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๐ฌ Think about it
A flash splits the sky, then a crack of thunder makes you jump. We've all felt the drama of a thunderstorm. But where does that flash come from — how does a cloud build up enough electricity to light up the sky? The clue is rubbing, just like in the last chapter.
How does a storm form?
- Heated land warms the moist air, which becomes lighter and rises, leaving low pressure.
- Cooler air rushes in, gets heated and rises too — a continuous wind circulation.
- The rising air cools, its moisture condenses into water droplets and clouds.
- Droplets merge into heavier drops that fall as rain, hail or snow; strong winds with rain make a storm.
How a Storm Forms
Warm air rises
Heated moist air rises, leaving a low-pressure area
↓
Clouds form
Rising air cools; moisture condenses into droplets and clouds
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Heavy drops fall as rain; strong winds with rain = a storm
How do clouds become electrically charged?
- Strong winds blow water droplets and ice particles up and down inside the cloud.
- These rub against each other and develop static electric charges.
- Lighter, positively charged ice particles gather at the top of the cloud.
- Heavier, negatively charged water droplets gather at the bottom — a charge separation.
What is lightning, and what is a thunderstorm?
- Air is normally an insulator and keeps opposite charges apart.
- When the charge build-up is very large, the air's insulation breaks down.
- A sudden flow of charges gives a bright flash called lightning.
- Lightning heats the air, which expands and makes a loud sound — thunder; a storm with thunder and lightning is a thunderstorm.
๐ Staying Safe — Lightning precautions
- Stay away from tall objects like trees and poles.
- Find a low-lying open area and crouch down; minimise contact with the ground.
- Do not lie flat on the ground.
- Avoid an umbrella with a metallic rod.
- If you are in water, get out of it.
- Inside a bus or a car you are comparatively safer.
โก A step further
- Local thunderstorms occur in parts of India before the monsoon.
- They are called Kalboishakhi in West Bengal, Bihar and Jharkhand, and Bordoisila in Assam.
- They help kharif crops grow.
- In Kerala, Karnataka and Tamil Nadu they are called mango showers, helping mangoes ripen; in Karnataka they also help coffee plants grow.
โก Ever heard of ...
- A lightning conductor is a metal rod fixed along a building's walls during construction.
- Its pointed end is kept higher than the highest point of the building.
- Its other end is buried deep in the ground.
- It gives electric charges an easy path into the ground, protecting the building.
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Test Yourself
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What is a storm?
View Answer
Strong winds accompanied by rain. -
How do charges develop in a cloud?
View Answer
Strong up-and-down winds rub ice particles and water droplets, building static charges. -
What is lightning?
View Answer
A bright flash from a sudden flow of charges when the air's insulation breaks down. -
What causes thunder?
View Answer
Lightning heats the air, which expands rapidly and produces a loud sound. -
What does a lightning conductor do?
View Answer
It gives lightning charges an easy path into the ground, protecting the building.
Important Definitions
- Storm — Strong winds accompanied by rain.
- Lightning — A bright flash of light from a sudden flow of charges when air's insulation breaks down.
- Thunder — The loud sound made when lightning heats and rapidly expands the air.
- Thunderstorm — A storm accompanied by lightning and thunder.
- Lightning conductor — A metal rod on a building that safely carries lightning charges into the ground.
๐ NCERT Question 6 — Would lightning occur if air
Would lightning occur if air and clouds were good conductors of electricity? Give reasons.
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๐ NCERT Question 11 — What is a thunderstorm?
What is a thunderstorm? Explain the process of its formation.
View Answer →
๐ NCERT Question 12 — Explain the process that causes
Explain the process that causes lightning.
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