June 23, 2014

Lightning, Electricity and Ben Franklin

By Brandon Marie Miller

[Create Charged Cereal!]

With electricity all the rage, Benjamin Franklin wrote an English friend in 1747, "I never was before engaged in any study that so totally engrossed my attention...." Like others, Franklin attended "electrical parties" and performances where men entertained guests with shooting sparks and objects moved with static electricity. A Frenchman even entertained King Louis XV by sending a shock wave through180 soldiers holding hands-- the shock made the men jump in the air delighting spectators.

Franklin collected electrical equipment, including a Leyden jar, a simple battery made from a glass jar holding water and iron filings and lined with metal foil. Franklin used electricity to ring bells, set an "electrical spider" in motion and make sparks light up a portrait of the king. Christmas, 1750, he nearly electrocuted himself when he invited friends to dine on turkeys he'd kill using electricity stored in Leyden jars. Franklin described his near fatal accident: "a universal blow throughout my whole body from head to foot, which seemed within as well as without."

But he wasn't only interested in electricity as entertainment. Franklin devised a series of experiments. He discovered  electricity was not caused by friction, but instead was collected and moved by friction. Franklin determined that electricity was a single "fluid" that had positive or negative charges that occurred in equal amounts. He recognized that "the electric matter consists of particles" so small they passed through matter. He created new English words for the study of electricity: conductor, charge, discharge, electrify and others. He listed 12 characteristics electricity shared with lightning.  Like others, Franklin suspected lightning and electricity where the same thing, but no one had proved this.

A London friend published Franklin's findings in April 1751 as Experiments and Observations on Electricity, Made at Philadelphia in America [above]. The book zipped through multiple printings and translations. Europe went crazy verifying Franklin's experiments. The fact that an uneducated American had written the book made Franklin's work all the more remarkable to Europeans.
The kite experiment with his son William. Courtesy: Charles Mills Murals, Benjamin Franklin Institute of Technology.

Franklin also proposed a detailed experiment, called the "sentry box," to test whether or not lightning was electricity. A Frenchman named d'Alibard conducted the test in May 1572 proving Franklin's predictions correct. Franklin did not know this when he conducted another lightning experiment in June 1752--flying a kite with an attached key into a thunderstorm. A year later he became the first scientist to challenge the idea that lightning struck only from a thundercloud down to the earth. Franklin realized that lightning also sprang from the earth (the positive charge) as the atmosphere tried to balance it electrical equilibrium.

Franklin's breakthrough work with electricity earned him honors and recognition. But he always hoped a practical good might come from his experiments. His work in electricity led to his invention of the lightening rod which safely carried dangerous strikes away from buildings and ships.

Now, try your own experiment in static electricity with a balloon and a piece of cereal.

No comments:

Post a Comment