# Current Affairs 4th Class

#### Safety and First Aid

Safety and First Aid   Synopsis
 Tit Bits We should pour water for minor or slight burns. If somebody catches fire, wrap them in a blanket, give the first aid and take him to the doctor immediately.

• Accidents mostly happen when we are careless. Accidents can be easily prevented by following rules of safety at home, school and public places.

• You have to be very careful with sharp knives, stoves, fire and with electrical appliances.

• In the bathroom use rubber mats or bathmats to prevent from slipping. Never touch an electric switch with wet hands.

• At school be careful while climbing staircase never climb on desks and chairs.

• At the playground never push or kick someone while playing a game. Never swim alone.

• First-Aid is the immediate help given to a sick or an injured person before proper medical help arrives.

• First-Aid can save a person's life. It can also prevent permanent injuries.
First-Aid Tips
• For cuts and wounds: Wash the wound or cut with water to remove dirt. Wipe with antiseptic lotion and put a Band-Aid to a minor cut and a deeper cut may need cotton pad and sterilised bandage.
• For burns: Wash the minor burnt area with running water and put an antiseptic cream.
• For insect bites: Apply calemine lotion, paste of baking soda with an antiseptic cream.
• If a person has fainted: Make him lie down with his head lower than the body.

#### Our Clothes

Our Clothes   Synopsis
 Tit Bits Linen is a fibre that is obtained from the stem of the flax plant.

• Clothes protect us from heat, cold and dust. Clothes are of different types and made in different ways.

• Silk clothes are made from saliva of an insect called silkworm. When the silkworm is in pupa stage it secretes saliva and builds cocoon around itself. These pupae are placed in boiling water and the worms inside are killed. Silk thread is weaved from the pupal case. The threads are then dyed and cloth is prepared.

• Woollen clothes are made in a similar manner except that the thread is prepared from the fleece of sheep. Woollen clothes keep us warm and are widely used in cold climates.

• Cotton clothes are made from cotton plants. Cotton seeds are separated from the cotton bolls and cotton is spun in the form of threads.

• Clothes are manufactured on a large scale in big factories.

• Naphthalene balls and dried leaves of neem keep insects away from the clothes.

• Nylon and terylene are synthetic fibres prepared from carbon compounds.

• We wear different clothes in different seasons. In warm and dry summer days cotton clothes are comfortable because they allow the body heat to escape, absorb heat and keep our body cool.

• In cold winter days we wear thick, warm clothes made of wool to keep our body warm.

• Raincoat and umbrella are useful in the rainy season.

• Socks and shoes protect our feet from heat, dust and cold and prevent germs from entering our body.

• Clothes should be properly rinsed in water and regularly washed. Cotton clothes are washed with soap and water. Silk and woolen clothes need dry cleaning.

#### Air, Water and Weather

Air, Water And Weather   Synopsis
 Tit Bits When water boils, the bubbles that are seen bursting on the water are not air bubbles. In fact, they consists of water vapour.

• Weather is the condition of the sun, air, water and clouds of a place at a particular time.

• Air is a mixture of gases like nitrogen, oxygen, carbon dioxide, water vapour etc.

• The percentage of oxygen and carbon dioxide is kept at a constant level by photosynthesis and respiration.

• We cannot see the air as it is invisible. But we can feel the presence of air. Air occupies space and exerts pressure.

• The sun plays an important role in causing changes in the weather.

• The noon is hottest time of a day because sun's rays fall directly over our head.

• Land and water are heated up differently by the sunlight. Land gets warmer faster than water during the day. Land also cools faster than water in the evening.

• During the day, land is hotter than the sea. So the air above the land gets warmer than the air over the sea. Hot air above the land being lighter, rises and the cool air from the sea takes its place. In this way air blows from sea towards the land. This is called sea breeze.

• At night, The sea is hotter than the land and cooler air above the land moves towards the sea, as the warmer air above the sea rises. Thus air starts to move from the land towards the sea. This is called land breeze.

• The change of water into water vapour is called evaporation. It also increases with the temperature and area of exposure to air. Evaporation is higher on a dry day.

• Change of water vapour into water is called condensation. When the temperature is cooled, water vapour turns to water.

• In the morning we can observe small drops of water on grass blades and leaves of more...

#### ­­­Our Universe

Our Universe   Synopsis
 Tit Bits From the earth, stars seem to twinkle because the light from the stars is affected by the different layers of wind in the blanket of air covering the earth.

• There are millions of stars in the sky.

• Some stars seem to form interesting shapes and patterns. They are called constellations. Constellations are usually given names based on the their shapes.
e.g., Orion constellation, Saptarshi or big bear constellation.
• The sun is also a star and it looks bigger because it is closer to us. All the other stars are very far away from the earth.

