| Reference Book | Ratna Sagar Integrated Social Science |
| Class | Class 7 |
| Category | Geography |
| Chapter Number | Chapter 6 |
| Chapter Name | Weather and Climate |
A) Tick (✓) the correct answers.
1) The amount of Solar energy received by the Earth is called
a) insolation ✓
b) solar energy
c) radiation
d) temperature
2) Which of the following temperature scales is used in India ?
a) Celsius
b) Kelvin
c) Richter
d) Fahrenheit ✓
3) Which of the following instruments is not used to measure winds?
a) Barometer ✓
b) Anemometer
c) Wind vane
d) Beaufort scale
4) Which of the following is not a periodic wind ?
a) Land breeze
b) Sea breeze
c) Loo ✓
d) Monsoon
5) Which of the following is not a local wind ?
a) Harmattan
b) Loo
c) Chinook
d) Monsoon ✓
6) Which of the following is not a type of cloud ?
a) Cumulus
b) Cirrus
c) Sleet ✓
d) Stratus
B) Fill in the blanks
1) The temperature of air decreases from equator towards the poles
2) The atmospheric pressure is maximum at the mean sea level.
3) The direction of wind can be found with the help of a wind vane.
4) Plants and animals provide moisture to the atmosphere through transpiration.
C) Distinguish between the following :
1) Weather and climate
| Weather | Climate |
| 1) It is defined as the state of temperature, atmospheric pressure, winds, humidity, precipitation etc in the atmosphere at a given place and time. | It is defined as the average overall condition of the temperature, atmospheric pressure, winds, humidity, precipitation over a large region for a long period of time. |
| 2) It occurs in a place within a short period. | It takes place over long period of time. |
| 3) Change in weather is a continuous process. | Climate of a place remains same almost year after year. |
2) Insolation and terrestrial radiation
| Insolation | Terrestrial radiation |
| 1)The amount of solar radiation received on the surface of the earth’s surface is called insolation. | The heat which was absorbed during the day, is radiated back is called terrestrial radiation. |
| 2) It travels in short waves. | It travels in long waves. |
3) Absolute and relative humidity
| Absolute humidity | Relative humidity |
| 1)The actual amount of water vapours present in air is called humidity or absolute humidity. | It is defined as the ratio between the actual amount of water vapours present in the air at a given temperature and the maximum capacity of the air to hold moisture at that temperature. |
4) Condensation and precipitation
| Condensation | Precipitation |
| 1) When moist air rises upwards, it becomes cool and the water vapour changes into small drops of water. The process is called condensation. | When small water drops join together, they grow in size until they are unable to float in the air. Then they fall down as raindrops or flakes of snow. This process is called precipitation. |
| 2) The important forms of condensation are dew, fog and clouds. | The important forms of precipitation are rain, drizzle, snow, hailstone. |
D) Write short answers for the following questions :
1) Solar radiation
The Sun radiates heat and light energy. This is called solar radiation. It is the main source of heat and light for us. However only a very small part of the solar radiation is able to reach the Earth’s surface. The amount of solar radiation received by the Earth’s surface is called insolation. The amount of insolation received on the surface of the Earth varies from place to place and from time to time. The Earth’s surface absorbs maximum solar radiation during the day.
2) Heat zones
On the basis of the amount of heat received by the Earth’s surface, the world has been divided into three heat zones.
a) Torrid zone : In the Northern hemisphere, it is between Equator and Tropic of cancer. In Southern hemisphere, it is between Equator and Tropic of capricorn. It receives maximum isolation, Sun rays are almost vertical throughout the year and it is the hottest part of the Earth.
b) Temperate zone : In the Northern hemisphere, it is between Tropic of cancer and Arctic circle. In Southern hemisphere, it is between Tropic of capricorn and Antarctic circle. It receives moderate isolation and is neither too cold nor too hot.
c) Frigid zone : In the Northern hemisphere, it is between Arctic circle and North Pole. In Southern hemisphere, it is between Antarctic circle and South Pole. It receives minimum insolation, Sun’s rays are slanting throughout the year and it is the coldest part of the Earth.
3) Local winds
In many parts of the world, winds with special characteristics blow over small areas. These winds blow for a short time. Such winds are called local winds. Most of them are seasonal and their names are usually derived from the regional language.
