Prasanna

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CBSE Class 8 Maths Chapter 7 Notes Cubes and Cube Roots

Cubes and Cube Roots Class 8 Notes Conceptual Facts

• A natural number n is a perfect cube if there exists a natural number m such that m x m x m = n For example: 1, 8, 27 …. are all perfect cubes

Properties of Cubes of Numbers:

• Cubes of all odd numbers are odd. Thus 3³ = 27, 5³ = 125, etc.
• Cubes of all even numbers are even. Thus 2³ = 8, 4³ = 64, 6³ = 216, etc.
• Cubes of all negative numbers are always negative. Thus (-1)³ = -1, (-2)³ = -8, (-3)³ = -27, etc.
• \(\left(\frac{a}{b}\right)^{3}=\frac{a^{3}}{b^{3}}\)

Properties of Cube Roots:

(i) \(\sqrt[3]{-a^{3}}=-a\)

(ii) \(\sqrt[3]{a b}=\sqrt[3] a^{a} \sqrt[3]{b}\)

(iii) \(\sqrt[3]{\frac{a}{b}}=\frac{\sqrt[3]{a}}{\sqrt[3]{b}}, b \neq 0\)

A Pattern of Cube:

1³ = 1
2² = 8 = 3 + 5
3³ = 27 = 7 + 9 + 11
4³ = 64 = 13 + 15 + 17 + 19
5³ = 125 = 21 + 23 + 25 + 27 + 29

 

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CBSE Class 8 Maths Chapter 6 Notes Squares and Square Roots

Squares and Square Roots Class 8 Notes Conceptual Facts

1. If a number is multiplied by itself, the product that we get is called the square of the number.
For example:
4 x 4 = 4² = 16                                                                 (16 is square of 4)
20 x 20 = 20² = 400                                                         (400 is square of 20)
\(\frac{3}{5} \times \frac{3}{5}=\left(\frac{3}{5}\right)^{2}=\frac{9}{25}\) \(\left(\frac{9}{25} \text { is square of } \frac{3}{5}\right)\)

2. Square of a number is represented as the number raised to the power 2.

3. A perfect square is a number that can be expressed as the product of two equal integers.
For example: 1, 4, 9, 16, 25, …, are all perfect square numbers.

4. Properties of square numbers:
(i) No square number ends with the digits 2, 3, 7 or 8 at its unit places.

(ii) The square numbers must end with the digits 0, 1, 4, 5, 6, 9 but the number ending with 0, 1, 4, 5, 6, 9 may or may not be a perfect number.
For example: 36 is a perfect square but 56 is not.
256 is a perfect square but 346 is not.

(iii) Square of even number is always an even and the square of odd number is odd.
For example:
4² = 16(even)
5² = 25(odd)

(iv) A perfect square can never be a negative number.

(v) For every natural number n, (n + 1)² – n² – (n + 1) + n
For example: 14² -13² = (13 + 1) + 13 = 14 + 13 = 27
26² – 25² = (25 + 1) + 25 = 26 + 25 = 51

5. Pythagorean Tripletr: A triplet (m, n,p) is called a Pythagorean triplet if m² + n² = p²
For example: (3, 4, 5), (8, 15, 17) and (20, 21, 29)
Product of two consecutive even or odd natural numbers:
Example:
11 x 13 = 143 – 12² – 1 (product of odds)
13 x 15 = 195 = 14² – 1 (product of odds)
44 x 46 = 2024 = 45² – 1 (product of evens)

Some Patterns in square numbers:

 

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CBSE Class 8 Maths Chapter 5 Notes Data Handling

Data Handling Class 8 Notes Conceptual Facts

1. Data: Collection of information as numerical facts about the objects or events is called Data.

2. Types of Data: Discrete and continuous.

3. Frequency: The number of times each score occurs is called frequency.

4. Range: The difference between the greatest and the least observations is called the Range.

5. Relative Frequency: The ratio of the frequency of each item to the sum of all frequencies is called Relative frequency.
\(\text { Relative frequency }=\frac{\text { Frequency of an object }}{\text { Total frequency }}\)

