Explore CBSE Notes

Exploring Magnets

Chapter 4. Exploring Magnets

Magnets are among the most fascinating discoveries in science. They have the unique ability to attract certain materials without touching them. From simple refrigerator doors to electric motors and magnetic compasses, magnets play an important role in our daily lives. In this chapter, you will learn about magnetic and non-magnetic materials, different types of magnets, magnetic poles, the properties of magnets, the Earth's magnetism, and the various uses and care of magnets.

CBSE Notes - Key Points

This section provides the most important keywords, definitions, scientific terms, facts, and revision points from the chapter. It is useful for quick revision before school examinations and CBSE assessments.

Important Keywords

• Magnet
• Magnetism
• Magnetic Materials
• Non-Magnetic Materials
• Natural Magnet
• Artificial Magnet
• Lodestone
• Bar Magnet
• Horseshoe Magnet
• Ring Magnet
• Disc Magnet
• North Pole
• South Pole
• Magnetic Pole
• Magnetic Compass
• Magnetic Needle
• Magnetic Field
• Earth's Magnetism
• Attraction
• Repulsion
• Matsya Yantra

Important Definitions

Magnet: A magnet is an object that attracts magnetic materials such as iron, nickel, and cobalt.

Magnetism: The property by which a magnet attracts certain materials is called magnetism.

Magnetic Materials: Materials that are attracted by a magnet are called magnetic materials.

Non-Magnetic Materials: Materials that are not attracted by a magnet are called non-magnetic materials.

Natural Magnet: A naturally occurring magnet found in nature is called a natural magnet or lodestone.

Artificial Magnet: A man-made magnet prepared in different shapes for various purposes is called an artificial magnet.

Magnetic Pole: The two ends of a magnet where the magnetic force is strongest are called magnetic poles.

Magnetic Compass: A magnetic compass is an instrument used to find directions with the help of a freely rotating magnetised needle.

Attraction: The force by which unlike poles of magnets pull each other is called attraction.

Repulsion: The force by which like poles of magnets push each other away is called repulsion.

Scientific Terms

English Term	Description
Magnet	An object that attracts magnetic materials.
Magnetism	The property of attracting magnetic materials.
Magnetic Pole	The North and South ends of a magnet.
Magnetic Compass	An instrument used to determine directions.
Magnetic Field	The region around a magnet where magnetic force acts.
Attraction	Pulling force between unlike poles.
Repulsion	Pushing force between like poles.
Lodestone	A naturally occurring magnet.
Earth's Magnetism	The property of the Earth acting like a giant magnet.

Important Facts

• Magnets attract iron, nickel, cobalt, and some of their alloys.
• Wood, plastic, rubber, glass, paper, and cloth are non-magnetic materials.
• Every magnet has two poles—North Pole and South Pole.
• The magnetic force is strongest at the poles of a magnet.
• A single magnetic pole cannot exist independently.
• A freely suspended magnet always comes to rest in the north-south direction.
• The Earth behaves like a giant magnet.
• A magnetic compass works because of the Earth's magnetic field.
• Like poles repel each other, while unlike poles attract each other.
• Repulsion is the surest test to identify a magnet.
• Magnetic force can pass through several non-magnetic materials such as wood, plastic, cardboard, and glass.
• Magnets are used in household appliances, industries, transportation, medicine, and scientific instruments.
• Heating, hammering, or dropping a magnet may reduce its magnetic strength.
• Bar magnets should be stored with soft iron keepers to preserve their magnetism.

Quick Revision

• Magnets attract only magnetic materials.
• Iron, nickel, and cobalt are magnetic materials.
• Every magnet has two poles.
• Magnetic force is maximum at the poles.
• Like poles repel each other.
• Unlike poles attract each other.
• Repulsion is the surest test of a magnet.
• A freely suspended magnet always points in the north-south direction.
• The Earth acts like a giant magnet.
• A magnetic compass is used to find directions.
• Magnetic force can act through some non-magnetic materials.
• Magnets should not be heated, hammered, or dropped.
• Proper storage helps magnets retain their magnetic strength.

