Air Pressure | Class 7 | Geography | Chapter 4 | Maharashtra State Board
Welcome to this informative video where we will be exploring the concept of air pressure. Through a series of engaging activities, we will help you understand the relationship between air temperature and air pressure. We will also introduce you to various pressure belts such as the Equatorial low pressure belt, Mid-latitudinal high pressure belts, Sub-polar low pressure belts, and Polar high pressure belts. You will learn about the unique characteristics of each pressure belt and how they impact global weather patterns. Additionally, we will explain what Isobars are and how they can be used to visualize air pressure on a map. Through the use of clear visuals and easy-to-understand explanations, you will gain a solid understanding of air pressure and its impact on weather patterns. So, get ready to explore the fascinating world of air pressure with us! By the end of the video, you will have gained valuable knowledge and insights into this important scientific concept.
Questions & Answers
Q.1. Give reasons.
1. Air pressure decreases with increasing altitude.
Ans.
The proportion of dust in the air, water vapour, heavy gases, etc. is higher in the air and closer to the surface of the earth.
This proportion decreases with increasing altitude.
As one moves higher and higher from the surface of the earth, the air becomes thinner and thinner.
As a result, the air pressure decreases with increasing altitude.
2. Pressure belts oscillate.
Ans.
The duration and the intensity of sun rays varies during particular periods of the year in both the hemispheres.
So, the locations of the temperature zones and the pressure belts dependent on the sun’s heat also vary.
This change is of the order of 5° to 7° towards the north in Uttarayan1 and 5° to 7° south in Dakshinayan2.
In this way pressure belts oscillate.
Q.2. Give short answers to the following questions.
1. What effect does temperature have on air pressure?
Ans.
Temperature and air pressure are closely related. Wherever the temperature is high, the air pressure is low.
As the temperature rises, the air gets heated, expands, and becomes lighter.
This lighter air in the vicinity of the earth’s surface starts moving up towards the sky.
As a result, the air pressure in such areas decreases.
2. Why is the subpolar low-pressure belt formed?
Ans.
Due to earth’s curvature, the area between two parallels gets reduced as we move towards the poles.
This results in lesser frictional of the air with the earth’s surface.
Air in this region is thrown out because of this reduced friction and also because of the earth’s rotational motion.
This leads to the development of a low-pressure belt in the sub polar region i.e. in area between 55° & 65° parallels in both the hemispheres.
Q.3. Write notes on.
1. Mid-latitudinal high-pressure belts.
Ans.
The heated air from the equatorial region becomes lighter, starts ascending and after reaching higher altitudes, moves towards the polar region, i.e., towards the North and the South Pole.
Due to low temperatures at the higher altitudes, the air cools down and becomes heavier.
This heavier air descends down in both the hemispheres in the region between 25° to 35° parallels.
This leads to the formation of high pressures, belts in these parallels of latitudes in both the hemispheres.
This air is dry, hence the region does not get rainfall.
Consequently, most of the hot deserts on the earth are found in these regions.
2. Horizontal distribution of air pressure.
Ans.
The heat received from the sun is uneven in different regions.
The distribution of temperature is uneven from the equator to the poles.
This difference can lead to difference in air pressure.
There are four air pressure belts formed on the earth surface.
Equatorial low-pressure belt between 5°N and 5°S parallels as the temperature is high here.
Mid latitudinal high-pressure belt between 25° and 35° parallels due to descending heavier air.
Subpolar low-pressure belt formed between 55° and 65° parallels due to friction and rotation.
Polar high-pressure belt formed between 80° and 90° parallels due to low temperatures.
Q.4. Fill in the gaps with the appropriate option.
At higher altitudes air becomes thinner. (thicker, thinner, hotter, more humid)
Air pressure is expressed in millibars. (millibars, millimetres, millilitres, milligrams)
On the earth, air pressure is uneven. (uniform, uneven, high, low)
The equatorial low pressure belt spreads between 5° North and 5°South parallel. (Equatorial low, Polar high, Subpolar low, Mid-latitudinal high)
Q.5. How does a high-pressure belt get formed near 30° parallel? Why does this region have hot deserts?
Ans.
The heated air from the equatorial region becomes lighter, starts ascending and after reaching higher altitudes, moves towards the polar region, i.e., towards the North and the South Pole.
Due to low temperatures at the higher altitudes, the air cools down and becomes heavier. This heavier air descends down in both the hemispheres in the region between 25° to 35° parallels.
This leads to the formation of high pressures belts in these parallels of latitudes in both the hemispheres.
This air is dry, hence the region does not get rainfall. Consequently, most of the hot deserts on the earth are found in these regions.
Q.6. Draw a neat diagram showing pressure belts. Label the diagram.
E X T R A
Q.1. Fill in the blanks choosing the correct option from the brackets.
The latitudinal extent of the temperate zones is much larger while belts are narrower.
