How Benjamin Franklin's Key and Kite Experiment Jumpstarted the Electrical Age

Benjamin Franklin's Interest in Electricity

Benjamin Franklin had long been interested in electricity. As a printer and publisher in Philadelphia, I became fascinated by accounts of electrical experiments taking place in Europe. In particular, I was intrigued by the Leyden jar, an early form of capacitor invented by Pieter van Musschenbroek that could store static electricity.

Eager to learn more, I began my own investigations into electricity in the 1740s. At the time, the nature of electricity was not well understood. Most saw it as a mysterious force that could be generated by friction. There were many unanswered questions: What was the source of this force? How did it behave? Could it be controlled or harnessed? I aimed to find out.

The Concept of Positive and Negative Charge

One key insight I had was that there were two types of electrical charge, which I called positive and negative. I noticed that like charges repelled each other, while opposite charges attracted. This led me to theorize that electrical phenomena were caused by an imbalance between these two types of charge.

To test this, I performed experiments, such as creating static charge using glass tubes. When I rubbed the glass with cloth, it gained a certain type of charge. I could then transfer this charge to other objects, like rings of metal. My experiments showed that charged objects would either repel or attract each other, depending on their charges.

This concept of positive and negative electricity was groundbreaking. It marked a major step toward understanding the nature of electricity.

The Lightning Rod

As I continued my investigations, I became increasingly interested in lightning. I wondered if lightning was simply a giant electric spark, caused by imbalanced positive and negative charge within clouds. This raised the question - could lightning be controlled or redirected?

To find out, I devised an experiment with a metal rod attached to a high structure. I hypothesized that if a building's rod was hit by lightning, the electrical charge would travel down the rod and disperse into the ground below. This would protect the building from fire or damage.

In 1752, I worked with others to set up a 40-foot rod atop a church steeple in Philadelphia. When the rod was struck by lightning, my theory proved correct! The church was unharmed. This success demonstrated that lightning rods could protect buildings by safely earthing electric charge.

The Kite and Key Experiment

My most famous electrical experiment took place in 1752. I wanted to gather evidence that lightning was indeed electrical in nature. To do this, I decided to collect charge from a storm cloud by flying a kite with a pointed wire attached to its top.

As the kite flew upwards into the stormy sky, I fastened a metal key to the kite string. My hypothesis was that the kite's wire would collect electric charge from the clouds, which would then travel down the wet kite string and accumulate on the key. I could then use the charged key to create sparks, showing that lightning was electrical.

My son William and I went out during a thunderstorm and carried out the experiment. Just as I hypothesized, electrical sparks jumped from the key to my knuckle! This groundbreaking experiment proved that lightning was caused by electricity. It also demonstrated that electricity could be collected from the atmosphere.

The experiment was a major milestone in our understanding of electricity. It captured the public imagination and made me internationally famous as an authority on electricity. My pioneering electrical research, especially the kite experiment, was crucial in transforming electricity from an academic curiosity into a viable technological and commercial enterprise. It quite literally helped jumpstart the electrical age.