experiment with the kite

Benjamin Franklin and the Kite Experiment

We all know the story of Franklin’s famous kite-in-a-thunderstorm experiment. But is it the true story?

On a June afternoon in 1752, the sky began to darken over the city of Philadelphia. As rain began to fall and lightning threatened, most of the city’s citizens surely hurried inside. But not Benjamin Franklin. He decided it was the perfect time to go fly a kite.

Franklin had been waiting for an opportunity like this. He wanted to demonstrate the electrical nature of lightning, and to do so, he needed a thunderstorm.

He had his materials at the ready: a simple kite made with a large silk handkerchief, a hemp string, and a silk string. He also had a house key, a Leyden jar (a device that could store an electrical charge for later use), and a sharp length of wire. His son William assisted him.

Franklin had originally planned to conduct the experiment atop a Philadelphia church spire, according to his contemporary, British scientist Joseph Priestley (who, incidentally, is credited with discovering oxygen), but he changed his plans when he realized he could achieve the same goal by using a kite.

So Franklin and his son “took the opportunity of the first approaching thunder storm to take a walk into a field,” Priestley wrote in his account. “To demonstrate, in the completest manner possible, the sameness of the electric fluid with the matter of lightning, Dr. Franklin, astonishing as it must have appeared, contrived actually to bring lightning from the heavens, by means of an electrical kite, which he raised when a storm of thunder was perceived to be coming on.”

Despite a common misconception, Benjamin Franklin did not discover electricity during this experiment—or at all, for that matter. Electrical forces had been recognized for more than a thousand years, and scientists had worked extensively with static electricity. Franklin’s experiment demonstrated the connection between lightning and electricity.

The Experiment To dispel another myth, Franklin’s kite was not struck by lightning. If it had been, he probably would have been electrocuted, experts say. Instead, the kite picked up the ambient electrical charge from the storm.

Here’s how the experiment worked: Franklin constructed a simple kite and attached a wire to the top of it to act as a lightning rod. To the bottom of the kite he attached a hemp string, and to that he attached a silk string. Why both? The hemp, wetted by the rain, would conduct an electrical charge quickly. The silk string, kept dry as it was held by Franklin in the doorway of a shed, wouldn’t.

The last piece of the puzzle was the metal key. Franklin attached it to the hemp string, and with his son’s help, got the kite aloft. Then they waited. Just as he was beginning to despair, Priestley wrote, Franklin noticed loose threads of the hemp string standing erect, “just as if they had been suspended on a common conductor.”

Franklin moved his finger near the key, and as the negative charges in the metal piece were attracted to the positive charges in his hand, he felt a spark.

“Struck with this promising appearance, he immediately presented his knucle [sic] to the key, and (let the reader judge of the exquisite pleasure he must have felt at that moment) the discovery was complete. He perceived a very evident electric spark,” Priestley wrote.

Using the Leyden jar, Franklin “collected electric fire very copiously,” Priestley recounted. That “electric fire”—or electricity—could then be discharged at a later time.

Franklin’s own description of the event appeared in the Pennsylvania Gazette on October 19, 1752. In it he gave instructions for re-creating the experiment, finishing with:

As soon as any of the Thunder Clouds come over the Kite, the pointed Wire will draw the Electric Fire from them, and the Kite, with all the Twine, will be electrified, and the loose Filaments of the Twine will stand out every Way, and be attracted by an approaching Finger. And when the Rain has wet the Kite and Twine, so that it can conduct the Electric Fire freely, you will find it stream out plentifully from the Key on the Approach of your Knuckle. At this Key the Phial may be charg’d; and from Electric Fire thus obtain’d, Spirits may be kindled, and all the other Electric Experiments be perform’d, which are usually done by the Help of a rubbed Glass Globe or Tube; and thereby the Sameness of the Electric Matter with that of Lightning compleatly demonstrated.

Franklin wasn’t the first to demonstrate the electrical nature of lightning. A month earlier it was successfully done by Thomas-François Dalibard in northern France. And a year after Franklin’s kite experiment, Baltic physicist Georg Wilhelm Richmann attempted a similar trial but was killed when he was struck by ball lightning (a rare weather phenomenon).

After his successful demonstration, Franklin continued his work with electricity, going on to perfect his lightning rod invention. In 1753, he received the prestigious Copley Medal from the Royal Society, in recognition of his “curious experiments and observations on electricity.”

By Nancy Gupton. Published June 12, 2017.

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Benjamin Franklin’s Kite Experiment: What Do We Know?