6. Class-size: Difference between upper and lower limits of a class interval is called class-size.

7. Class-mark: Mid value of class interval is called its class-mark.
\(\text { Class-mark }=\frac{\text { Upper limit }+\text { Lower limit }}{2}\)

8. Class-frequency: The frequency of a particular class-interval is called class-frequency.

9. Bar Graph: Horizontal and vertical Histogram: Horizontal and vertical

10. Pie chart: Pie chart is a way of representing the data in the form of sectors of a circle.
Central angle for a sector = \(\left(\frac{\text { Value of the component }}{\text { Total value }} \times 360\right)^{\circ}\)

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Drainage Class 9 Notes Social Science Geography Chapter 3

CBSE Class 9 Geography Chapter 3 Notes Understanding the Lesson

1. The term ‘Drainage’ describes the river system of an area. The area drained by a single river system is called a drainage basin.

2. Any mountain or an upland separating two drainage basins is called a water divide.

3. The Indian rivers are divided into two major groups

• the Himalayan rivers and
• The peninsular rivers.

4. Some of the features of the Himalayan rivers are-they are perennial, they have long courses from heir source to the sea, they perform intensive erosional activity in their upper courses and carry huge loads of silt and sand.

5. Some of the features of the Peninsular rivers are-they are seasonal, they have shorter and shallower courses as compared to the Himalayan rivers, most of them originate in the Western Ghats and flow towards the Bay of Bengal.

6. The streams within a drainage basin form certain patterns, depending on the slope of land, underlying rock structure as well as the climatic conditions of the area.

7. Types of drainage patterns are-dendrite, trellis, rectangular and radial patterns.

8. The major Himalayan rivers are-the Indus, the Ganga and the Brahmaputra. The river Indus rises in Tibet, near Lake Mansarovar. It flows through Baltistan and Gilgit and emerges from the mountains at Attock. The Indus plain has a very gentle slope. The Indus is one of the longest rivers of the world.

9. The Ganga emerges from the mountains on to the plains at Haridwar. The river is joined by tributaries such as the Yamuna, the Ghaghara, the Gandak and the Kosi. The length of the Ganga is over 2500 km.

10. The Brahmaputra is slightly longer than the Indus and most of its course lies outside India. The river rises in Tibet east of Mansarovar lake. It flows eastwards parallel to the Himalayas. Every year during the rainy season, the river overflows its banks, causing widespread devastation due to floods in Assam and Bangladesh.

11. Major rivers of the Peninsula such as the Mahanadi, the Godavari, the Krishna and the Kaveri flow eastwards and drain into the Bay of Bengal. These rivers make deltas at their mouths. The Narmada and the Tapi flow west and make estuaries.

12. The Narmada rises in the Amarkantak hills in the Madhya Pradesh. On its way to the sea, it creates many picturesque sites. The Narmada basin covers parts of Madhya Pradesh and Gujarat.

13. The Tapi rises in the Satpura ranges, in the Betul district of Madhya Pradesh. Its basin covers parts of Madhya Pradesh, Gujarat and Maharashtra.

14. The Godavari, the largest Peninsular river, rises in the Nasik district of Maharashtra. Its basin covers parts of Maharashtra, Madhya Pradesh, Odisha and Andhra Pradesh.

15. The Mahanadi rises in the highlands of Chhattisgarh. Its drainage basin is shared by Maharashtra, Chhattisgarh, Jharkhand and Odisha.

16. The Krishna rises from a spring near Mahabaleshwar. It drains into the Bay of Bengal. Its drainage basin is shared by Maharashtra, Karnataka and Andhra Pradesh.

17. The Kaveri rises in the Brahmagri range of the Western Ghats and it reaches the Bay of Bengal in south of Cuddalore, in Tamil Nadu. Its basin drains parts of Karnataka, Kerala and Tamil Nadu.