The extent of air pressure belt is up to 10° parallel.
Pressure belts are formed between the equator and the pole.
The sun rays fall perpendicular between the Tropic of Cancer and Tropic of Capricorn.
Due to the earths curvature, the area between two parallels gets reduced as we move towards the poles.
The air pressure at sea level is 1013.2 millibars.
Q.2. Answer the following questions in one or two sentence.
1. Which factors influence air pressure?
Ans. The altitude of a region, temperature of the air and the amount of water vapour in the air are some factors influencing air pressure.
2. What is the extent of air pressure belt?
Ans. The extent of air pressure belt is generally upto 10° parallel.
3. What is the latitudinal extent of temperate zone?
Ans. The latitudinal extent of temperate zone is from 23°30’N to 66°30’N and 23° 30’S to 66° 30’S.
4. What is the temperature in the polar region?
Ans. In both the polar regions, the temperature is below 0°C throughout the year.
5. Why do all things in and on the earth stay earth bound?
Ans. All things in and on the earth stay bound due to the earth’s gravity.
6. Why are temperature zones created on the surface of the earth?
Ans. The heat received from the sun is uneven in different regions. Hence, the distribution of the temperature is uneven from the equator to the poles. As a result, temperature zones are created.
7. Most of the hot deserts on the earth are found in which region?
Ans. Most of the hot deserts on the earth are found in the mid latitudinal high pressure belt i.e. between 25° to 30° parallels in both hemispheres.
Q.3. Give reasons.
1. Air pressure is maximum at sea level.
Ans.
All things in and on the earth stay earthbound because of the earth’s gravity. This includes air which is in the gaseous form.
Due to the earth’s gravity, air is pulled to the earth’s surface.
Also as one moves higher & higher from the earth’s surface the air becomes thinner & thinner.
Therefore, the air pressure is maximum at sea level.
2. A low-pressure belt is formed near the equator.
Ans.
The sun rays can be perpendicular between the Tropic of Cancer and the Tropic of Capricorn.
The temperature is higher in this region.
Hence, air in this region gets heated, expands and becomes lighter and moves towards the sky.
As this process operates continuously, a low pressure belt gets formed in the central part of this region between the parallels 5° N and 5° S, near the equator.
3. High pressure belt is formed near the polar region.
Ans.
In both the polar regions, the temperature is below 0° throughout the year.
The air is cold.
Hence, high pressure belt is formed in the polar region.
4. Low pressure belt is observed between 55° and 65° parallels in both the hemispheres.
Ans.
Due to the earth’s curvature, the area between two parallels gets reduced as we move towards the poles. This results in lesser friction of the air with the earth’s surface.
The air between 55° and 65° parallels is thrown out because of the reduced friction and also due to the earth’s rotation.
Therefore, a low pressure belt is observed between 55° and 65° parallels in both the hemispheres.
5. Temperature and air pressure are closely related.
Ans.
Wherever the temperature is high, the air pressure is low. As the temperature rises the air gets heated, expands, and become lighter.
Thin, lighter air in the vicinity of the earth’s surface starts moving up towards the sky. As a result the air pressure in such area decreases.
Hence, temperature and air pressure are closely related.
6. Most of the hot deserts on the earth are found in mid-latitudinal high pressure belts.
Ans.
The air in mid-latitudinal high-pressure belt (between 25° to 35° parallels in both hemisphere) is found to be dry.
The amount of water vapour is very low and hence, this region gets extremely scarce or no rainfall.
Consequently, most of the hot deserts on the earth are found in mid latitudinal high-pressure belts.
Q.4. Give short answers to the following.
1. What are the effects of air pressure?
Ans. Air pressure has the following effects.
Origin of winds.
Generation of storms.
Convectional type of rain.
2. What is the difference between the temperature zones and pressure belts?
Ans.
The difference between the temperature zones & pressure belts is that the latitudinal extent of temperature zones is much larger while pressure belts are narrower.
For example, the Temperate zone extends from 23°30′ to 66°30′ in both hemisphere. Compared to this the pressure belt has limited extent which is generally upto 10° parallel.
Also the temperature zones are continuous and spread from the equator to the poles from Torrid to Frigid.
Pressure belts are not continuous and areas of high & low pressure are found in different regions from the equator to the poles.
3. How does a high pressure belt get formed near 30° parallel? Why does this region have hot deserts?
Ans.
The heated air from the equatorial region becomes lighter, starts ascending and after reaching higher altitudes, moves towards the polar region, i.e., towards the North and the South Pole.
Due to low temperatures at the higher altitudes, the air cools down and becomes heavier. This heavier air descends down in both the hemispheres in the region between 25° to 35° parallels.
This leads to the formation of high pressures belts in these parallels of latitudes in both the hemispheres.
This air is dry, hence the region does not get rainfall. Consequently, most of the hot deserts on the earth are found in these regions.
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