By: Becky Little

Updated: June 14, 2023 | Original: June 6, 2022

On June 10, 1752, Benjamin Franklin took a kite out during a storm to see if a key attached to the string would draw an electrical charge. Or so the story goes. In fact, historians aren’t quite sure about the date of Franklin’s famous experiment, and some have questioned whether it took place at all.

Even if Franklin’s kite and key experiment did happen, it didn’t play out the way many people think it did. Contrary to popular myths, Franklin didn’t conduct the experiment to prove the existence of electricity. In addition, it’s very unlikely that lightning struck a key while Franklin was flying a kite—because if it had, Franklin probably would have died.

Franklin Didn't Write Much About the Experiment

Everything we know about Franklin’s kite and key experiment comes from two sources . The first is a letter Franklin wrote to his friend Peter Collinson in October 1752 that was published in the The Pennsylvania Gazette and read before the Royal Society. The second is a section of Joseph Priestley’s 1767 book History and Present Status of Electricity , in which Priestley recounted what Franklin had presumably told him about the experiment.

In the letter, Franklin wrote that an “Experiment has succeeded in Philadelphia” using a kite and key, and detailed how one could go about reproducing the experiment. He didn’t specify when the experiment took place or whether he had actually conducted it. Fifteen years later, Priestley provided some more details, writing that 46-year-old Franklin and his 22-year-old son William had conducted the experiment sometime in June 1752.

Scholars of Franklin have speculated that the experiment occurred around June 10, though no one really knows what date it happened on. Some have theorized that it occurred later in 1752, while others have questioned whether it happened at all, or at least acknowledged that there is room for doubt.

“The episode of the kite, so firm and fixed in legend, turns out to be dim and mystifying in fact,” wrote Carl Van Doren in his 1939 Pulitzer Prize-winning biography, Benjamin Franklin . The legendary aspect of the kite and key experiment has led many people believe, incorrectly, that it marked the discovery of electricity.

Ben Franklin Didn't Discover Electricity

Electricity was already a known phenomenon during the mid-18th century. There were, however, debates about the nature of this phenomenon, and Franklin was one of a group of philosophers and scientists who theorized that lightning was a form of electricity.

In March 1750, Franklin wrote a letter to his friend Collinson about his idea for a lightning rod. That July, he published an idea for an experiment using a lightning rod to try and catch an electrical charge in a “leyden jar,” a storage container for electrical charges, thus demonstrating that lightning was a form of electricity.

Franklin’s ideas circulated in Europe, and in May 1752, two French scientists—Thomas Dalibard and M. Delor—separately carried out successful versions of Franklin’s experiment. According to Priestley, Franklin hadn’t yet heard of these successes in June 1752, when he was waiting on the construction of a spire to conduct his own lightning rod experiment.

Apparently, Franklin decided that instead of waiting for the spire, he could test his theory by flying a kite with a key attached to its string when he sensed an approaching thunderstorm. “[D]reading the ridicule which too commonly attends unsuccessful attempts in science, he communicated his intended experiment to noone but his son, who assisted him in raising the kite,” Priestley wrote.

Ben Franklin Didn't Get Struck By Lightning

So what would this experiment have actually looked like? Although many artists have tried to depict it, “most of the pictures and drawings that you see depicting Franklin in this experiment are inaccurate,” says Harold D. Wallace Jr. , a curator in the division of work and industry at the Smithsonian National Museum of American History.

“They show Franklin standing out in the middle of a field,” he says, “whereas most likely he and William were inside some kind of shed or lean-to or something to keep them from getting rained on, in case the rain did start.” (Franklin likely started the experiment after sensing lightning in the air, but before any rain began to fall, says Wallace.)

Franklin’s goal probably wasn’t for the kite and key to get struck by lightning; and indeed, Priestley never claimed that they were struck by lightning. If they had been , Franklin would’ve almost certainly died or at least been seriously injured (in 1753, the German scientist Georg Wilhelm Reichmann died while trying to conduct Franklin’s lightning rod experiment).

What probably happened is that the key picked up some ambient electrical charge from the storm. Priestley wrote that Franklin touched the key and felt the charge, confirming he had caught some electricity from the lightning.

Even if Franklin never actually performed the kite and key experiment, he did come up with the lightning rod idea that others tested. Together, these experiments helped prove that lightning was a form of electricity that people could harness, both to protect tall buildings from damage and to perform more experiments.

“The idea of mitigating natural dangers is such a big game changer,” says Michael Madeja , head of education programs at the American Philosophical Society Library and Museum. “The lightning rod also helped provide a decent source of charge for things like leyden jars or other electrical experiments.”

