Chapter 8 – Winds, storms and cyclones

These NCERT Class 7 Science Chapter 8 notes explain how air moves to form winds and how strong winds can lead to storms and cyclones. The chapter helps students understand air pressure, effect of heat on air, and reasons behind fast-moving winds.

Winds, Storms and Cyclones also explains natural events like thunderstorms, lightning, cyclones, and tornadoes. It highlights their effects and the importance of safety measures and disaster management.

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1. Introduction: why winds and storms are studied

•  Air is present all around us and its movement affects weather.
•  Strong winds can cause storms and cyclones, leading to loss of life and property.
•  Calm air is harmless, but moving air can be powerful.

2. Air pressure

•  Air has weight, so it exerts pressure.
•  When air moves fast, pressure decreases.
•  Activities like inflating a balloon show air pressure.
•  The upside-down glass experiment proves air pressure.

3. High-speed winds

•  Wind is simply moving air.
•  Faster wind creates a greater pressure difference.
•  High-speed winds can lift light objects.
•  Roof sheets may blow away during storms.

4. Wind and atmospheric pressure

•  Air always moves from high pressure to low pressure areas.
•  Uneven heating of the Earth creates pressure differences.
•  Air moves to fill empty space.

5. Effect of heat on air

•  Warm air becomes lighter and rises upward.
•  Cold air becomes heavier and sinks down.
•  Continuous air movement creates wind.

6. Thunderstorms

•  Thunderstorms occur due to rapid rising of warm air.
•  Cumulonimbus clouds are formed during thunderstorms.
•  They bring heavy rain, thunder, lightning, and strong winds.

7. Lightning

•  Lightning is a sudden electric discharge.
•  It occurs due to charge separation in clouds.
•  One should avoid open fields and tall trees during lightning.

8. Cyclones

•  A cyclone is a violent rotating storm.
•  Cyclones form over warm ocean water.
•  Air moves towards a low-pressure centre.
•  The centre is the eye of cyclone, which is calm.
•  Surrounding areas have very strong winds.

9. Conditions for cyclone formation

•  Warm ocean water provides energy.
•  A low-pressure area is necessary.
•  High wind speed supports rotation.
•  Presence of moist air helps cyclone growth.

10. Effects of cyclones

•  Cyclones cause heavy rainfall and floods.
•  They destroy houses, crops, and infrastructure.
•  There is loss of human and animal life.
•  In India, coastal states like Odisha, West Bengal, Andhra Pradesh, and Tamil Nadu are affected.

11. Tornado

•  A tornado is a very strong rotating wind.
•  It forms over land, not oceans.
•  Tornadoes are smaller but more destructive than cyclones.

12. Destruction caused by storms

•  Trees may be uprooted.
•  Electric poles and lines get damaged.
•  Flooding disrupts normal life.
•  Communication systems may fail.

13. Safety measures before a cyclone

•  Secure houses properly.
•  Store food and drinking water.
•  Keep an emergency kit ready.

14. Safety measures during a cyclone

•  Stay indoors and remain safe.
•  Switch off electricity to avoid accidents.
•  Avoid flood water completely.

15. Safety measures after a cyclone

•  Avoid damaged buildings.
•  Drink only clean water.
•  Follow government instructions strictly.

16. Disaster management

•  Early warning systems help reduce damage.
•  Government agencies manage evacuation and relief.
•  Community participation is very important.

17. Important keywords with simple definitions

•  Air pressure – force exerted by air.
•  Wind – moving air.
•  Storm – strong wind with rain or dust.
•  Thunderstorm – storm with thunder and lightning.
•  Cyclone – large rotating storm over sea.
•  Tornado – violent rotating wind over land.
•  Eye of cyclone – calm centre of a cyclone.

Understanding NCERT Class 7 Science Chapter 8 – Winds, Storms and Cyclones is important to learn how air movement affects weather and causes natural disasters. The chapter clearly explains cyclones, thunderstorms, and safety practices.

These concepts are very useful for school examinations and foundation-level science preparation. Students should next read Chapter 9: Soil to understand soil formation, types of soil, and their importance.

FAQs

Q1. What is explained in NCERT Class 7 Science Chapter 8?
The chapter explains winds, air pressure, storms, cyclones, and safety measures.

Q2. What causes wind to move?
Wind moves due to differences in air pressure created by uneven heating of the Earth.

Q3. What is a cyclone?
A cyclone is a violent rotating storm that forms over warm ocean water.

Q4. What is the eye of a cyclone?
The eye of a cyclone is the calm central region surrounded by strong winds.

Q5. Why is NCERT Class 7 Science Chapter 8 important for exams?
It explains natural phenomena and disaster safety, which are important for school and foundation-level exams.

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