 |access-date= |ref=harv}}
*{{cite book |last=Labaree|first=Leonard Woods |date=1961|title=The Papers of Benjamin Franklin, Volume 3 |url= http://yalepress.yale.edu/book.asp?isbn=9780300006520|location= |publisher=Yale University Press |page= |isbn=0300006527 |access-date= |ref=harv}}

*{{cite book |last=Lemay |first=J. A. Leo |date=2014 |title=The Life of Benjamin Franklin, Volume 3: Soldier, Scientist, and Politician, 1748-1757 |url= |location= |publisher=University of Pennsylvania Press |page= |isbn=0812291417 |access-date= |ref=harv}}


*{{cite book |last=Lynn|first=Barry C. |date=2009 |title=Cornered: The New Monopoly Capitalism and the Economics of Destruction |url= |location= |publisher=John Wiley & Sons |page= |isbn=0470557036 |access-date= |ref=harv}}
*{{cite book |last=Lynn|first=Barry C. |date=2009 |title=Cornered: The New Monopoly Capitalism and the Economics of Destruction |url= |location= |publisher=John Wiley & Sons |page= |isbn=0470557036 |access-date= |ref=harv}}

Revision as of 22:03, 20 July 2015

Franklin's electrostatic machine

Franklin's electrostatic machine is a high voltage static electricity generating device that was used by Benjamin Franklin for research in the mid-eighteenth century. Experiments from it eventually lead to the invention of the lightning rod and new theories about electricity.

Benjamin Franklin

Main article: Benjamin Franklin § electricity

One problem Benjamin Franklin had in doing electrical experimentation was getting a good supply of electricity. He knew of the concept that if certain objects were rubbed together they would produce a spark of electricity for a second and that was about it. He needed a source of electricity a little longer than this to do experimental research.[1] Peter Collinson, a wealthy businessman from London, donated a Leyden jar rechargeable storage battery to Franklin's Library Company of Philadelphia in 1746. Franklin wrote a letter to him on March 28, 1747, thanking him for the Leyden jar. He pointed out that this battery and the directions of operation that came with it motivated him and several of his colleges to get excited about doing serious electrical experimentation.[2] Franklin advanced the principle of generating a spark of electricity and went about to develop an electrostatic machine to continually generate electrical sparks for a supply of electricity stored by a Leyden jar.[3]

Description of machine

Globe generator of static electricity

The electrostatic machine was designed and built with help by Thomas Hopkinson, Ebenezer Kinnersley and Philip Syng, associates of Franklin in these electrical experiments.[4][5] It supplied sparks to a Leyden jar so Franklin would have a source of electricity on demand. It was Syng that did the actual construction assembly of the electrostatic machine that was made in Philadelphia. The machine consisted of a rotating nine inch glass globe made by Wistarburgh Glassworks of New Jersey and a piece of chamois leather buckskin in the form of a pad. The glass globes were handled with much care and kept in flannel lined cases that were specifically designed around the globe for protection from breaking and soiling the surface. When mounted on an axel the glass globe represented that of a grindstone turning.[6]

Franklin talked about how the Europeans charged the glass globe by rubbing it with manual labor and how tiring it was with the extensive labor required. His machine was far superior to getting a static charge.[6] The globe turned because of a leather belt that was attached to a larger cranked wooden wheel. The globe built up an electric charge since it rubbed against the chamois pad causing an excess of electrons and an electrical charge.[7] A set of connected metal knitting needles then just barely touched the charged globe which caused sparks. The electricity was passed through a metal link wire to the Leyden jar, electrically charging it.[8][9]

Franklin then did electrical experiments with this continual supply of electricity that could be made on demand from static charges that developed on the glass globe when it turned and rubbed against the chamois pad.[3][10] A few revolutions charged a Leyden jar.[6] He started his experiments on electricity in the winter of 1746-1747.[11][8] Franklin referred to this static electricity as electric "fire" and sometimes as electric "fluid" and other times as electric "matter."[12]

Electrical principles

An electrical principle that Franklin proved with his electrostatic machine was that of conservation of charge - that "positive" and "negative" charges come out in even amounts and are always balanced.[13] He was the first to use the terms "positive" and "negative" ("plus" and "minus") as applied to electricity.[14] He devised the theory from this that electricity is a single "fluid" that is in all matter.[15][16] Franklin currents is electrostatic electricity and of his namesake.[17] "Franklinization" is electrotherapy where Franklin applied strong static charges, from powerful Leyden jars that were charged from his electrostatic machine, to treat patients of various illnesses.[18][19]

