Benjamin Franklin was one of America's founding fathers and a prolific inventor. His most famous invention was the lightning rod, which protected buildings from lightning strikes. But before inventing the lightning rod, Franklin had to prove that lightning was actually electricity. That's why he conducted his famous kite and key experiment in 1752.
Why Did Benjamin Franklin Conduct the Kite Experiment?
In the 18th century, scientists were debating whether lightning was the same force as the electricity that could be produced in laboratories. Franklin hypothesized that lightning was indeed electrical. But at that time, there was no easy way to collect enough electricity to study it in detail. As Franklin knew, lightning struck from clouds down to the ground. So he decided to use a kite and a key to draw lightning down to him for experimentation.
Some of Franklin's specific goals for his kite experiment were:
-
Prove that lighting is electricity. Up to that point, this relationship was theorized but not shown empirically.
-
Gather electricity from lightning. This would allow him to study electricity in more detail.
-
Study if electricity could be conducted over wire. This could lead to new discoveries and inventions.
-
Protect buildings from lightning. Franklin theorized that if lightning was electricity, it could be controlled and diverted with metal rods.
How Did Franklin's Kite Experiment Work?
On a stormy day in June 1752, Franklin and his son went out into a field to fly a kite with a pointed wire attached to its upright stick. At the end of the kite string, Franklin attached a metal key. He stood under a shelter to avoid the rain and lightning while his son stayed in the field flying the kite.
Here is a step-by-step account of how the experiment worked:
-
As the storm picked up strength, the kite flew higher and higher. The higher it went, the more likely it was to get struck by lightning as it drew closer to the storm clouds.
-
When lightning struck, electricity traveled down the wet kite string and into the key.
-
Franklin touched the key with his knuckle and received an electric shock, proving lightning was electrical.
-
He was able to capture enough electricity from the key to charge a Leyden jar (an early form of battery). This allowed him to study electricity in more detail after the experiment.
-
Franklin noted that the electricity did not shock his son who was holding the string, showing it could travel along metal wire safely.
The Aftermath and Impact of the Kite Experiment
Franklin's kite experiment provided concrete evidence that lightning was electricity. Although others had theorized this relationship, Franklin was the first to empirically prove the electrical nature of lightning. After his experiment, the theory became widely accepted around the world.
By showing that lightning could be conducted by metal wires, Franklin paved the way for his invention of the lightning rod. Lightning rods protect buildings by conducting lightning's electricity safely into the ground. By 1761, lightning rods were being widely installed, saving many structures from fires.
The knowledge gained from Franklin's experiment fueled new research into electricity. Franklin himself continued studying electricity and invented new tools like the lightning bell to alert of impending lightning strikes. Franklin's work helped establish electricity as a subject for scientific inquiry and kicked off more electrical discoveries during the Enlightenment and Industrial Revolution eras.
Today, Franklin is remembered as one of the fathers of electricity, honored for this pioneering kite experiment and for promoting a greater understanding of electrical forces. His simple but ingenious kite test brought an electrical revolution and changed the future development of electrical technology.