4) Clouds
When small drops of water condenses around dust or smoke particles in the air, the mass is called cloud. Clouds move from one place to another even by lighter air movement. Depending upon their shape and the height at which they are formed, there are three types of clouds.
E) Give short answers for the following questions.
Que 1 What are the main elements of weather and climate?
Ans The six main elements of weather and climate are temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.
Que 2 How is the atmosphere heated?
Ans The air resting over the Earth’s surface gets heated due to contact with the hot surface of the earth. This heat is further transmitted to the upper layers and the atmosphere is heated.
Que 3 What do you mean by humidity in the atmosphere? How do we express it?
Ans The actual amount of water vapours present in the air is called humidity. An important and useful way of expressing the level of humidity is in the terms of relative humidity. It is defined as the ratio between the actual amount of water vapour present in the air at a given temperature and the maximum capacity of the air to hold moisture at that temperature.
Que 4 Name the different forms of condensation and precipitation.
Ans The important forms of condensation are dew, fog and clouds.
The important forms of precipitation are rain, drizzle, snow, hailstone.
F) Give long answers for the following questions.
Que 1 Explain the factors responsible for the changes in atmospheric pressure on the earth’s surface.
Ans The atmospheric pressure varies from place to place and from time to time. The variations in atmospheric pressure is due to the
1) Temperature of the air
2) density of the air
3) height of a place above the sea level.
4) amount of moisture present in the air
Que 2 Describe the main features of planetary winds.
Ans Some winds blow constantly in a particular direction throughout the year. These winds are known as prevailing winds or permanent winds or planetary winds. These winds originate due to the presence of permanent high pressure and low pressure belts on the surface of the earth. The main types of planetary winds are the Trade winds, the Westerlies and the Polar winds
Que 3 How does the amount of moisture in the atmosphere vary from place to place and also from time to time?
Ans The amount of moisture present in the air varies from place to place and from time to time. The air in the equatorial region has more moisture than other regions of the world. The air has more moisture during the summer season than during the winter season. The amount of moisture decreases with the increase in height above the mean sea level. The amount of moisture is almost zero in the cold air of the polar regions during the winter months.
Que 4 Name and explain the various types of rainfall.
Ans The three types of rainfall are:
1) Convectional Rainfall – Air gets heated after coming in contact with earth and becomes lighter. It rises up and become cooler with increase in height, which leads to condensation and formation of cumulus clouds, these clouds cause rainfall with thunder and lightning. Such type of rainfall is experienced every near the equator.
2) Orographic rainfall – When the moist air ascend along the slop of any mountain, then it leads to condensation and formation of clouds and cause rainfall. Such type of rainfall is experienced in areas near the mountains.
3) Cyclonic Rainfall – Cyclones are formed in warm sea, the air present here creates low pressure and cold wind blow towards these areas, when cold and warm wind comes in contact the lighter warm wind rides the cold wind, which increase the height of the warm air and condensation takes place in the warm air and rainfall takes place in along the path of cyclone.
HOTS
Que 5 Why do you think the amount of insolation increases from the poles towards the equator?
Ans The amount of insolation increases from the poles towards the equator because in low latitudes the Sun’s rays are direct and have to travel a lesser extent through the atmosphere. Hence, the heat of these rays is more intense. But in higher latitudes, the Sun’s rays are slanting and have to pass through a greater extent of atmosphere. Hence, these rays lose heat on the way and minimum insolation occurs at the poles.
Que 6 Why does cold air exert more pressure than warm air?
Ans Cold air exerts more pressure that warm air because the molecules of cold air are huddled together closely making it denser where as in warm air, they are lighter and more dispersed. Denser air exerts more pressure compared to lighter air, hence cold air has more pressure.
Que 7 Why does the equatorial region experience permanent low pressure?
Ans Due to the spherical shape of the earth, different parts of the earth are heated unequally. The Equatorial region receives a great amount of heat throughout the year. Warm air being light rises up creating low pressure. Also the Sun’s rays strike the equator almost directly, leading to intense heating of the air near the surface. As pressure is inversely proportional to temperature, hence due to high temperatures in equatorial region, low pressure develops there.
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