How do lightning rods prevent lightning strikes from reaching people? Premium
The Hindu
Climate change increases lightning strikes globally, making lightning rods crucial for protection against deadly strikes.
Climate change is making lightning strikes around the world more common and deadlier. Every year, around 24,000 people around the world are killed by such strikes; in India, lightning strikes killed 2,887 people in 2022. There have been petitions to declare this phenomenon a natural disaster in India so that its survivors can access institutional mechanisms for protection and rehabilitation. Against this backdrop, lightning rods are important for their ability to keep lightning away from people.
Lightning is an electrical discharge between charged particles in a cloud and the ground. Objects can be classified as electrical conductors or insulators, but this depends on the electrical energy acting on the object. For example, the air around us is an electrical insulator: it doesn’t transport electric charges. But if it is subjected to a high voltage of around 3 million V/m, its insulating properties break down and it can transport a current.
Lightning strikes are possible because electrical charges can build up in a cloud beyond the ability of air to keep resisting their movement.
While a lightning strike occurs between a cloud and an object on or near the ground, it takes the path of least resistance, which means it moves towards the closest object with the highest electric potential.
“The reason lightning strikes the rod has to do with its shape. Lightning rods are pointy and pointed things create stronger electric fields near them,” IIT Kanpur assistant professor of physics Adhip Agarwala said. “It’s like saying the flow of water speeds up near a nozzle. The electric field is the force that acts on molecules of air, so it becomes strongest near the lightning rod. This force ionises the air near the rod first and provides a route for the current to flow.”
Think of a lightning strike as the extended hand of someone who wants to be pulled out of a pool. If there are many hands offering to help, the lightning’s hand will reach for the strongest one. A lightning rod is an electrical conductor that takes advantage of this fact with one addition: engineers install it on building-tops in a way that it’s the first hand the lightning encounters on its way down. This is also why it’s risky to stand under trees in an otherwise open field, like a farm.
Heat energy always flows from a warmer object to a cooler object. Liquid water flows from a place with a higher gravitational potential to a lower one. Similarly, an electric current flows from a place with higher electric potential to a place with lower electric potential.
