Electricity Discoveries by Benjamin Franklin, How to Make a Leyden Jar Experiment

Franklin Flies a Kite

As it turns out, Benjamin Franklin did not discover electricity. What’s more, the kite he famously flew in 1752 while conducting an experiment was not struck by lightning. If it had been, Franklin would be remembered as a colonial publisher and assemblyman killed by his own curiosity.

Before Ben

Blessed with one of the keenest minds in history, Benjamin Franklin was a scientific genius who made groundbreaking discoveries in the basic nature and properties of electricity. Electrical science, however, dates to 1600, when dr. William Gilbert, physician to Queen Elizabeth, published A Treatise about his research on electricity and magnetism. European inventors who later expanded on Gilbert’s knowledge included Otto von Guericke of Germany, Charles Francois du Fay of France, and Steven Gray of England.

The Science of Electricity

Franklin became fascinated with electricity after seeing a demonstration by an itinerant Showman, a doctor named Archibald Spencer in Boston in 1743. Two years later he bought a Leyden jar, a contraption invented by a Dutch scientist that used a glass container wrapped in foil to create a crude battery.

Other researchers had demonstrated the properties of the device, and Franklin set about to increase its capacity to generate electricity while testing his own scientific hypotheses. Among the principles he established was the conservation of charge, one of the most important laws of physics. In a paper published in 1750, he announced the discovery of the induced charge and broadly outlined the existence of the electron. His experiments led him to coin many of the terms currently used in the science of electricity, such as battery, conductor, condenser, charge, discharge, uncharged, negative, minus, plus, electric shock, and electrician.

As Franklin came to understand the nature of electricity, he began to theorize about the electrical nature of lightning. In 1751 he outlined in a British scientific journal his idea for an experiment that involved placing a long metal rod on a high tower or steeple to draw an electric charge from passing thunderclouds, which would throw off visible electric sparks. A year later, Georges-Louis Leclerc successfully conducted such an experiment.

The Kite Runner

Franklin had not heard of Leclerc’s success when he undertook his own experiment in June 1752. Instead of a church Spire, he affixed his kite to a sharp pointed wire to the end of his kite string he tied a key, and to the key a ribbon made of silk, for insulation. Well flying his kite on a cloudy day as a thunderstorm approached, Franklin noticed that loose threads on the kite string stood erect, as if they had been suspended from a common conductor. The key sparked when he touched it, showing it was charged with electricity. Had the kite actually been struck by lightning, Franklin would likely have been killed, as was Professor George Wilhelm Richmann of St Petersburg, Russia, when he attempted the same experiment a few months later.

The Lightning Rod

Although Franklin did not discover electricity, he did uncover many of its fundamental principles and proved that lightning is, in fact, electricity. He used his knowledge to create the lightning rod, and invention that today protects land structures and ships at sea. He never patented the lightning rod, but instead generously promoted it as a boon to humankind. In 21st century classrooms, the lightning rod is still cited as a classic example of the way fundamental science can produce practical inventions.