lightning rod

A device that protects a building from being struck by lightning, safeguarding the physical integrity of the people occupying it. Lightning rods are also placed on ships and the most diverse types of installations (antennas, electricity pylons, wind turbines...). The most common of all is based on the point-discharge effect and is also known as a Franklin lightning rod, in honor of its inventor: the multi-talented Benjamin Franklin (1706-1790). Thanks to his famous kite experiment, carried out in Philadelphia (USA) on June 15, 1752, he demonstrated that lightning bolts are electrical discharges. The following year (1753) he invented the device. The conventional lightning rod is placed at the highest point of buildings and consists of one or more galvanized steel metal rods, ending in a tungsten point, resistant to the high temperatures generated when lightning strikes it. The ionization of the air at that tip opens the path for lightning coming from storm clouds. The other end is connected to the ground via low-resistance metal conductors. In this way, when lightning strikes the rod, it is quickly transmitted to the ground, preventing the discharge from causing damage to the building's structure. Some lightning rods - also based on the point-discharge effect - are crowned with a kind of ring containing a small amount of a radioactive isotope, whose purpose is to further ionize the air around the device. There are also mesh-type lightning rods - based on the physical principle of the Faraday cage -, consisting of a grounded metal mesh covering buildings entirely. A modern building with a metal structure fulfills that same function, which is why the probability of lightning penetrating it and causing damage inside is reduced to virtually zero.