Exploring Magnets

Chapter 4. Exploring Magnets

Magnets are special objects that attract certain materials such as iron. They are used in many everyday objects like compasses, refrigerator doors, speakers, and electric motors. This chapter explains the properties, types, and uses of magnets.

Detailed Notes

Magnets

Magnet: A magnet is an object that attracts magnetic materials such as iron, nickel, and cobalt.

Examples of Magnets

(i) Bar Magnet

(ii) Horseshoe Magnet

(iii) Ring Magnet

(iv) Disc Magnet

Characteristics of Magnets

(i) Attract magnetic materials.

(ii) Have two magnetic poles.

(iii) Produce a magnetic field.

(iv) Exert force without touching objects.

Magnetism

Magnetism: The property of a magnet to attract magnetic materials is called magnetism.

Magnetic Materials

(i) Iron

(ii) Nickel

(iii) Cobalt

(iv) Steel

Non-Magnetic Materials

(i) Wood

(ii) Plastic

(iii) Glass

(iv) Rubber

(v) Paper

Natural Magnets

Natural Magnet: A natural magnet is a magnet found in nature.

Example

(i) Lodestone

Characteristics of Natural Magnets

(i) Found naturally.

(ii) Have weak magnetic strength.

(iii) Attract magnetic materials.

Artificial Magnets

Artificial Magnet: An artificial magnet is a magnet made by humans for different purposes.

Common Shapes of Artificial Magnets

(i) Bar Magnet

(ii) Horseshoe Magnet

(iii) Ring Magnet

(iv) Disc Magnet

(v) Cylindrical Magnet

Characteristics of Artificial Magnets

(i) Stronger than natural magnets.

(ii) Available in different shapes.

(iii) Used in many devices and machines.

Magnetic Materials

Magnetic Materials: Materials that are attracted by a magnet are called magnetic materials.

Examples of Magnetic Materials

(i) Iron

(ii) Nickel

(iii) Cobalt

(iv) Steel

Characteristics of Magnetic Materials

(i) Are attracted by magnets.

(ii) Can be magnetised.

(iii) Used to make many tools and machines.

Non-Magnetic Materials

Non-Magnetic Materials: Materials that are not attracted by magnets are called non-magnetic materials.

Examples of Non-Magnetic Materials

(i) Wood

(ii) Plastic

(iii) Glass

(iv) Rubber

(v) Cloth

Characteristics of Non-Magnetic Materials

(i) Are not attracted by magnets.

(ii) Cannot be magnetised.

(iii) Used to make many household objects.

Key Points

(i) Magnets attract only magnetic materials.

(ii) Magnetism is the attractive property of a magnet.

(iii) Magnets are of two types—natural and artificial.

(iv) Lodestone is a natural magnet.

(v) Artificial magnets are stronger and widely used.

Magnetic Poles

Magnetic Poles: The two ends of a magnet where the magnetic force is strongest are called magnetic poles.

Types of Magnetic Poles

(i) North Pole (N)

(ii) South Pole (S)

Characteristics of Magnetic Poles

(i) Every magnet has two poles.

(ii) Magnetic force is strongest at the poles.

(iii) Poles always exist in pairs.

(iv) A single pole cannot exist alone.

Properties of Magnets

Properties of Magnets: Magnets have special characteristics that make them different from ordinary objects.

Main Properties of Magnets

(i) Attract magnetic materials.

(ii) Have two magnetic poles.

(iii) Like poles repel each other.

(iv) Unlike poles attract each other.

(v) A freely suspended magnet points in the north-south direction.

Attraction

Attraction: The force by which unlike poles of two magnets pull each other is called attraction.

Examples of Attraction

(i) North Pole attracts South Pole.

(ii) South Pole attracts North Pole.

Repulsion

Repulsion: The force by which like poles of two magnets push each other away is called repulsion.

Examples of Repulsion

(i) North Pole repels North Pole.

(ii) South Pole repels South Pole.

Important Fact

(i) Repulsion is the surest test of a magnet.