Franklin's experiments in charging a Leyden jar with his electrostatic machine developed into connecting a bank of Leyden jars in series with one hanging on the tail of the other that could all be charged at once with his electrostatic machine globe.[12] Franklin called these a "battery", a military term used at the time for a group cannons.[20]

Franklin's Leyden "battery" of jars was given in compliance to Franklin's will from Joseph Hopkinson (Thomas Hopkinson's grandson) to the Royal Society on April 1, 1836.[21]

Lightning rod

Main article: Lightning rod
Franklin's sentry-box experiment of iron rod

Franklin in his letters to Collinson suggested an experiment be performed that would prove principles he learned from his electrostatic machine concerning sharp points attracting electricity. A sentry box was to be built big enough to hold a man and an insulated clean dry stand (see bottom of illustration "Franklin's electrostatic machine"). There was to be a bent pointed iron rod going out the door that rose to the sky 20 to 30 feet. A man was to stay inside the box holding the rod with an insulated wax handle.[22] The idea was that if clouds contained electricity then it would be attracted to the rod with a point. The experimented suggested by Franklin was first done at Marly-la-Ville in the spring of 1752. The iron rod attracted sparks of fire from the electrified clouds. This experiment was repeated several times in different places in Europe.[23]

Franklin observed the principle that pointed objects had a better effect of drawing off and throwing off electricity than a blunt object. He then got thinking how this could be applied to practical use and wrote Collinson about it. Franklin went a step further and made a kite that attracted the electrical charge from the clouds. The kite on the top had a pointed wire. Near the bottom of the string flying the kite was a key just atop a Leyden jar. He held the kite string with a silk ribbon for insulation against the electricity of a lightning bolt. His 21 year old son was with him during this experiment for assistance and as a witness. They hid under a roof of a shed for protection from the rain. A lightning bold hit the wire on the kite, traveled down the wet kite string and through the key and sparked the Leyden jar, charging it just like his electrostatic machine did.[24] He proved from this experiment and his electrostatic machine that lightning is a giant electric spark.[22][25][26]

He developed and produced his lightning rod invention from what he learned about static electricity principles from his electrostatic machine.[16][27] He figured out then to put a pointed iron rod at roof tops to protect a wooden structure as the electrical discharge from the cloud would hit the pointed iron rod instead and go directly down into the ground harmlessly where the other end of the rod was anchored.[16][17][28] Before Franklin's discovery it was thought that lightning and thunder was some form of exploding gases.[29]

Franklin even gave a demonstration in 1750 of his proof that lightning was just a giant static electricity discharge by setting up miniature houses and steeples with removable lightning rods. These had little bits of gun powder in them. When one of these minitures were hit with a strong electric charge from his machine they exploded going into flames. With another miniature he had a lightning rod attached to it that went into the ground. It would hit it also with this same electric charge and nothing happened, as the electric charge went safely into the ground bypassing the miniature house or steeple. There were dollhouses used in lecture demonstrations in 1751 to show this principle. There was an advertisement in the Pennsylvania Gazette in April of 1751 saying "How to secure houses from being hurt by its destructive violence."[30]

Book on electricity

Franklin sent back many letters to his friend Collinson in London on his electrical experiments of using his electrostatic machine and the Leyden jar.[23] He included his theories on the principles on how electricity worked. These letters were eventually assembled and published as a book, Experiments and Observations on Electricity.[23]

