A lightning rod is a metal rod or wire fixed to an exposed part of a building or other tall structure to divert lightning harmlessly into the ground.
Lightning rods were originally developed by Benjamin Franklin. A lightning rod is very simple — it’s a pointed metal rod attached to the roof of a building. The rod might be an inch (2 cm) in diameter. It connects to a huge piece of copper or aluminum wire that’s also an inch or so in diameter. The wire is connected to a conductive grid buried in the ground nearby.
Lightning rods intercept this voltage, providing a safe path for lightning current into the ground. They do not decrease the likelihood your home may be struck, but provide a direct path to ground, preventing damage to your home from fire, explosion, and electrical surges that can result from lightning strikes.
There is no good reason why lightning rods (and the associated assembly consisting of a connection to earth and a ground rod) are not routinely added to houses. … However, most high buildings and other structures do have some kind of lightning protection system incorporated into them.
If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through a wire, instead of passing through the structure, where it could start a fire or cause electrocution. Lightning rods are also called finials, air terminals, or strike termination devices.
Myth: Lightning rods attract lightning.
Fact: Definitely not! A lightning protection system simply intercepts a lightning strike and provides a path to ground for discharging the dangerous electricity.
The purpose of lightning rods is often misunderstood. Many people believe that lightning rods “attract” lightning. It is better stated to say that lightning rods provide a low-resistance path to ground that can be used to conduct the enormous electrical currents when lightning strikes occur.