Introduction
Benjamin Franklin is one of the most well-known American founding fathers and polymaths. He made major contributions in science, politics, writing, printing, diplomacy and more. One of his most famous scientific contributions was his experiment with electricity using a kite and a key. This simple experiment demonstrated a connection between lightning and electricity and helped jumpstart a new electric age.
Benjamin Franklin's Interest in Electricity
Franklin had long been interested in electricity. In the 1740s, he began conducting experiments with static electricity using glass tubes, spheres and other apparatus. He coined terms like 'battery', 'conductor' and 'charge' that are still used today in electronics.
By the 1750s, Franklin theorized that lightning was an electrical phenomenon. Other scientists like Thomas-François Dalibard and Louis-Guillaume Delor conducted experiments to collect and store electricity from lightning. Franklin wanted to take the next step and actually draw lightning down from a storm cloud.
Preparing the Kite and Key
Franklin prepared for his experiment by making a kite out of a large silk handkerchief attached to a cross stick. At the tip of the kite, he tied a metal key. The kite string was made of common hemp twine except for the bottom end, which was silk. Silk was known to be an electrical insulator so it prevented electricity from conduction down the wet twine.
Flying the Kite in a Storm
On a stormy day in June 1752, Franklin and his son William went out to fly the kite. Franklin chose a local field near his house because he knew it was frequented by lightning storms. As rain fell and wind picked up, Franklin carefully let out more and more wire, raising the kite higher and higher.
As the lightning intensified, Franklin moved under a shelter to stay dry. He then brought his knuckle close to the key and was thrilled when a spark jumped, demonstrating the presence of electricity. Franklin was able to collect electric charge in a Leyden jar from the key, further proving that lightning was indeed electrical.
Aftermath and Significance
After this groundbreaking experiment, Franklin advocated the use of pointed lightning rods on buildings to conduct lightning safely down to the ground. He noted wryly that it was best to use blunt lightning rods on ships so the dangerous lightning would be conducted into the water rather than the vulnerable gunpowder stores below deck.
Franklin's simple kite experiment was a major milestone in the understanding and application of electricity. It showed that lightning was similar to the sparks and currents produced in laboratories. Other scientists like Joseph Priestley were inspired to conduct their own electrical experiments as a result. Franklin's work paved the way for future developments like batteries, generators and electrical motors. The electric age had officially begun!
Later Discoveries about Lightning
Later scientists delved deeper into the properties of lightning and electricity. In the late 18th century, Italian physicist Luigi Galvani showed that electricity could make muscles twitch, establishing the field of bioelectricity. In the 19th century, inventors like Thomas Edison, Nikola Tesla and George Westinghouse developed electrical generators, lights and motors.
Scientists now know that lightning is a massive electrostatic discharge that occurs within clouds or between clouds and the ground. The resulting electrical currents and electromagnetic pulses can reach temperatures of 30,000°C! Modern lightning research uses sophisticated tools like Labs and lasers to study lightning processes. Franklin could scarcely have imagined how far his simple kite experiment would lead.
Conclusion
Benjamin Franklin's groundbreaking kite experiment demonstrated a connection between lightning and electricity. It jumpstarted serious research into electricity and lightning and paved the way for the amazing technological advances of the electric age. Franklin's ingenious experiment will always be remembered as a pivotal moment in scientific history. While using a kite and key today would be extremely dangerous, it was an important early step in harnessing the power of electricity.