18. India has many lakes which differ from each other in size, and other characteristics. Most lakes are permanent while some contain water only during the rainy season.

19. Some of the lakes have come into existence as the result of the action of glaciers and ice sheets while the others have been formed by wind, river action and human activities.

20. Most of the fresh-water lakes are in the Himalayan region. The Wular lake in Jammu and Kashmir is the largest freshwater lake in India. Some lakes such as Guru Gobind Sagar have been artificially created by damming of rivers for power generation.

21. Rivers play an important role in country’s economy. Their water is used for irrigation, navigation, hydro-power generation, etc.

22. Excess use of river water has affected its quality. Untreated sewage and industrial effluents are emptied into the rivers as a result of which their self-cleansing capacity is lost.

23. Increasing urbanization and industrialization are also major reasons of river pollution. It is high time to think over it and do accordingly.

Drainage Class 9 CBSE Notes Important Terms

Drainage: The river system of an area.

Drainage basin: The area drained by a single river system.

Water divide: Any mountain or an upland that separates two drainage basins is called a water divide.

Perennial rivers: Rivers having water throughout the year.

River system: A river along with its tributaries.

Seasonal rivers: Rivers having water only during rainy season.

Floodplain: An area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.

River delta: A landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water.

Gorges: Deep, narrow valleys with a stream or river running along their bottom.

Bhagirathi: The headwaters of the Ganga.

Tributary: A river or stream flowing into a larger river or lake.

Glacier: A slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles.

Distributary: A branch of a river that does not return to the mainstream after leaving it as in a delta.

Meander: A winding curve or bend in a river.

Rift valley: A linear-shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault.

Lake: A large area of water surrounded by land.

Sea: A lake of large extent.

Trough: A narrow depression as in the earth or between ocean waves or in the ocean bed. A narrow channel, gutter or gulley.

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CBSE Class 8 Maths Chapter 4 Notes Practical Geometry

Practical Geometry Class 8 Notes Conceptual Facts

Construction of four-sided figures when

• Four sides and one diagonal are given.
• Two diagonals and three sides are given.
• Two adjacent sides and three angles are given.
• Three sides and two included angles are given.

Some special cases:

• To construct a square when only one side is given.
• To construct a trapezium.

Quadrilaterals basically has ten parts in all, four sides, four angles and two diagonals.

To construct a quadrilateral, we need the measurement of five specified parts.

Before constructing a figure, we need to draw a rough free hand sketch.

Using the properties of the quadrilateral, we can construct parallelograms, squares, rectangles, rhombuses and trapeziums.

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CBSE Class 8 Maths Chapter 3 Notes Understanding Quadrilaterals

Understanding Quadrilaterals Class 8 Notes Conceptual Facts

Polygon: A simple closed curve made up of only line segments is called a polygon.
Examples of Polygons:
(i) Triangle

(ii) Quadrilateral

(iii) Pentagon

(iv) Hexagon

Convex and concave polygons

Regular and irregular polygons

Angle sum property: The sum of three angles of a triangle is 180° In AABC, ∠A + ∠B + ∠C = 180°

Sum of all the exterior angles of a polygon is 360°. In the given polygon ABODE, exterior angles ∠1 + ∠2 + ∠3 + ∠4 + ∠5 = 360°.

Kind of Quadrilaterals

(i) Parallelogram

Properties
(a) Opposite angles are equal
(b) Opposite sides are equal
(c) Diagonals bisect each other

(ii) Rhombus:

(a) All sides are equal
(b) Opposite angles are equal
(c) Diagonals bisect each other at 90°

(iii) Rectangle

(a) It is a parallelogram having each angle of 90°
(b) Opposite sides are equal
(c) Diagonals are equal

(iv) Square:

(a) All sides are equal
(b) Each angle is of 90°
(c) Diagonals are equal and bisect each other at 90°

(v) Kite:

(a) Diagonals are perpendicular to each other.
(b) One of the diagonals bisects the other
(c) m∠A = m∠C but m∠B ≠ m∠D

(vi) Trapezium:

A pair of opposite sides is parallel to each other.

