The lightning rod is a metal strip or rod, usually of copper or similar conductive material, set up and used to protect tall and isolated structures (such as the roof of a building or the mast of a vessel) from lightning damage. The lightning rod is also called lightning conductor, lightning arrester, lightning discharger or lightning protector.
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It is commonly believed, erronously, that a sharp pointed rod at the peak is the best means to conducts the current to the ground. A rounded or spherical topped rods at the peak, and connected with the earth or water below, for the purpose of protecting the building or vessel from lightning is the best means to conducts the current to the ground through a low-resistance cable where it is dissipated. Lightning rod also posses a short circuit to the ground that is interrupted by a thin nonconductor over which lightning jumps.
In telegraphy, the lightning rod device is used for preventing injury by lightning to an individual or an elkectronics instrument. The lightning rod is placed where the wire enters a structure.
In Europe, the original lightning rod was invented contemporaneously with but independently of Benjamin Franklin by the Czech theologian and natural scientist Vaclav Prokop Divis (1698-1765).
In America, the original lightning rod was invented by Benjamin Franklin as part of his groundbreaking explorations of electricity. Franklin speculated that with an iron rod sharpened to a point at the end "the electrical fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike..."
Franklin had speculated about lightning rods for several years before his reported kite experiment. In fact, the rumored Franklin's kite experiment took place because he was tired of waiting for Christ Church in Philadelphia to be completed so he could place a lighting rod on top of it.
There was some resistance from churches who felt that it was defying divine will to install these rods. Franklin countered that there is no religious objection to roofs on buildings to resist precipitation, so lightning, which he proved is simply a giant electrical spark, should be no different. The Roman Catholic Church dropped its objection to the device in 1769 when the Church of San Nazaro, near Venice, was struck by lightning. The resulting fire ignited the 200,000 pounds of gunpowder that were being stored there at that time, creating a massive explosion which destroyed one sixth of the city of Brescia and killed 3,000 people.
The lightning rod not only protects buildings. In the 19th century it also became a symbol of American ingenuity and a decorative motif. Lightning rods were often embellished with non-functional glass balls (now prized by collectors) and incorporated into weather vanes.
In the year of 1918 (on May 14), Nikola Tesla recieves the patent US1266175 for Lightning-Protectors. It a novel and advantageous construction of a protector in accord with the true character of the phenomena of lightning. It corrects Benjamin Franklin's hypothesis (rounded or spherical topped rods are better than the pointed rods proposed by Franklin), and subsequent construction, for lightning protectors.
Construction and Uses
History
Europe
America
1918
Quotation
External Link