In the mid-18th century, American polymath Benjamin Franklin conducted a famous experiment that demonstrated the electrical nature of lightning. By flying a kite with a metal key attached to the kite string during a thunderstorm, Franklin was able to collect electric charge from the atmosphere. This groundbreaking experiment laid the foundation for the invention of the lightning rod and greatly contributed to humanity's understanding of electricity. But how exactly did Franklin's simple kite and key lead to the development of the complex electrical wiring systems we rely on today?

Franklin's Kite Experiment

Benjamin Franklin is best known as one of America's Founding Fathers, but he was also a prolific inventor and scientist. As early as 1747, he began conducting experiments with static electricity using glass tubes and other apparatus he devised. By 1752, Franklin had theorized that lightning was an electrical phenomenon, despite the commonly held belief that it was supernatural in nature.

To test his hypothesis, Franklin proposed a daring experiment: he would construct a kite with a metal tip and fly it during a thunderstorm, allowing the kite to be struck by the high voltage in the atmosphere. Franklin attached a metal key to the kite string to collect the electric charge. He then tied a Leyden jar to the string, which would store and isolate the captured electricity. During the experiment, Franklin placed his hand near the key and was able to draw sparks of static electricity from it, proving that lighting was indeed electrical.

This dangerous feat demonstrated that lightning could be harnessed using metal rods and conductors on the ground. Within months, Franklin had invented the lightning rod to safely direct strikes away from buildings and ships. The Paris Academy of Sciences soon repeated Franklin's experiment using a long iron rod in place of a kite and key. These pioneering findings revealed the principles of electrical grounding and conductivity and overturned ancient misconceptions about lightning.

Contributions to Electrical Theory

Franklin's recognition that electricity could be drawn downwards from the sky was revolutionary for 18th century science. At the time, the nature of electricity was poorly understood. But Franklin's kite experiment suggested that the atmosphere has an abundance of electric charge, which could be collected through tall metal rods.

Based on his observations, Franklin developed an early one-fluid theory of electricity. He posited that electricity was a type of invisible electrical fluid that existed in all matter. Objects could be charged positively or negatively depending on whether they had an excess or shortage of this fluid. Although later rendered obsolete by modern physics, Franklin's electrical fluid theory was an important step towards unifying various electrical phenomena.

Franklin also coined much of the terminology used in modern electrical science, including terms like battery, conductor, condenser, charge, discharge, electric shock, and electrician. He differentiated between electrical conductors, like metals, and insulators, like glass. Franklin saw electricity as a powerful natural force that could be studied scientifically and applied for humanity's benefit, a paradigm shift for the era.

Franklin's Influence on Electrical Engineering

The insights from Franklin's kite experiment inspired many practical applications that formed the foundations of modern electrical engineering. For example:

Without Franklin's empirical studies on electricity, these technologies may not have emerged until much later. The Franklin stove, bifocal glasses, the postal service, and the armonica were just a few of his other innovations that contributed to early engineering advancements.

Harnessing Electricity in the 19th and 20th Centuries

In the century after Franklin, rapid progress was made in electrical technology, building upon Franklin's discoveries:

As electrical generators and motors became more efficient in the Industrial Revolution, cities began laying copper wiring to interconnect buildings into municipal electrical grids. Early transmission lines carried direct current over short distances. But the alternating current transformer enabled large-scale transmission over hundreds of miles.

Thomas Edison pioneered direct current distribution networks that illuminated cities and electrified American homes. Meanwhile, Nikola Tesla championed alternating current as the basis for nationwide transmission, having epic battles with Edison. By the early 20th century, AC power grids connected regions together and made electricity ubiquitous.

Franklin could scarcely imagine dense electrical grids powering entire cities. But the practical electrical engineering of modern civilization owes a debt to Franklin's fundamental theories about electricity in nature. His simple kite experiment unleashed innovations across centuries.


From humble beginnings using just a kite, key, and jar, Benjamin Franklin uncovered the hidden electrical nature of lightning and pioneered theories about electricity. His empirical approach overturned misconceptions and enabled him to invent the lightning rod, establish electrical terminology, and envision novel applications. Franklin's findings directly contributed to the development of batteries, generators, motors, and electrical transmission, the building blocks of modern power grids. While the complex wiring inside our walls would astonish Franklin, it is built on principles he revealed with his revolutionary kite-flying experiment. The next time the lights turn on, we have Benjamin Franklin to thank for fundamentally electrifying our world.