References

Citations

  1. ^ "Benjamin Franklin". Complete Dictionary of Scientific Biography. 2008. Retrieved July 16, 2015.
  2. ^ "From Benjamin Franklin to Peter Collinson, 28 March 1747". Founders Online. National Historical Publications and Records Commission. Retrieved July 15, 2015.
  3. ^ a b Fleming 2014, p. 49.
  4. ^ Spencer 2015, p. 1014.
  5. ^ Cohen 1956, p. 434.
  6. ^ a b c Cohen 1956, p. 440.
  7. ^ Cohen 1956, p. 441.
  8. ^ a b Feldman 2014, p. 36.
  9. ^ Heilbron 2003, p. 459.
  10. ^ Van Vleet 2007, p. 98.
  11. ^ Grimnes 2014, p. 495.
  12. ^ a b Cohen 1956, p. 460.
  13. ^ Labaree 1961, p. 142.
  14. ^ McNichol 2011, p. 16.
  15. ^ Warkentin-Glenn 2006, p. 86.
  16. ^ a b c Radmanesh 2005, p. 231.
  17. ^ a b Grimnes 2014, p. 496.
  18. ^ Schiffer 2003, pp. 136, 137.
  19. ^ "Electro-therapeutics". The Encyclopedia Americana: A universal reference library comprising the arts and sciences. Scientific American Compiling Department. 1905.
  20. ^ Lynn 2009, p. 136.
  21. ^ Cohen 1956, p. 454B.
  22. ^ a b McNichol 2011, p. 18.
  23. ^ a b c McNichol 2011, p. 19.
  24. ^ McNichol 2011, p. 20.
  25. ^ Chisholm, Hugh (1910). "Electricity". The Encyclopædia Britannica. Vol. 9 (12 ed.). Encyclopædia Britannica Company. p. 181.
  26. ^ Cajori 1917, pp. 121–134.
  27. ^ Coulson 1950, p. 32.
  28. ^ McNichol 2011, p. 21.
  29. ^ Baigrie 2007, p. 40.
  30. ^ Lemay 2014, p. 91.

Sources

  • Baigrie, Brian Scott (2007). Electricity and Magnetism: A Historical Perspective. Greenwood Publishing Group. ISBN 0313333580. {{cite book}}: Invalid |ref=harv (help)
  • Cajori, Florian (1917). A History of Physics in Its Elementary Branches: Including the Evolution of Physical Laboratories. Macmillan. {{cite book}}: Invalid |ref=harv (help)
  • 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. {{cite book}}: Invalid |ref=harv (help)
  • 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. {{cite book}}: Invalid |ref=harv (help)
  • Feldman, Eve B (2014). Benjamin Franklin: Scientist and Inventor: Scientist and Inventor. StarWalk Kids Media. {{cite book}}: Invalid |ref=harv (help)
  • Fleming, Candace (2014). Ben Franklin's Almanac: Being a True Account of the Good Gentleman's Life. Simon and Schuster. ISBN 1481417991. {{cite book}}: Invalid |ref=harv (help)
  • Grimnes, Sverre (2014). Bioimpedance and Bioelectricity Basics. Academic Press. ISBN 0124115330. {{cite book}}: Invalid |ref=harv (help)
  • Heilbron, John L. (2003). The Oxford Companion to the History of Modern Science. Oxford University Press. ISBN 0199743762. {{cite book}}: Invalid |ref=harv (help)
  • Lemay, J. A. Leo (2014). The Life of Benjamin Franklin, Volume 3: Soldier, Scientist, and Politician, 1748-1757. University of Pennsylvania Press. ISBN 0812291417. {{cite book}}: Invalid |ref=harv (help)
  • Lynn, Barry C. (2009). Cornered: The New Monopoly Capitalism and the Economics of Destruction. John Wiley & Sons. ISBN 0470557036. {{cite book}}: Invalid |ref=harv (help)
  • McNichol, Tom (2011). AC/DC: The Savage Tale of the First Standards War. John Wiley & Sons. ISBN 1118047028. {{cite book}}: Invalid |ref=harv (help)
  • Radmanesh, Matthew M. (2005). The Gateway to Understanding: Electrons to Waves and Beyond. AuthorHouse. ISBN 1418487406. By charging a Leyden jar during a thunderstorm, Franklin and his son demonstrated that lightning and electricity (as produced by an electrostatic machine) are identical. He put his knowledge to work and invented lightning rods on roof tops to dissipate the thunder-cloud charge gradually and harmlessly to ground. {{cite book}}: Invalid |ref=harv (help)
  • Schiffer, Michael B. (2003). Draw the Lightning Down: Benjamin Franklin and Electrical Technology in the Age of Enlightenment. University of California Press. ISBN 0520238028. {{cite book}}: Invalid |ref=harv (help)
  • Spencer, Mark G. (2015). The Bloomsbury Encyclopedia of the American Enlightenment. Bloomsbury Publishing. ISBN 1474249841. {{cite book}}: Invalid |ref=harv (help)
  • Van Vleet, Carmella (2007). Amazing BEN FRANKLIN Inventions: You Can Build Yourself. Nomad Press. ISBN 1619301253. {{cite book}}: Invalid |ref=harv (help)
  • Warkentin-Glenn, Denise (2006). Electric Power Industry in Nontechnical Language. PennWell Books. ISBN 1593700679. {{cite book}}: Invalid |ref=harv (help)
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