On this page, you will find NCERT Class 9 Geography Chapter 1 Notes Pdf free download. CBSE Class 9 Social Science Notes Geography Chapter 1 SST India Size and Location will seemingly, help them to revise the important concepts in less time. India Size and Location

India Size and Location Class 9 Notes Social Science Geography Chapter 1

CBSE Class 9 Geography Chapter 1 Notes Understanding the Lesson

1. India lies entirely in the Northern Hemisphere. The mainland extends between latitudes 8°4′ N and 37°6′ N and longitudes 68°7′ E and 97°25′ E. The Tropic of Cancer divides the country in two halves. The landmass of India has an area of 3.28 million square km. India’s total area accounts for about 2.4 percent of the total geographical area of the world.

2.India has a land boundary of about 15,200 km and the total length of the coastline of the mainland including Andaman and Nicobar and Lakshadweep is 7,516.65 km.

3. The Indian landmass has a central location between the East and West Asia. India is a southward extension of the Asian continent.

4. India occupies an important strategic position in South Asia. India has 29 states and 7 Union Territories. The neighbouring countries of India are-Pakistan, Afghanistan, China, Nepal, Bhutan, Myanmar, Bangladesh, Sri Lanka and Maldives.

5. India has had strong geographical and historical links with her neighbours.

India Size and Location Class 9 CBSE Notes Important Terms

Longitude: It refers to the imaginary lines that bisect the globe through the North and South Poles the ones that run vertically, as opposed to the lines of latitude that run horizontally, parallel to the equator.

Latitude: The angular distance east or west on the earth’s surface, measured by the angle contained between the meridian of a particular place and some prime meridian, as that of Greenwich, England, and usually expressed in degrees.

Equator: The imaginary great circle around the earth’s surface equidistant from the poles and perpendicular to the earth’s axis of rotation. It divides the earth into the Northern Hemisphere and the Southern Hemisphere.

Mainland: A large continuous extent of land that includes the greater part of a country or territory, as opposed to offshore islands and detached territories.

Coastline: The land along a coast. A line that forms the boundary between the land and the ocean, or a lake.

Pass: A gap or break in high, rugged terrain such as a mountain ridge.

Merchandise: Goods to be bought and sold.

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CBSE Class 8 Maths Chapter 2 Notes Linear Equations in One Variable

Linear Equations in One Variable Class 8 Notes Conceptual Facts

1. Statement of equality containing one or more variable (unknown quantity) is called an equation.
For example: 3x – 5 = 6, x – 3y = 7, \(\frac{x}{2}+\frac{y}{3}=5\) , x² + 5 = y² are all equations.

2. Linear equations of one variable contains only one variable.
For example: \(3 x-1=\frac{1}{2}, 5-x=\frac{3}{2}, \frac{6 x}{5}-3=0\)

3. The value of the variable which makes an equation true is called the solution of the equation.
x² + y² = 7 type equations are not linear equations.
(i) Rules for solving an equation.

• Same number can be added to both sides of equality sign (=).
• Same number can be subtracted from both the sides of equality sign (=).
• Same number can be multiplied to both the sides of equality sign (=).
• Both sides of the equation can be divided by the same number.

For example:
3x – 4 = 7
⇒ 3x- 4 + 4- 7+ 4 (adding 4 to both sides)
⇒ 3x = 11
⇒ 3x÷3 = 11÷3 (dividing the both sides by 3)
\(x=\frac{11}{3}\)
Thus, \(x=\frac{11}{3}\) is the solution or root of the equation.

(ii) Rule of transpositions: Any term can be transposed from one side of the equation to the other side by changing its sign, i.e. (+) to (-), (-) to (+), (x) to (-r) and (v) to (x).