Attraction and Repulsion of Magnetic Poles

Poles	Result
North – North	Repulsion
South – South	Repulsion
North – South	Attraction
South – North	Attraction

Earth as a Giant Magnet

Earth as a Giant Magnet: The Earth behaves like a giant magnet because it has its own magnetic field.

Importance of Earth's Magnetism

(i) Helps in finding directions.

(ii) Makes a compass work.

(iii) Helps travellers and sailors in navigation.

Magnetic Compass

Magnetic Compass: A magnetic compass is an instrument used to find directions.

Parts of a Magnetic Compass

(i) Magnetised needle.

(ii) Pivot.

(iii) Compass box.

Uses of a Magnetic Compass

(i) Finding directions.

(ii) Navigation.

(iii) Surveying.

(iv) Trekking and mountaineering.

Working of a Compass

(i) The needle rotates freely.

(ii) It always points in the north-south direction.

(iii) It works due to the Earth's magnetic field.

Key Points

(i) Every magnet has a North Pole and a South Pole.

(ii) Like poles repel each other.

(iii) Unlike poles attract each other.

(iv) Repulsion is the surest test of a magnet.

(v) A compass helps us find directions.

(vi) The Earth behaves like a giant magnet.

Magnetic Force

Magnetic Force: Magnetic force is the force with which a magnet attracts or repels another magnet or magnetic material.

Characteristics of Magnetic Force

(i) Acts without touching the object.

(ii) Is strongest near the poles.

(iii) Can attract magnetic materials from a distance.

Magnetic Force Through Different Materials

Magnetic Force Through Materials: Magnetic force can pass through some non-magnetic materials.

Materials Through Which Magnetic Force Can Pass

(i) Paper

(ii) Plastic

(iii) Glass

(iv) Cardboard

(v) Thin wood

Important Fact

(i) Magnetic force cannot pass through thick iron objects.

Uses of Magnets

Uses of Magnets: Magnets are used in many devices at home, in schools, industries, and hospitals.

Common Uses of Magnets

(i) Magnetic compass.

(ii) Refrigerator doors.

(iii) Cupboard locks.

(iv) Electric motors.

(v) Electric generators.

(vi) Speakers and microphones.

(vii) Headphones.

(viii) Mobile phones.

(ix) Magnetic cranes.

(x) MRI machines.

Care of Magnets

Care of Magnets: Magnets should be handled carefully to keep their magnetic strength.

Precautions

(i) Do not heat magnets.

(ii) Do not hammer magnets.

(iii) Do not drop magnets.

(iv) Keep magnets away from electronic devices.

(v) Store bar magnets in pairs with unlike poles facing each other.

(vi) Use soft iron keepers while storing magnets.

Loss of Magnetism

Loss of Magnetism: A magnet may lose its magnetic strength if it is heated, hammered, or dropped repeatedly.

Causes of Loss of Magnetism

(i) Heating.

(ii) Hammering.

(iii) Dropping the magnet.

(iv) Improper storage.

Quick Revision

(i) Magnets attract magnetic materials such as iron, nickel, and cobalt.

(ii) Every magnet has two poles—North Pole and South Pole.

(iii) Like poles repel, while unlike poles attract.

(iv) A freely suspended magnet always points in the north-south direction.

(v) The Earth behaves like a giant magnet.

(vi) A magnetic compass is used to find directions.

(vii) Magnetic force can pass through materials like paper and plastic.

(viii) Magnets are used in electric motors, speakers, cranes, and MRI machines.

(ix) Heating, hammering, and dropping can weaken a magnet.

(x) Proper care helps a magnet retain its magnetic strength for a long time.

Exploring Magnets

Chapter 4. Exploring Magnets

In this chapter, you have learnt about magnets, magnetic and non-magnetic materials, magnetic poles, properties of magnets, Earth's magnetism, magnetic compass, attraction and repulsion, and the uses and care of magnets. The following assignment is designed to strengthen your understanding and improve your problem-solving skills according to the latest CBSE pattern.

Assignments - What Have You Learned?

Attempt all the following questions without referring to the textbook. These questions will help you revise the chapter thoroughly and prepare confidently for examinations.

