In June 1752 Benjamin Franklin conducted the Kite Experiment by flying a silk handkerchief under thunder and storm conditions. After conducting the experiment, Franklin was able to prove that lightning from the thunder clouds was nothing but strong bouts of electric sparks.
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Experimental Setup
Benjamin Franklin made a kite from a silk handkerchief and two light strips of cedar. He used silk because a paper kite would have been destroyed in the rain. At the top of the cedar arms, a foot long thin iron wire was attached to attract static electricity. He attached a silk thread to the kite. At the other end of the thread, he tied an iron key. Through the loop of the key he tied a silk ribbon and a long thin wire. He put the other end of the wire into a Leyden jar.
Performing the Kite Experiment
Ben Franklin performed the Kite Experiment in the presence of his son. On an afternoon when thunderclouds were expected, he stood under the window and let the kite soar high towards the sky. When a thundercloud passed over, the electricity from the clouds passed to the kite and travelled down the wet silk string, key and then the wire to the Leyden jar. When Franklin tried to touch the key, he felt a strong shock from a distance.
Precautions While Doing the Kite Experiment
Franklin was very particular about being under some sort of a cover while doing the experiment so that the silk ribbon by which he was flying the kite remained dry. If it got wet, Franklin could have got electrocuted due to the static electricity from the clouds. Franklin was also particular about not letting the kite thread or the key touch any metal frame or door knob. If that had happened, the electricity from the cloud would have passed onto that object and not into the Leyden jar.
Lightning Rod
After the experiment, Franklin was also able to better understand the principle of grounding electricity. So, he reasoned, if electric charge from thunder storms could be conducted to the ground, no harm would be done to the building struck by lightning. He proposed a Lightning Rod made of an iron rod that was long enough to be inserted 3-4 feet deep in the ground at one end, run through the building and rise 3-4 feet above the highest point of the building at the other end. The ground in which the rod was inserted had to be wet.
By late 1752, such lightning rods were installed on many high rise buildings in Philadelphia. And these continue to be used even today. This itself speaks for Benjamin Franklin’s greatness and we don’t need to say anything more about it.
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