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Physical Features of India Class 9 Notes Social Science Geography Chapter 2

CBSE Class 9 Geography Chapter 2 Notes Understanding the Lesson

1. The land of India displays great physical variation. Different geological periods have influenced her relief. Besides geographical formations, a number of processes such as weathering, erosion and disposition have created and modified the relief to its present form.

2. According to the theory of Plate tectonics, the upper part of the earth has been formed out of seven major and some minor plates. The movement of these plates are classified into three types- convergent boundary, divergent boundary and transform boundary.

3. The oldest landmass was a part of the Gondwana land. The Gondwana land included India, Australia, South Africa, South America and Antarctica as one single landmass.

4. Geologically, the Peninsular Plateau constitutes one of the ancient landmasses on the earth’s surface. The Himalayas and the Northern Plains are the most recent landforms.

5. The physical features of India can be grouped under six physiographic divisions-the Himalayan Mountains, the Northern Plains, the Peninsular Plateau, the Indian Desert, the Coasted Plains and the Islands.

6. The whole mountain system of Himalayas represents a very youthful topography with high peaks, deep valleys and fast-flowing rivers. The Himalayas consist of three parallel ranges in its longitudinal extent-The Great or Inner Himalayas or the Himadri, Himachal or lesser Himalayas and the Shivaliks.

7. Besides the longitudinal divisions, the Himalayas have been divided on the basis of regions from west to east-Punjab Himalayas, Kumaon Himalayas, the Nepal Himalayas and Assam Himalayas.

8. The Brahmaputra marks the easternmost boundary of the Himalayas known as the Purvachal or the eastern hills and mountains. The Purvachal comprises the Patkai hills and Naga hills, Manipur hills and the Mizo hills.

9. The Northern Plains are formed of alluvial deposits. The three major river systems of which the plain have been formed are-the Indus, the Ganga, and the Brahmaputra along with their tributaries.

10. The Northern plains are broadly divided into three sections-The Punjab plains, the Ganga plain and the Brahmaputra plain. These plains have diverse relief features. According to the variations in relief features, they can be divided into four regions.

11. The largest part of the Northern Plains is formed of older alluvium. They lie above the floodplains of the rivers and is known as The newer, younger deposits of the flood plains are called khadar.

12. The Peninsular plateau is composed of igneous and metamorphic rocks with gently rising hills and wide valleys. This plateau consists of two broad divisions, namely, the Central Highlands and the Deccan Plateau. The Deccan Plateau is a triangular landmass that lies to the south of the river Narmada.

13. The Western Ghats and the Eastern Ghats mark the western and the eastern edges of the Deccan plateau respectively. The Western Ghats are continuous and are higher than the Eastern Ghats.

14. The Great Indian desert lies towards the western margins of the Aravali Hills. It is an undulating sandy plain covered with sand dunes. This region receives very low rainfall.

15. The coastal plains of India are located along the Arabian Sea coast in the west and along the Bay of Bengal coast in the east. According to their location to the east or west of the peninsular plateau, they are a called-East coastal plain and West coastal plain.

16. India has two groups of Islands-The Lakshadweep Islands groups and the Andaman and Nicobar Islands. The Lakshadweep Islands groups lie close to the Malabar coast of Kerala and the Andaman and Nicobar Islands are located in the Bay of Bengal.

17. Different physiographic units highlights the unique features of each region. Each region complements the other and makes the country richer in its natural resources.

Physical Features of India Class 9 CBSE Notes Important Terms

Folding: A type of earth movement resulting from the horizontal compression of rock layers by internal forces of the earth along plate boundaries.

Faulting: A crack in the earth’s crust resulting from the displacement of one side with respect to the other.

Gondwana land: It is the southern part of the ancient supercontinent Pangea with Angara land in the northern part.

Tethys: The sedimentary rocks accumulated in the geosyncline.

Duns: The longitudinal valley lying between lesser Himalaya and the Shivaliks.

Alluvium: A deposit of clay, silt and sand left by flowing floodwater in a river valley or delta, typically producing fertile soil.