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Kite Experiment

Flying a kite in a storm was perhaps Benjamin Franklin’s most famous experiment that led to the invention of the lightning rod and the understanding of positive and negative charges. The connection between electricity and lightning was known but not fully understood. By conducting the kite experiment Franklin proved that lighting was an electrical discharge and realized that it can be charged over a conductor into the ground providing a safe alternative path and eliminating the risk of deadly fires.

Erecting iron rods

Iron rod experiment conducted by French scientist Thomas François Dalibard.

Franklin hypothesized that lightning was an electrical discharge. Before he thought of conducting his experiment by flying a kite, he proposed erecting iron rods into storm clouds to attract electricity from them. He also suggested that the tips of the rods should be pointed instead rounded so that they could draw electrical fire out of a cloud silently. Franklin speculated about its usefulness for several years as he was unable to perform his experiment since he thought it had to be  conducted from a higher ground. Philadelphia has a flat geography and at the time there were no tall structures, he was anxiously waiting for the construction of Christ Church that was being built on a steeple to conduct his experiment.

Franklin wrote his proposal for the iron rod experiment in a letter to Peter Collison who was a member of the Royal Society of London. Collison presented Franklin’s hypothesis to the Society who ridiculed and laughed at his idea failing to recognize its significance. A year later when the French translation was published it attracted the interest of French scientists Delor and Dalibard, who separately and successfully conducted Franklin’s experiment calling it the “Philadelphia experiment”.

Franklin was recognized by the Royal Society of London and in scientific circles all over Europe, becoming the most famous American in Europe.

Flying a kite

Franklin kept himself and the end of the string dry to protect himself from being electroshocked.

Franklin had not heard of the success of his experiment in Europe before he conducted the same experiment with a kite. One day in June 1752, it occurred to him that he could test his hypothesis by flying a kite instead of waiting for the church to be built. With the help of his son William he built the body of the kite with two crossed strips of cedar wood and a silk handkerchief instead of paper as it would not tear with wind and rain. They attached a foot long sharp and pointed wire to the top of the kite as a conductor and at the bottom end of the string where it is held they attached a silk ribbon and a metal key. A metal wire connected the key to the Leyden Jar.

Franklin kept dry by retreating into a barn; the end of the string was also kept dry to insulate himself. When the stormed passed over his kite the conductor drew electricity into his kite. The kite was not struck by lightning but the conductor drew negative charges from a charged cloud to the kite, string, metal key and Leyden jar. It appears that he knew enough about grounding to protect himself from being electroshocked. When he moved his hand near the key he received a shock because the negative charge attracted the positive charge in his body.

This is the description of the electric kite experiment in Franklin’s own words from the Pennsylvania Gazette dated October 19, 1752.

As frequent Mention is made in the News Papers from Europe, of the Success of the Philadelphia Experiment for drawing the Electric Fire from Clouds by Means of pointed Rods of Iron erected on high Buildings, &c. it may be agreeable to the Curious to be inform’d, that the same Experiment has succeeded in Philadelphia, tho’ made in a different and more easy Manner, which any one may try, as follows.

Make a small Cross of two light Strips of Cedar, the Arms so long as to reach to the four Corners of a large thin Silk Handkerchief when extended; tie the Corners of the Handkerchief to the Extremities of the Cross, so you have the Body of a Kite; which being properly accommodated with a Tail, Loop and String, will rise in the Air, like those made of Paper; but this being of Silk is fitter to bear the Wet and Wind of a Thunder Gust without tearing. To the Top of the upright Stick of the Cross is to be fixed a very sharp pointed Wire, rising a Foot or more above the Wood. To the End of the Twine, next the Hand, is to be tied a silk Ribbon, and where the Twine and the silk join, a Key may be fastened. This Kite is to be raised when a Thunder Gust appears to be coming on, and the Person who holds the String must stand within a Door, or Window, or under some Cover, so that the Silk Ribbon may not be wet; and Care must be taken that the Twine does not touch the Frame of the Door or Window. As soon as any of the Thunder Clouds come over the Kite, the pointed Wire will draw the Electric Fire from them, and the Kite, with all the Twine, will be electrified, and the loose Filaments of the Twine will stand out every Way, and be attracted by an approaching Finger. And when the Rain has wet the Kite and Twine, so that it can conduct the Electric Fire freely, you will find it stream out plentifully from the Key on the Approach of your Knuckle. At this Key the Phial may be charg’d; and from Electric Fire thus obtain’d, Spirits may be kindled, and all the other Electric Experiments be perform’d, which are usually done by the Help of a rubbed Glass Globe or Tube; and thereby the Sameness of the Electric Matter with that of Lightning compleatly demonstrated.

