How Benjamin Franklin's Key and Kite Experiments Ushered in the Electrical Age (And How You Can Still Do Them Today)

Benjamin Franklin and the Discovery of Electricity

Benjamin Franklin is one of the most famous American inventors and statesmen. He had a deep curiosity about the natural world, especially electricity. In the mid-18th century, little was known about the nature of electricity and lightning. Some scientists had performed experiments showing that electricity could be collected in jars, but its relationship to lightning was not understood.

Franklin hypothesized that lightning was simply electricity occurring on a massive scale. To test this idea, he designed his famous kite and key experiment in 1752. I crafted a kite out of silk, with a metal spike on the top. The kite string was also metal but insulated, except at the bottom where it attached to a key. During a thunderstorm, I went out into a field and flew the kite, allowing it to collect charge from the storm clouds. When I brought my knuckle close to the key, I received a strong electrical spark, showing that the kite had conducted electricity from the lightning!

This groundbreaking experiment proved that lightning is indeed electrical. It paved the way for Benjamin Franklin's later inventions, including the lightning rod. It also helped spur a wave of electrical research and technologies that truly ushered in the "electrical age."

How Franklin's Kite Experiment Worked

To understand how Ben Franklin's experiment worked, we need to understand a few basics about electricity. When certain materials rub against each other, they can exchange electrical charge. This generates positive and negative charges, or static electricity. In a thunderstorm, the negative charges at the bottom of the cloud induce positive charges on the ground and on objects like Franklin's kite. His kite acted as a conductor between the ground and the storm cloud, allowing electricity to flow down the kite string.

The metal key attached to the kite string gave Franklin a way to safely access this electrical charge. By bringing his knuckle close to the key, a spark jumped the small gap between them. This showed that the kite was indeed electrified by the lightning storm. Without taking this important precaution, touching the string could have given Franklin a dangerous or deadly shock!

How You Can Replicate the Kite Experiment Today

Although lightning is now well understood, many people wish they could reproduce Franklin's iconic electrical experiment. This is typically not advisable due to the high risks involved. However, with proper safety precautions, it is possible to replicate the kite experiment on a small scale.

Here is one method:

This setup allows you to gather electric charge from the atmosphere, similar to Franklin's experiment. For classroom demos, an electroscope can detect the charge instead of using a piezoelectric crystal. Always emphasize electrical safety! While not as dramatic as Franklin's original, this replicates his ingenuity on a smaller scale.

Franklin's Legacy: Advancing Science and Invention

Benjamin Franklin pioneered electrical technologies like the lightning rod, battery, and bifocals based on his kite experiment findings. It revealed a deep connection between electricity and lightning, launching the field of electrical studies. Franklin's insight helped shift science from speculation into quantifiable experiments.

Today, we live in the advanced electrical age Franklin helped usher in. Next time you flip on a light switch or charge your phone, you have Ben Franklin and his simple kite experiment to thank! Replicating it yourself is an exciting way to follow in the inventor's footsteps.