Doab: The term is made up of two words-‘do’ meaning two and ‘ab’ meaning water.

Distributaries: Branches of rivers that do not return to the mainstream after leaving it.

Terai: A wet, swampy and marshy region.

Kankar: The soil containing calcareous deposits.

Khadar: The newer, younger alluvium of the flood plains.

Bhangar: The older alluvium lying above the flood plains of the rivers and presenting a terrace like feature.

Central Highlands: The part of the Peninsular plateau lying to the north of the Narmada river covering a major area of the Malwa plateau.

Western Ghats: The western edges of the Deccan plateau.

Eastern Ghats: The eastern edges of the Deccan plateau.

Deccan Trap: The black soil area of the Peninsular plateau.

Barchans: Crescent-shaped dunes found in the desert regions.

Dune: A hill of loose sand built by wind or the flow of water.

Konkan: The northern part of the coast.

Kannad plain: The central stretch of level open land.

Coral polyps: Short-lived microscopic organisms, which live in colonies.

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CBSE Class 8 Maths Chapter 1 Notes Rational Numbers

Rational Numbers Class 8 Notes Conceptual Facts

1. A number which is in the form of \(\frac{p}{q}\), where p and q are co-primes integers and q ≠ 0 is called rational number.
For example, \(\frac{2}{3}, \frac{1}{2}, \frac{4}{5}, 2,-\frac{6}{7}\)

2. Every fraction is a rational number but every rational number need not to be a fraction.
For example: \(\frac{2}{3}\) is a fraction as well as a rational number, o
Whereas -5 is a rational number but it is not a fraction.

3. Standard form of a rational number may be identified when its denominator is positive.
For example: Standard form of is \(\frac{18}{-24} \text { is } \frac{-3}{4}\)

4. Equivalent fraction of \(\frac{p}{q}\) may be denoted by \(\frac{p \times m}{q \times m} \text { or } \frac{p \div n}{q \div n}\)
For example: Equivalent fractions of  \(\frac{12}{16} \text { are } \frac{12+4}{16 \div 4}=\frac{3}{4}\)
or \(\frac{12 \times 2}{16 \times 2}=\frac{24}{32}\)

5. The rational numbers can be compared as:

• \(\frac{a}{b}>\frac{c}{d}\) if and only if ad > bc
• \(\frac{a}{b}=\frac{c}{d}\) if and only if ad = bc
• \(\frac{a}{b}<\frac{c}{d}\) if and only if ad < bc

Properties of rational numbers:
(а) Closure property additions
If a and b are two rational numbers, then a + b will also a rational number
For example: \(\frac{1}{2}+\frac{1}{3}=\frac{1 \times 3+1 \times 2}{6}=\frac{5}{6}\) a rational number.

(b) Commutative property of addition
Two rational numbers can be added in any manner.

(c) Associative property for addition:
While adding three or more rational numbers, they can be grouped in any order.

(d) Additive identity: The sum of any rational number and 0 is always equal to the rational number itself.
Zero is additive identity
For example: 0 + a = a or a + 0 = a

(e) Additive inverse
Additive inverse of \(\frac{a}{b}=-\frac{a}{b}\)
0 is the additive inverse of itself.

Properties of multiplication of rational numbers.
(a) Closure property: The product of two rational number is always a rational number.
For example: Take two rational numbers \(\frac{1}{2} \text { and } \frac{1}{3}\)
∴ \(\frac{1}{2} \times \frac{1}{3}=\frac{1}{6}\) which is also a rational numbers.

(b) Commutative property: The two rational numbers can be multiplied in any order,
i.e. a x b =b x a

(c) Associative property: Three or more rational numbers can be multiplied by grouping in different order,
i.e. (a x b) x c = a x (b x c)

(d) Multiplicative identity: If \(\frac{a}{b}\) is a rational number, then \(\frac{a}{b} \times 1=1 \times \frac{a}{b}=\frac{a}{b}\)
For example: \(\frac{2}{3} \times 1=1 \times \frac{2}{3}=\frac{2}{3}\)
1 is called the multiplicative identity of a rational number.

