As part of his studies on the phenomenon of electricity, Benjamin Franklin invented the lightning rod in 1749. The lightning rod is, of course, a staff of highly conductive material (such as copper) which sits on the top of a building and which is connected to the ground through a wire. A lightning bolt will normally strike the highest object in the area, which would be the rod, and the current will harmlessly go into the ground through the wire as the path of least resistance. Without the presence of the rod, the bolt can pass directly through the building materials themselves and cause fire, explosion, and electrocution.
Franklin needed a simple way of demonstrating this principle, and he, as a result, developed the "thunder house." The thunder house was a simple model of a building with loosely connected walls or roof panels as well as a lightning rod on the top and a small amount of gunpowder concealed in the interior. Franklin would first run a metal chain from the rod to the ground (a metal panel on which the house was mounted) and then touch an electrical charge to the rod, Nothing would appear to happen, as the current would pass uneventfully through the chain into the ground. Franklin would then remove the chain and repeat the experiment. This time, the charge would pass through the house itself, set off the gunpowder, and "destroy" the dwelling, much to the awe and delight of the onlookers.
When I was a youth, most homes had grounded television antennas mounted on the roof which served very nicely as lightning rods. Now that external antennas are for the most part extinct, what protects a modern house from the effects of a lightning strike? As far as I can tell, nothing except luck.
To see Ben Franklin demonstrate his thunder house, click here.
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