Maharashtra Board Class 7 Geography Solution Chapter 4 – Air Pressure
Balbharati Maharashtra Board Class 7 Geography Solution Chapter 4: Air Pressure. Marathi or English Medium Students of Class 7 get here Air Pressure full Exercise Solution.
|Maharashtra Class 7|
- 1. Give reasons:
(1) Air pressure decreases with increasing altitude.
ans. 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 heat received from the uneven in different regions. Hence the distribution of the temperature is uneven from the equator to the poles. As a result, pressure belts oscillate.
- 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 vicnity 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 earths 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. Air in this region is thrown out because of this reduced friction and also because of the earth’s rotational motion. This lead to the development of the subpolar low pressure belt.
- 3. Write notes on:
(1) Mid-latitudinal high pressure belts
ans. The heated air 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 degree to 35 degree 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 horizontal distribution of air pressure across the latitudes is characterised by high or low pressure belts.
Equatorial low pressure belt: Temperature is high in this region. Hence air in this region gets heated, expands, become 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 degree north and 5 degree south.
Mid-latitudinal high pressure belts:- The heated air becomes lighter, starts ascending and after reaching higher altitudes, moves towards the polar region. Due to low emperatures 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 degree to 35 degree parallels.
Sub-polar low pressure belts: 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. This condition is observed in the area between 55 degree and 65 degree parallels in both the hemispheres.
Polar high pressure belts: In both the polar regions, the temperature is below ) degree C throughout the year. Hence, here the air is cold. As a result high pressure belts get formed. These are called polar high pressure belts. They generally occupy the area between 80 degree and 90 degree parallels in both the hemispheres.
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 degree to 7 degree towards north in Uttarayan, and 5 degree to 7 degree south in Dakshinayan. This is called the oscillation of pressure belts.
- 4. Answer
(2) milli bars
(4) Equatorial low.
Extra Questions and Answers Notes
1.) How does temperature control air pressure?
A:- A disproportionate relationship between temperature and air pressure is observed. Because as the temperature rises the air becomes lighter expands and the air temperature increase. This warm light air continues to rise above the earth’s surface .As a result the air pressure in the area gradually decreases.
2.) The equatorial low pressure belt extends from __________ degrees to ___________ .
A:- 5° north and 5° south.
3.) Why are most deserts seen in mid latitude high pressure zones ?
A:- The air in the equatorial low pressure zone heats up and becomes lighter and the air continues to rise. As this air gradually rises to the higher altitudes it comes in contact with cold air and that air cools and becomes heavier. This heavy wind descends between 25 and 35 degrees latitude in two hemispheres. This leads to the formation of high pressure zones in the two hemispheres. As there is no water vapor in this downward air, it is dry in nature, so there is almost no rainfall in this region. Due to the lack of rainfall most of the deserts
seen in this region .
4.) The temperature in the polar region is ____________ throughout the year.
A:- Below 0°C
5.) What is oscillation of pressure belts ?
A:- In both hemispheres the duration and intensity of sunrise varies at certain times of the year. As a result, the locations of the temperature zones and the pressure belts dependent on the sun’s heat also vary. This change moves 5 – 7 degrees north in the case of uttarayan and 5 -7 degrees south in the case of dakhinayan. This is called oscillation of pressure belts.
6.) What is the main difference between temperature zone and air pressure belt ?
A:- The main difference between the temperature zone and the air pressure belt is –
The temperature region is distributed from the equatorial region to the pole in a continuous manner.
Such as – Very high temperature zone, high temperature zone, moderate temperature zone, low temperature zone etc. But the air pressure belt is divided from the equator to the pole. Such as – Equatorial low pressure belt, Mid-latitudinal high pressure belts.
7.) The line that joins the places of equal pressure on the map is called an – ( isobar / isotherm / isohaline / contour )
8.) Air pressure is measured in units of (cm / millibars / inch / none of the above )
9.) The air pressure at sea-level is _________________ millibars.
A:- 1013.2 millibars.
10.) Which instrument is used to measure air pressure ?
A:- Air pressure is measured with the help of barometer.
11.) Air pressure is maximum at ________________ .
A:- Sea level