In 1753 Franklin published an article in Poor Richard’s Almanac describing how to secure houses from lightning.

It has pleased God and his goodness mankind, at length to discover to them the means of securing their habitations and other buildings from mischief by thunder and lightning. The method is this: Provide a simall iron rod but of such a length that one end being three or four deet in the moist ground, the other may be six or eight feet above the highest part of the building. To the upper end of the rod fasten about a foot of brass wire, the size of a common knitting needle, sharpened to a fine point; the rod may be secured to the house by a few small staples. If the house or barn be ling, there may be a rod and point at each end, and a middling wire along the ridge from one to the other. A house thus furnished will not be damaged by lightning, it being attracted by the points and passing thro the metal into the ground without hurting anything.

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Did Benjamin Franklin really discover electricity with a kite and key?

Did the founding father really discover electricity?

On a dark, stormy summer night in 1752, Benjamin Franklin flew a kite with a key attached to the string waiting in anticipation for lightning to strike. The dramatic bolt would harken the discovery of electricity (or as Franklin called it "electrical fire") … or so the story goes.

But is there any truth to this tale? Did Franklin really discover electricity by getting zapped by a lightning bolt during this experiment?

Though most people know Benjamin Franklin — an American founding father, legendary statesman and the face of the U.S. $100 bill — for his political contributions, Franklin was well known in his time as a scientist and an inventor: a true polymath. He was a member of several scientific societies and was a founding member of the American Philosophical Society. As a result, he stayed informed on the most pressing scientific questions that occupied learned people of his time, one of which was the nature of lightning.

As for the kite-and-key experiment, most people are aware of the version in which the metal key acted as a lightning rod, and Franklin subsequently "discovered" electricity when lightning struck his kite. However, several details about this experiment are unknown, including when and where it happened. Some historians even doubt that it took place. 

Related: Did Benjamin Franklin really want the turkey to be the US national bird?

For starters, it's a common myth that Franklin discovered electricity. Electricity had already been discovered and used for centuries before Franklin's experiment. Franklin lived from 1709 to 1790, and during his time, electricity was understood as the interaction between two different fluids , which Franklin later referred to as "plus" and "minus." According to French chemist Charles François de Cisternay du Fay, materials that possessed the same type of fluid would repel, while opposite fluids attracted one another. We now understand that these "fluids" are electrical charges generated by atoms. Atoms are made up of negatively charged electrons orbiting a positively charged nucleus (made up of protons and neutrons).

It was unknown prior to Franklin's experiment whether lightning was electrical in nature, though some scientists, including Franklin, had speculated just that . Page Talbott, author and editor of " Benjamin Franklin: In Search of a Better World " (Yale University Press, 2005) and the former president and CEO of the Historical Society of Pennsylvania in Philadelphia, said that Franklin was particularly interested in this question because lightning strikes had caused disastrous fires in cities and towns where houses were made of wood, which many homes in the U.S. were at the time. "By attaching a key to the string of a kite, thus creating a conductor for the electrical charge , he was demonstrating that a pointed metal object placed at a high point on a building — connected to a conductor that would carry the electricity away from the building and into the ground — could make a huge difference to the long-term safety of the inhabitants," Talbott told Live Science in an email. In other words, by creating a lightning rod, Franklin was helping to protect wooden homes and buildings from being directly struck by lightning.

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Lightning rods are metal rods placed at the top of structures, connected to the ground with a wire. If lightning strikes the building, it will likely strike the electrically conductive rod instead of the building itself and safely run through the wire to the ground.

Here's how the experiment worked; standing in a shed, Franklin flew a kite, made of a simple silk handkerchief stretched across a cross made of two cedar strips, during a lightning storm. The tail of the kite was made of two materials — the upper end attached to the kite was made of hemp string and attached to a small metal key, while the lower end, held by Franklin, was made of silk. The hemp would get soaked by the rain and conduct electrical charge, while the silk string would remain dry because it is held under cover.

As Franklin observed his flying kite, he saw that the hemp strands stood on end as they began to accumulate electrical charge from the ambient air. When he placed his finger near the metal key, he reportedly felt a sharp spark as the negative charges that had accumulated on the key were attracted to the positive charges in his hand. 