• Huge spheres which move around the sun in fixed paths are called planets. The path of a planet is called its orbit.

• Our sun and its planets together form solar system. The planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

• The following are some facts about the solar system:

Biggest planet                -  Jupiter
Nearest planet to the sun      - Mercury
Brightest planet              - Venus
Planets with rings             - Saturn
Planets without satellite       - Mercury, Venus
Beautiful planet              - Saturn
more...

#### Matter

Matter   Synopsis
 Tit Bits Gases are the substance in which the particles are very loosely packed and can compressed. Gases like LPG and CNG are compressed in cylinders and are used as fuels.

• Any substance that has weight and occupies space is called matter. Matter exists in three states: solids, liquid and gases.

• The molecules of solids are very closely packed with strong forces of attraction between them. They cannot move about freely.
Solids have fixed shapes and volumes.
• The molecules in the liquid are loosely packed with weak forces of attraction. They move about more freely than in solids. Liquids have fixed volume but no fixed shape. They take up the shape of the container in which they are poured.

• In gases the molecules are very loosely packed. They have very weak forces of attraction between them. Gases do not have fixed shape or volume. They occupy all the available space.

• The different states of matter are interchangeable. When solids are heated they become liquids. When liquids are heated they become gases. When gases are cooled they become liquids, which upon further cooling become solids.
$Solids\underset{cool}{\overset{heat}{\longleftrightarrow}}Liquids\underset{cool}{\overset{heat}{\longleftrightarrow}}Gases$
• Solids dissolve in liquids. The substances which dissolve in a liquid are called soluble and those which do not, are called insoluble.

• The substance which dissolves is called a solute. The substance in which the solute dissolves is called solvent. The combination of solute and solvent is called solution.
For example, when sugar dissolves in water it forms sugar solution. The solute is sugar and the solvent is water and the solution is sugar solution.
• When things dissolve, the solute particles occupy the small spaces present between the molecules of the solvent. Even some gases like oxygen and carbon dioxide dissolve in water.

• Undissolved substances can be separated from the solvent through filtration.

• Dissolved substances can be separated by evaporation. When a solution is heated, the solvent evaporates and the solute is left behind. Common salt is obtained by the evaporation of sea water.
more...

#### Force, Work and Energy

Force, Work and Energy   Synopsis
 Tit Bits Renewable sources of energy are those that are renewed naturally. For example, solar energy, wind energy and water energy.

• Force is the push or pull of an object.

• By applying force, we can
-move a body, -stop a moving body, -change the direction of a moving body and -make the body move slower or faster.
• Friction is the force which stops the movement of a body when the body is in contact with a surface.

• Force moves objects and friction stops objects.

• There are different types of forces. Animals and human beings use muscular force.

• The force applied with the help of tools is called mechanical force and it produces movement.

• The force of the earth on all the bodies present on it is called gravitational force.

• When a force moves an object through a distance, then work is said to be done.

• The tools which help us in doing work are called simple machines.
e.g., scissors, pulley, etc.
• Machines increase the speed of work being done and change the direction of force.

• Energy is the capacity to do work.

• The energy stored in our muscles is called muscular energy.

• A moving wind has energy. It is used to produce electricity.

• The energy possessed by moving water is called hydel energy or water energy.

• The electricity produced with hydel energy is called hydroelectricity.

• Burning of fuels produces heat energy. It is used to cook food, heating water and to run vehicles.

• Electrical energy is used to produce light and run different machines.

• The energy we get from the sun is called solar energy.

• Energy can be converted from one form to another.

• The sun is the ultimate source of energy.
more...

#### Large Numbers

Large Numbers   Synopsis
• The ten digits in the number system are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.
• 0 is the smallest 1 - digit number and 9 is the largest 1 -digit number.

 No. of digits Smallest Counting Number Largest Counting Number 1 1 9 2 10 99 3 100 999 4 1000 9999 5 10000 99999 6 100000 999999
Place Value Chart:
 Lakshs Period Thoudands periods Ones period Ten lakhs Lakhs Ten Thousands Thousands Hundreds Tens Ones

 10 ones =  1 ten 10 tens = 1 hundred 10 hundreds = 1 thousands 10 thousands = 1 ten thousands 10  ten thousands = 1 lakh 10 lakhs = 1 ten lakh

 1000 ones = 1 hundred 100 tens = 1 thousand 100 thousands = 1 lakh

• While writing large numbers, the digits of each period are separated using a comma.
• g., 694537 is written as 6, 94, 537.

 Lakhs period Thousand period Ones period TL L T. Th Th H T O 6 9 4 5 3 7

• Place value of a digit is the product of the digit and its place. (Position in the more...