(e) Distributive property of multiplication over addition.
If \(\frac{a}{b}, \frac{c}{d} \text { and } \frac{e}{f}\) are three rational number,
For example:

For example: Let us consider three rational numbers \(\frac{2}{3}, \frac{4}{5} \text { and } \frac{5}{6}\)

Existence of multiplicative inverse (i.e. Reciprocal)
For every non-zero rational number \(\frac{a}{b}\), there exists its multiplicative inverse \(\frac{a}{b}\).

• i.e… \(\frac{a}{b} \times \frac{b}{a}=1\)
• Reciprocal of zero (0) is not defined.
• 1 and -1 are the only two rational numbers which are Reciprocal of their own.
• Reciprocal of a reciprocal of a number is the number itself.

Representation of rational numbers on number line.

Here A represents \(\frac{1}{3}\) and B represents \(\frac{-2}{3}\) on the given number line.

Rational numbers between two given rational numbers:

Let us consider the rational numbers \(\frac{3}{10} \text { and } \frac{7}{10}\)

So, the rational numbers between \(\frac{3}{10} \text { and } \frac{7}{10} \text { may be } \frac{4}{10}, \frac{5}{10} \text { and } \frac{6}{10}\)

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CBSE Class 10 Science Chapter 13 Notes Magnetic Effects of Electric Current

Magnetic Effects of Electric Current Class 10 Notes Understanding the Lesson

When an electric current is passed through a conductor, a magnetic field is produced around it.

1. Magnetic field

• The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field.
• Magnetic field is a quantity that has both direction and magnitude.
• The direction of the magnetic field is taken to be the direction in which a north pole of the compass needle moves inside it.

2. Magnetic field lines

• Magnetic field lines- are the imaginary lines along which the iron filings align themselves.
• By convention, the field lines emerge from the north pole and merge at the south pole. Inside the magnet, the direction of field lines is from the south pole to the north pole.

Properties of Magnetic field line

• Magnetic field lines are closed curves.
• The relative strength of the magnetic field is shown by the degree of closeness of the field lines.
• No two field lines can cross each other as at the point of intersection the compass needle would point towards two directions, which is not possible.

3. Magnetic field due to current carrying conductor

• The magnetic field around a current carrying conductors forms a pattern of concentric circles.
• The magnitude of the magnetic field produced at a given point increases as the current through the wire increases.
• The magnetic field produced by a given current decreases as the distance from it increases.

4. Right-hand thumb rule: The direction of magnetic field produced by a current carrying conductor can be found out by using the right-hand thumb rule.

Imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field, as shown in Figure. This is known as the right hand thumb rule.

(a) A pattern of concentric circles indicating the field lines of a magnetic field around a straight conducting wire. The arrows in the circles show the direction of the field lines. (b) A close up of the pattern obtained.

5. Magnetic field due to current-carrying circular loop

• At the centre of a current-carrying loop, the magnetic field appears to be a straight in line.
• The magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it.

6. Magnetic field due to a solenoid
Solenoid: A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid.

• The pattern of the magnetic field around a current-carrying solenoid is same as that of the bar magnet. One end of the solenoid behaves as a magnetic north pole, while the other behaves as south pole.
• The field lines inside the solenoid are in the form of parallel straight lines.
• The field is uniform inside the solenoid.
• A strong magnetic field produced inside a solenoid can be used to magnetise a piece of magnetic material, like soft iron, when placed inside the coil. The magnet so formed is called an electromagnet.
  

7. Force on a current-carrying conductor in a magnetic field

• A current carrying conductor when placed in a magnetic field experiences a force.
• If the direction of the field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both and will be given by Fleming’s left hand rule.
• Fleming’s left-hand rule: According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the forefinger points in the direction of magnetic field and the middle finger in the direction of current, then the thumb will point in the direction of the force acting on the conductor.