A few publications at the time reported on the experiment. "[Franklin] published a statement about the experiment in the Pennsylvania Gazette , the newspaper he published, on October 19, 1752," Talbott said. He then sent the text of this statement to a patron of the American Philosophical Society named Louis Collinson; Franklin had spent the last few years communicating his theories and proposing his experiments concerning lightning to him.

Franklin referred to the experiment in his autobiography, and other colleagues in Europe wrote about it as well, Talbott said. Notably, the experiment appeared in the 1767 book " History and Present Status of Electricity " by Joseph Priestley, an English chemist. Priestley heard about the kite-and-key experiment from Franklin himself around 15 years after the fact, and in his book, he wrote that it occurred during June 1752. However, exactly when the experiment came to Franklin and when he did it is a matter of debate.

There are some historians who doubt whether Franklin actually did the experiment himself, or merely outlined its possibility. In his book " Bolt of Fate: Benjamin Franklin and His Electric Kite Hoax " (PublicAffairs, 2003), author Tom Tucker stated that Franklin wanted to thwart William Watson, a member of the Royal Society of London and a preeminent electrical experimenter. Watson had sabotaged the publication of some of Franklin's previous reports and had ridiculed his experiments in the Royal Society, Tucker wrote. Could Franklin have felt pressured to invent the kite story to get back at Watson?

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Tucker also noted that Franklin's description of his experiment in the Pennsylvania Gazette was phrased in the future conditional tense: "As soon as any of the Thunder Clouds come over the Kite, the pointed Wire will draw the Electric Fire from them..." Franklin could have simply been saying that the experiment could, in theory, be performed. Given that his statement has a few missing details — Franklin didn't list a date, time or location, for example — it's possible that the American diplomat did not perform the experiment himself.

However, some historians remain unconvinced that the experiment wasn't carried out, pointing to Franklin's great respect for scientific pursuits . Franklin experts, such as the late American critic and biographer Carl Van Doren, also point to the fact that Priestley specified the month in which Franklin performed his experiment, suggesting that Franklin must have given him precise details directly.

Originally published on Live Science.

Jacklin Kwan is a freelance journalist based in the United Kingdom who primarily covers science and technology stories. She graduated with a master's degree in physics from the University of Manchester, and received a Gold-Standard NCTJ diploma in Multimedia Journalism in 2021. Jacklin has written for Wired UK, Current Affairs and Science for the People. 

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An Account of the Kite Experiment

From Carl Van Doren's "Benjamin Franklin," ©1938 by Carl Van Doren

"Before that he had thought of another way of proving his theory, and with the help of his electrical kite had drawn lightning from a cloud. The episode of the kite, so firm and fixed in legend, turns out to be dim and mystifying in fact. Franklin himself never wrote the story of the most dramatic of his experiments. All that is known about what he did on that famous day, of no known date, comes from Joseph Priestley's account, published fifteen years afterwards but read in manuscript by Franklin, who must have given Priestley the precise, familiar details. "As every circumstance relating to so capital a discovery (the greatest, perhaps, since the time of Sir Isaac Newton) cannot but give pleasure to all my readers, I shall endeavour to gratify them with the communication of a few particulars which I have from the best authority. "The Doctor, having published his method of verifying his hypothesis concerning the sameness of electricity with the matter of lightning, was waiting for the erection of a spire [on Christ Church] in Philadelphia to carry his views into execution; not imagining that a pointed rod of a moderate height could answer the purpose; when it occurred to him that by means of a common kite he could have better access to the regions of thunder than by any spire whatever. Preparing, therefore, a large silk handkerchief and two cross-sticks of a proper length on which to extend it, he took the opportunity of the first approaching thunderstorm to take a walk in the fields, in which there was a shed convenient for his purpose. But, dreading the ridicule which too commonly attends unsuccessful attempts in science, he communicated his intended experiment to nobody but his son" — then twenty-one, not a child as in the traditional illustrations of the scene — "who assisted him in raising the kite. "The kite being raised, a considerable time elapsed before there was any appearance of its being electrified. One very promising cloud had passed over it without any effect; when, at length, just as he was beginning to despair of his contrivance, he observed some loose threads of the hempen string to stand erect, and to avoid one another, just as if they had been suspended on a common conductor. Struck with this promising appearance, he immediately presented his knuckle to the key, and (let the reader judge of the exquisite pleasure he must have felt at that moment) the discovery was complete. He perceived a very evident electric spark. Others succeeded, even before the string was wet, so as to put the matter past all dispute, and when the rain had wet the string he collected electric fire very copiously. This happened in June 1752, a month after the electricians in France had verified the same theory, but before he heard of anything they had done."