CBSE Class 7 Science Chapter 8 Notes Winds, Storms and Cyclones
Winds, Storms and Cyclones Class 7 Notes Understanding the Lesson
1. The moving air is called wind.
2. Air exerts pressure on all object. This is called air pressure.
3. Increased wind speed is accompanied by a reduced air pressure.
4. Air moves from a higher pressure region to a lower one. The greater the difference in pressure, the faster the air moves.
5. On heating the air expands and occupies more space. Hence, it becomes lighter. The warm air is, therefore, lighter than cold air. That is the reason that the smoke goes up.
6. At a place, where warm air rises, the air pressure is reduced and the cooler air moves to that place.
7. Wind currents are generated due to uneven heating on the earth. High speed winds are accompanied by reduced pressure.
8. Regions nearer to the equator get maximum heat from the sun. The air in these regions gets warm. The warm air rises, and the cooler air from the region in the 0-30 degrees latitude belt on either side of the equator moves in.
9. At the poles, the air is colder than that at latitudes about 60 degrees. The warm air at these latitudes rises up and the cold wind from the polar regions rushes in, to take its place. In this way, wind circulation is set up from the poles to the warmer latitudes.
10. Due to uneven heating of land and water, in summer, the land near the equator warms up faster and most of the time the temperature of the land is higher than that of water in this oceans.
11. In winter, the direction of the wind is from the land to the ocean.
12. The wind from the ocean carry water and bring rain. It is a part of the water cycle.
13. The monsoon winds carry water and it rains.
14. The winds blow from the oceans towards the land in summer. These are called monsoon winds.
15. There are certain situations, in nature itself, that can sometimes create disasters like thunderstorms and cyclones. They pose threat to humans, animals and plant life.
16. The strong upward rising winds produced by the rising temperature carry water droplets upward where they freeze and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that is called
17. The chain of events of thunderstorm ends with the formation of a very low-pressure system with very high-speed winds revolving around it. It is this weather condition that we call a
18. A cyclone is known by different names in different parts of the world such as ‘hurricane’ in the American continent, ‘typhoon’ in Philippines and Japan, etc.
19. Tornado is a dark funnel-shaped cloud that reaches from the sky to the ground.
20. Self-help is the best help. Therefore it is better to plan in advance and be ready with defence against any approaching cyclone.
Class 7 Science Chapter 8 Notes Important Terms
Anemometer: The instrument that measures the speed of wind is called an anemometer.
Cyclone: A violent storm with wind speed of 120 to 200 km/hr is called a cyclone. It is accompanied by strong winds and heavy rain. It is a very low-pressure system with a very high speed winds revolving around.
Hurricane: A cyclone is known as hurricane in the American continent.
Lightning: A flash of bright light produced by an electric discharge between clouds or between clouds and the ground is called lightning. It occurs when two clouds with unlike charges approach each other.
Low pressure: A condition of the atmosphere in which the pressure is below average. It is also caused when warm air rises up.
Monsoon winds: The wind from the oceans carry water and bring rain. These winds are called monsoon winds.
Pressure: Pressure is exerted by air around us.
Thunderstorms: The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that is called thunderstorm.
Tornado: A tornado is a dark funnel-shaped cloud that reaches from the sky to the ground. It may form within a cyclone.
Typhoon: A cyclone is called a typhoon in Philippines and Japan.
Wind flow pattern: Winds flow from oceans towards the land in summer and from land to oceans in winter.