8. Electric motor: An electric motor is a rotating device that converts electrical energy to mechanical energy.
Principle: A current carrying conductor when placed in a magnetic field experiences a force.
Commercial motors are made up of:

• an electromagnet in the place of permanent magnet.
• large number of turns of the conducting wire in the current carrying coil.
• a soft iron core on which the coil is wound.

Electromagnetic induction: The phenomenon of electromagnetic induction is the production of induced current in a coil placed in a region where the magnetic field changes with time.

• The magnetic field may change due to relative motion between the coil and the magnet.
  
• If the coil is placed near a current carrying conductor, the magnetic field may change either due to a change in the current through the conductor or due to the relative motion between the coil and conductor.
• 

Fleming’s right-hand rule to know the direction of the induced current. Stretch the thumb, forefinger and middle finger of the right hand so that they are perpendicular to each other, as shown in the figure. If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of the conductor, then the middle finger will show the direction of induced current. This simple rule is called Fleming’s right-hand rule.

Fleming’s right-hand rule.
A galvanometer is an instrument that can detect the presence of a current in a circuit. The pointer remains at zero (the centre of the scale) for zero current flowing through it. It can deflect either to the left or to the right of the zero mark depending on the direction of current.
The induced current is found to be the highest when the direction of motion of the coil is at right angles to the magnetic field.

Electric Generator: A generator converts mechanical energy into electrical energy.

Principle: It works on the principle of electromagnetic induction.
AC generator produces AC current and DC generator produces DC current.

9. AC and DC

• The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically.
• In India, the AC changes direction after every 1/100 second, that is, the frequency of AC is 50 Hz.
• An important advantage of AC over DC is that electric power can be transmitted over long distances without much loss of energy.

10. Domestic Electric circuits

• In our houses we receive AC electric power of 220 V with a frequency of 50 Hz. One of the wires in this supply is with red insulation, called live wire. The other one is of black insulation, which is a neutral wire. The potential difference between the two is 220 V. The third is the earth wire that has green insulation and this is connected to a metallic body deep inside the earth. It is used as a safety measure to ensure that any leakage of current to a metallic body does not give any severe shock to a user.
• Fuse is the most important safety device, used for protecting the circuits due to short-circuiting or overloading of the circuits.

Class 10 Science Chapter 13 Notes Important Terms

Magnetic field: The area around a magnet in which its magnetic force can be experienced.

Right-Hand Thumb Rule: Imagine that you are holding a current carrying straight conductor in your right hand such that the thumb is pointing towards the direction of current. Then the fingers wrapped around the conductor will give the direction of the magnetic field.

Solenoid: A coil of many circular turns of insulated copper wire wrapped closely in a cylindrical form.

Electromagnet: An electomagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off.

Felming’s Left-Hand Rule: Stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the forefinger points in the direction of magnetic field, the middle finger in the direction of current then the thumb will point in the direction of motion or force.

Electromagnetic Induction: When a conductor is placed in a changing magnetic field, some current is induced in it. Such current is called induced current and the phenomenon is called electromagnetic induction.

Fleming’s Right-Hand Rule: Hold the thumb, the forefinger and the middle finger of right hand at right angles to each other. If the forefinger is in the direction of magnetic field and the thumb points in the direction of motion of the conductor, then the direction of induced current is indicated by the middle finger.

Electric motor: An electric motor is a rotating device that converts electrical energy to mechanical energy.

Electric generator: A generator converts mechanical energy into electrical energy.

Alternate Current (A.C.): The current which reverses its direction periodically.

Direct Current (D.C.): The current which flows in one direction only.

Earth Wire: Protects us from electric shock in case of leakage of current especially in metallic body appliances. It provides a low resistance path for current in case of leakage of current.

Short Circuit: When live wire comes in direct with neutral wire accidently.

Overloading: When current drawn is more than current carrying capacity of a conductor, it results in overloading.