#### Roman Numerals

Roman Numerals   Synopsis          Rules for writing Roman Numerals:   (a) If a smaller numeral is written after a larger numeral, their values are added. e.g.,     (b) If a smaller numeral is written before a larger numeral, its value is subtracted from that of the larger numeral. e.g.,   (c) Repetition of a numeral means addition.   Note: A Roman numeral can be repeated can be repeated to a maximum of three times.   e.g.,   (d) If a smaller numeral is placed between two larger numerals, the value of the smaller numeral is subtracted from the value of the larger numeral following it. e.g.,  (and not)   Remember: (a) V is never repeated. (b) V can never be subtracted from X. (c) I can be subtracted only from V and X.

• When two numbers are added, each of them is called an addend and the answer obtained is called the sum.
e.g.,
• Two numbers added in any order give the same sum.
e.g., 4126+3143 =7269 Also, 3143+4126 =7269
• When one of the addends is 0, the sum is the addend other than 0.
e.g., 6740 + 0 = 6740 In other words, when zero (0) is added to any number, the sum obtained is the number itself.
• When two numbers are added (none of them is zero), their sum is greater than each of the numbers.
e.g., 5365 + 2234 = 7599 7599 > 5365 and 7599 > 2234   Addition (Using estimation):   e.g., Add 3451 and 6215. The addends can be estimated to the nearest 1000 or 100.   (a) Estimating to the nearest 1000:
• rounds to 3000.
• 6215 rounds to 6000.
So, 3000+6000 =9000 Actual sum = 3451 + 6215 = 9666   (b) Estimating to the nearest 100:   3451 rounds to 3500. 9700 is closer to the actual sum i.e., 9666 than 9000. So, rounding a 4-digit addend to the nearest 100 gives a better estimate of the sum.
• Subtraction:
•
• The answer obtained when two numbers are subtracted is called difference. The number which is subtracted is called the subtrahend and the number from which another number is subtracted is called the minuend.
e.g.,
 62135 - 30014 = 32121 Minuend Subtrahend Difference
Properties of subtraction:   (a) While subtracting, the order in which numbers are taken is important. e.g., 4261 - 3417 is not the same as 3417 - 4261.   Note: Only smaller number can be subtracted from the larger ones.   (b) When '0' is subtracted from a number/the difference is the number itself. (c) On adding the difference and the subtrahend, we get the minuend. (d) The difference of two numbers is always lesser than the minuend. (e) When a number is subtracted from itself, the difference is zero.   Subtraction (using estimation):   e.g., Subtract 3451 from 6215. The subtrahend and the minuend can be estimated to the nearest 1000 or 100.   (a) Estimating to the more...

#### Multiplications and Division

Multiplications and Division   Synopsis
• Multiplication:
• Multiplication is repeated addition of the same number.
e.g., $\text{15}+\text{ 15 }+\text{ 15 }+\text{ 15 }=\text{ 4}\times \text{15}$
• In a multiplication, the number that is multiplied is called multiplicand, the number by which it is multiplied is called multiplier and the answer obtained is called result or

 e.g.,
Properties of multiplication:   (a) Changing the order of numbers to be multiplied does not change their product. e.g., $\text{5}\times \text{9}=\text{ 45 }=\text{9}\times \text{5}$ (b) The product of any number and 0 is 0. e.g., $~\text{43}\times 0=0$ (c) The product of any number and 1 is the number itself. e.g., $~\text{59}\times \text{1}=\text{59}$ (d) The product of a number and the sum of two numbers is equal to the sum of the products with the two numbers separately. e.g., $\text{4}\times (\text{3 }+\text{ 6})=\text{4}\times \text{9}=\text{36}$ $\therefore$ $\text{4}\times (\text{3}+\text{6})=\text{4 }\times \text{ 3}+\text{4 }\times \text{ 6}=\text{12}+\text{24}=\text{36}$ (e)  To multiply a number by $\text{1}0,\text{ 2}0,\text{ }.....\text{ 9}0,$ first multiply the number by $\text{1},\text{ 2},\text{ }...\text{ 9}$respectively and place a zero to the right of the product. e.g., $\text{146 }\times \text{ 2}0=\text{146 }\times \text{ 2 }\times \text{ 1}0=\text{292 }\times \text{ 1}0=\text{292}0$(f) To multiply a number by $\text{1}00,\text{2}00,\text{3}00,\text{ }....,\text{9}00,$ first multiply the number with $\text{1},\text{2},\text{3},\text{ }....,\text{9}$and place two zeroes to the right of the product. e.g., \[~\text{456 }\times \text{ 1}00\text{ }=\text{ 456 }\times \text{ 1 }\times more...

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