Test Your Learning

Fill in the Blanks

1. A magnet attracts __________ materials.
2. The two ends of a magnet are called __________.
3. A freely suspended magnet always points in the __________ direction.
4. Like poles __________ each other.
5. Unlike poles __________ each other.
6. The Earth behaves like a giant __________.
7. A compass contains a __________ needle.
8. Iron is a __________ material.
9. Wood is a __________ material.
10. The magnetic force is strongest at the __________ of a magnet.

True or False

1. Every magnet has only one pole.
2. Iron is attracted by a magnet.
3. Like poles attract each other.
4. Unlike poles repel each other.
5. A compass is used to find directions.
6. The Earth has its own magnetic field.
7. Plastic is a magnetic material.
8. Repulsion is the surest test of a magnet.
9. Magnets should be heated to increase their strength.
10. Magnetic force can pass through cardboard.

Match the Following

Column A	Column B
Magnet	Attracts iron
Compass	Finds directions
North Pole	One end of a magnet
Lodestone	Natural magnet
Repulsion	Like poles

One Word Answer

1. A naturally occurring magnet.
2. The instrument used to find directions.
3. The property by which magnets attract certain materials.
4. The metal most commonly attracted by magnets.
5. The strongest region of a magnet.
6. The force between unlike poles.
7. The force between like poles.
8. The direction shown by a freely suspended magnet.
9. A material not attracted by magnets.
10. The giant magnet on which we live.

Very Short Answer Questions

1. What is a magnet?
2. Name any two magnetic materials.
3. Name any two non-magnetic materials.
4. How many poles does a magnet have?
5. What is a magnetic compass?
6. Why does a compass needle point north-south?
7. Which poles attract each other?
8. Which poles repel each other?
9. Why is repulsion called the surest test of a magnet?
10. Why should magnets be stored carefully?

Short Answer Questions

1. Differentiate between magnetic and non-magnetic materials with suitable examples.
2. Describe the important properties of magnets.
3. Explain how a magnetic compass works.
4. Why is the Earth called a giant magnet?
5. Explain attraction and repulsion with examples.
6. How can you identify the poles of an unmarked magnet?
7. Describe how a simple magnetic compass can be made.
8. Why is magnetic force strongest at the poles?
9. Write any five uses of magnets.
10. Explain the precautions that should be taken while handling magnets.

Long Answer Questions

1. Explain the different types of magnets and describe their important properties.
2. Describe the construction and working of a magnetic compass with a labelled diagram.
3. Explain the classification of materials into magnetic and non-magnetic materials with examples.
4. Discuss the various applications of magnets in daily life, science, medicine, and industry.
5. Describe the care and storage of magnets and explain why proper handling is important.

Case Study Based Questions

Case Study: Rahul visited a science laboratory where he observed different types of magnets. His teacher suspended a bar magnet freely using a thread. After a few seconds, the magnet came to rest in the north-south direction. The teacher then brought another magnet close to it. Rahul noticed that sometimes the magnets attracted each other, while at other times they repelled each other.

1. Why did the freely suspended magnet come to rest in the north-south direction?
2. What does this activity tell us about the Earth?
3. Under what condition did the magnets repel each other?
4. Which property of magnets is demonstrated in this activity?
5. Why is repulsion considered the surest test of a magnet?

Competency Based Questions

1. Collect five objects from your classroom and classify them as magnetic or non-magnetic with proper reasons.
2. Prepare a simple magnetic compass using household materials and explain how it works.
3. Observe the use of magnets in your home and prepare a list of at least eight applications.
4. Design a simple experiment to show that magnetic force can pass through non-magnetic materials.
5. Prepare a comparison chart showing the differences between natural magnets and artificial magnets.

HOTS Questions (Higher Order Thinking Skills)

1. If magnets had only one pole instead of two, how would their behaviour change? Explain your answer.
2. Why do you think modern electronic devices should be kept away from strong magnets?
3. Imagine the Earth suddenly lost its magnetic field. What difficulties would travellers, birds, and animals face?
4. How would life be different if magnets did not exist? Explain with suitable examples.
5. Suggest five innovative ways in which magnets can be used to solve real-life problems in the future.