Getting a shock from a doorknob after rubbing your foot on a carpet floor, resultsfrom discharge. Discharge occurs when electrons on the hand are quickly pulled to thepositively charged doorknob. This movement of electrons, which is felt as a shock, causes the body to lose negative charge. Electric dischargetakes place in a medium, mostly gases.Lightning is another example of discharge that takes place in clouds.
Lightning is produced by discharge of electricity from cloud to cloud or from cloudto ground. During thunderstorm air is moving upward rapidly. This air which moves rapidly,carries small ice crystals upward. At the sametime, small water drops move downward.When they collide, ice crystals become positively charged and move upward and the water drops become negatively charged andmove downward. So the upper part of the cloud is positively charged and the lower partof the cloud is negatively charged. When they Come into contact, electrons in the water drops are attracted by the positive charges in theice crystals. Thus, electricity is generated and lightning is seen.
Sometimes the lower part of the cloud which is negatively charged comes into contact with the positive charges accumulated nearthe mountains, trees and even people on the earth. This discharge produces lot of heat and sparks that results in what we see as lightning.Huge quantities of electricity are discharged in lightning flashes and temperatures of over30,000°C or more can be reached. This extreme heating causes the air to expand explosively fast and then they contract. This expansion andcontraction create a shock wave that turns intoa booming sound wave, known as thunder.
Lightning's extreme heat will vaporize the water inside a tree, creating steam that may burnOut the tree.
Sometimes lightning may be seen before the thunder is heard. This is because the distance between the clouds and the surface is very long and the speed of light is much faster than thespeed of sound.
During lightning and thunder, we should avoid standing in ground and open spaces. You should make yourself as small as possible by squating. It is however safe to stay inside a car because the car acts as a shield and protects us from the electric field generated by the storm.
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