GS-2: Important Geophysical phenomena such as earthquakes, Tsunami etc
GS-3: General Science
Lightning
Context: Recently, thirty people were killed in separate incidents of lightning in various parts of India. Lightning is the biggest contributor to accidental deaths due to natural causes.
What is lightning?
It is the process of occurrence of a natural ‘electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud’, accompanied by a bright flash and sound, and sometimes thunderstorms.
How does lightning occur?
It is a result of the difference in electrical charge between the top and bottom of a cloud.
As water vapour moves upwards in the cloud, it condenses into water due to decreasing temperatures. A huge amount of heat is generated in the process, pushing the water molecules further up.
As they move to temperatures below zero, droplets change into small ice crystals. As they continue upwards, they gather mass, until they become so heavy that they start descending.
It leads to a system where smaller ice crystals move upwards while larger ones come down. The resulting collisions trigger release of electrons, in a process very similar to the generation of electric sparks.
The moving free electrons cause more collisions and more electrons leading to a chain reaction.
The process results in a situation in which the top layer of the cloud gets positively charged while the middle layer is negatively charged.
In little time, a huge current, of the order of lakhs to millions of amperes, starts to flow between the layers.
It produces heat, leading to the heating of the air column between the two layers of cloud. It is because of this heat that the air column looks red during lightning.
The heated air column expands and produces shock waves that result in thunder sounds.
The Earth is a good conductor of electricity. While electrically neutral, it is relatively positively charged compared to the middle layer of the cloud. As a result, an estimated 20-25% of the current flow is directed towards the Earth. It is this current flow that results in damage to life and property.
Do you know?
Lightning has a greater probability of striking raised objects on the ground, such as trees or buildings.
Lightning Conductor is a device used to protect buildings from the effect of lightning.
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.
The most lightning activity on Earth is seen on the shore of Lake Maracaibo in Venezuela.
Lightning incidents is directly related to the climate crisis, and the availability of more moisture over land due to global warming.
An increase of one degree Celsius would increase the frequency of lightning strikes by 12%, warned California University in a study published 2015.
