Benjamin Franklin and Discovery of Electricity
Sound of Thunder (59k)
Have you ever watched lightning during a storm? Have you ever wondered about its power? Have you ever wanted to know more about it? Ben Franklin did. Actually, Ben's interest in electricity was not just limited to lightning. He received an electricity tube from his friend Peter Collinson and began to play around with it, performing experiments. However, it is Ben's interest in lightning that we best remember.
Ben suspected that lightning was an electrical current in nature, and he wanted to see if he was right. One way to test his idea would be to see if the lightning would pass through metal. He decided to use a metal key and looked around for a way to get the key up near the lightning. As you probably already know, he used a child's toy, a kite, to prove that lightning is really a stream of electrified air, known today as plasma. His famous stormy kite flight in June of 1752 led him to develop many of the terms that we still use today when we talk about electricity: battery, conductor, condenser, charge, discharge, uncharged, negative, minus, plus, electric shock, and electrician.
Ben understood that lightning was very powerful, and he also knew that it was dangerous. That's why he also figured out a way to protect people, buildings, and ships from it, the lightning rod.
Have you ever heard of Ben's lightning bells? Ben was always looking for new ideas about electricity, since it was one of his favorite pastimes.
Although electricity was just a hobby for Ben Franklin, he made many important contributions. Later scientists, like Michael Faraday and Thomas A. Edison, continued to study electricity using many of Ben's ideas. Even today, scientists are still studying electricity and learning more about it. They've learned that all citizens need to practice good safety habits, since electricity can be very dangerous. Ben Franklin would be amazed at how important his stormy kite flight really was!
Benjamin Franklin Discovers Electricity
Ben Franklin's Lightning Bells
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This artist's rendering is based upon the text below. The drawing represents just one possible interpretation. No known images exist of the real Franklin bells.
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This rendering, by Steve Nazigian, offers another interpretation. Select the image to visit his website and learn more about his theory.
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Ben also developed another device to help him understand electricity. Called "lightning bells," the bells would jingle when lightning was in the air. Following are two descriptions.
In September 1752, I erected an Iron Rod to draw the Lightning down into my House, in order to make some Experiments on it, with two Bells to give Notice when the Rod should be electrified. A contrivance obvious to every Electrician.
I found the Bells rang sometimes when there was no Lightning or Thunder, but only a dark Cloud over the Rod; that sometimes after a Flash of Lightning they would suddenly stop; and at other times, when they had not rang before, they would, after a Flash, suddenly begin to ring; that the Electricity was sometimes very faint, so that when a small Spark was obtained, another could not be got for sometime after; at other times the Sparks would follow extremely quick, and once I had a continual Stream from Bell to Bell, the size of a Crow-Quill. Even during the same Gust there were considerable variations.
Excerpted from: The Papers of Benjamin Franklin. Edited by Leonard W. Labaree. New Haven: Yale University Press, 1962. Vol. 5, p. 69, letter from Benjamin Franklin to Peter Collinson dated September 1753.
What quantity of lightning a high, pointed rod, well communicating with the earth, may be expected to discharge from the clouds silently in a short time, is yet unknown; but I reason from a particular fact to think it may at some times be very great. In Philadelphia I had such a rod fixed to the top of my chimney, and extending about nine feet above it. From the foot of this rod, a wire (the thickness of a goose-quill) came through a covered glass tube in the roof, and down through the well of the staircase; the lower end connected with the iron spear of a pump. On the staircase opposite too my chamber door, the wire was divided; the ends separated about six inches, a little bell on each end; and between the bells a little brass ball, suspended by a silk thread, to play between and strike the bells when clouds passed with electricity in them. After having frequently drawn sparks and charged bottles from the bell of the upper wire, I was one night awaked by loud cracks on the staircase. Starting up and opening the door, I perceived that the brass ball, instead of vibrating as usual between the bells, was repelled and kept at a distance from both; while the fire passed, sometimes in very large, quick cracks from bell to bell, and sometimes in a continued, dense, white stream, seemingly as large as my finger, whereby the whole staircase was inlightened (sic) as with sunshine, so that one might see to pick up a pin. And from the apparent quantity thus discharged, I cannot but conceive that a number of such conductors must considerably lessen that of any approaching cloud, before it comes so near as to deliver its contents in a general stroke; an effect not to be expected from bars unpointed, if the above experiment with the blunt end of the wire is deemed pertinent to the case.
The Writings of Benjamin Franklin. Edited by Albert Henry Smyth. New York: The Macmillan Company, 1906. Vol. 5, pp. 421-422, "Experiments, observations, and facts tending to support the opinion of the utility of long, pointed rods, for securing buildings from damage by strokes of lightning," by Benjamin Franklin. Read at the Committee appointed to consider the erecting of conductors to secure the [powder] magazines at Purfleet, August 27th, 1772. |
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