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This year marks the 300th anniversary of Benjamin Franklin’s birth. Franklin, the tenth son of a soap maker, received very little formal schooling growing up. He was later apprenticed to his older brother, a printer, which gave him the opportunity to read books. Franklin was always curious and eager to learn. This curiosity drove his experiments with electricity, which made him famous as a scientist.
In December 1750, Franklin learned one lesson the hard way, when he shocked himself while trying to electrocute a holiday turkey. Franklin believed electrocuting the turkey made it uncommonly tender.
When he began his electrical experiments in about 1745, Franklin had already retired from his printing business, which was good, because he soon became so absorbed in the experiments he had little time for anything else. “I never was before engaged in any study that so totally engrossed my attention and my time, as this has lately done,” Franklin wrote to his English friend Peter Collinson in a letter thanking him for the gift of a Leyden jar with directions for charging it.
To most of Franklin’s contemporaries, electricity was mainly useful for parlor games. Few people at the time anticipated any practical use for electricity. Franklin was among the first to study the phenomenon scientifically.
To be sure, Franklin had a great sense of humor and clearly enjoyed the parlor tricks, and he liked having an audience for his electrical amusements. For instance, in the early summer of 1749, somewhat disappointed at not yet having produced anything of great use to mankind with electricity, Franklin hosted an elaborate electrical barbecue. He killed a turkey by electrical shock, then roasted it using the electrical jack, an electric device he invented that would rotate the turkey as it roasted before a fire, which was kindled by an electrified bottle. Guests drank from electrified glasses that gave them a small shock as they sipped their wine, and were entertained as sparks were sent across the river. Franklin also devised a game called “treason,” which involved an electrified portrait of the king, with a removable gilt crown. The picture was rigged so that anyone who tried to remove the crown while holding the gilt edge of the picture would be shocked.
Yet Franklin was interested in electricity for more than entertainment. He studied electricity seriously, and made many meticulous experiments, which he recorded in numerous letters to his friends. His investigations used simple apparatus that included Leyden jars, glass rods, silk, cork, various metals, etc. Franklin not only carried out many electrical experiments, he attempted to explain what he was observing. Based on these observations, Franklin determined that the “electrical fire,” as he called it, was a conserved quantity. He introduced the notion that positively charged objects contained an excess of electrical fire, while negatively charged objects had a deficit. He investigated which objects could be made to attract or repel each other. He determined that sharp points could “draw off” or “throw off” electrical fire, and later applied this knowledge to the design of lightning rods. He is most famous for his kite experiment showing that lightning is an electrical phenomenon.
But not all of his experiments went well. In a letter dated 25 December 1750, Franklin describes his attempt to electrocute a turkey, which didn’t work out as he had intended, “I have lately made an experiment in electricity that I desire never to repeat. Two nights ago, being about to kill a turkey by the shock from two large glass jars, containing as much electrical fire as forty common phials, I inadvertently took the whole through my own arms and body, by receiving the fire from the united top wires with one hand, while the other held a chain connected with the outsides of both jars.”
The audience for this accident reported that they had seen a great flash and heard a loud crack, but Franklin didn’t notice this, having been shocked senseless. He did record that “the first thing I took notice of was a violent, quick shaking of my body, which gradually remitting, my sense as gradually returned.” Franklin felt some numbness for a short while afterwards, and experienced some soreness for a few days, but otherwise, he suffered only from embarrassment at his mistake. He made an effort to warn others against making a similar mistake when conducting such dangerous experiments.
Franklin wrote about this event and his many other experiments in his letters, and in 1751 published a book, Experiments and Observations on Electricity, which became very popular. He continued his scientific work for which he was by then well known, and in 1752 conducted the famous kite experiment mentioned above. In addition to his electrical research, Franklin investigated heat conduction, weather patterns, and the Gulf Stream, and invented many practical devices such as the Franklin stove, bifocals, daylight savings time, and the lightning rod.
Further reading: Benjamin Franklin and Electrostatics
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