Magnets are fascinating objects. A magnet attracts things made of iron, like pins, nails, and paper clips. We see magnets in our daily lives in door catches, fridge magnets, toys, and even in medical devices like MRI machines. But what makes a magnet special? In this chapter, we explore the wonderful world of magnets.
We begin by learning about the discovery of magnets and how to identify them. We study the different shapes of magnets, the poles of a magnet, and the way magnets attract and repel each other. We also learn about magnetic and non-magnetic materials, and how a magnet is used to find directions.
We learn about the Earth as a giant magnet and how a freely suspended bar magnet always points north-south. This is the principle behind the magnetic compass, which sailors and travellers have used for centuries to find directions.
The story of the magnet begins in the ancient region of Magnesia in Greece, where a shepherd named Magnes discovered a natural stone that attracted iron. This stone was named magnetite, and it was the first natural magnet.
Later, people found that when this stone was freely suspended, it always pointed in the north-south direction. This discovery led to the invention of the magnetic compass, which helped sailors navigate the seas.
Over time, humans learned to make magnets from iron and steel. Today, magnets are made in many shapes and sizes, and they are used in many devices. Natural magnets are rare, so most magnets we use today are artificial magnets.
Materials can be classified according to whether they are attracted by a magnet.
Magnetic materials: Materials that are attracted to a magnet are called magnetic materials. Iron, cobalt, nickel, and steel are magnetic materials. Objects made of these materials, like pins, nails, and paper clips, are attracted to a magnet.
Non-magnetic materials: Materials that are not attracted to a magnet are called non-magnetic materials. Wood, plastic, paper, rubber, glass, and aluminium are non-magnetic materials. A magnet cannot attract them.
It is important to note that not all metals are magnetic. For example, aluminium and copper are metals, but they are not attracted to magnets.
Magnets can be classified into two main types:
Natural magnets: Natural magnets are found in nature. Magnetite is a natural magnet found in rocks.
Artificial magnets: Artificial magnets are made by humans from iron and steel in various shapes. Common shapes are: - Bar magnet: A rectangular bar shaped like a rod. - Horseshoe magnet: A magnet shaped like a U or a horseshoe. - Disc magnet: A flat, disc-shaped magnet. - Ring magnet: A ring-shaped magnet. - Cylindrical magnet: A rod-shaped magnet.
Artificial magnets are used in speakers, motors, door catches, toys, and many other devices.
Every magnet has two poles: the North pole and the South pole. - The poles are the ends of the magnet where the attraction is strongest. - If a bar magnet is dipped in iron filings, the maximum filings stick at the two poles, and very few stick in the middle. - The pole that points towards the north when the magnet is freely suspended is the North pole, and the pole that points towards the south is the South pole.
The poles of a magnet cannot be separated. If we break a bar magnet into two pieces, each piece becomes a complete magnet with its own North and South poles. This is true however many times we break the magnet.
The interaction between two magnets follows an important rule: - Like poles repel: North pole repels North pole, and South pole repels South pole. - Unlike poles attract: North pole attracts South pole.
When we bring the North pole of one magnet near the North pole of another magnet, they push each other away (repel). When we bring the North pole of one magnet near the South pole of another, they pull towards each other (attract).
The rule "like poles repel, unlike poles attract" is one of the most important facts about magnets. Repulsion is the sure test of magnetism. If two objects repel each other, both must be magnets.
A freely suspended bar magnet always comes to rest pointing in the north-south direction. This is because the Earth behaves like a giant magnet with a North pole and a South pole.
When a bar magnet is freely suspended, its North pole points towards the Earth's North pole, and its South pole points towards the Earth's South pole. This property of magnets is used in the magnetic compass.
A magnetic compass has a tiny freely suspended magnetic needle. The needle always points north-south. Sailors, explorers, and hikers use the compass to find directions. The compass is one of the oldest and most useful navigational instruments.
We can make a magnet in two simple ways: - Single touch method: A steel bar is rubbed with one pole of a magnet from one end to the other, in a single direction, several times. The steel bar becomes a magnet. - Double touch method: Two magnets are used, and their opposite poles are placed together and rubbed from the centre of the steel bar towards the two ends.
Magnets can also be made by stroking with a strong magnet. The magnetism can be lost by dropping the magnet, heating it, or hammering it. We should take care of magnets to keep their magnetism.
Magnets are delicate and can lose their magnetism if not handled properly. The following precautions should be taken: - Store magnets with their unlike poles together (North to South). - Keep a piece of soft iron across the poles of a bar magnet or horseshoe magnet when not in use. This is called a keeper. - Do not drop magnets, hammer them, or hit them hard. - Do not heat magnets, as high temperature destroys magnetism. - Keep magnets away from CDs, credit cards, mobile phones, and televisions, because magnets can damage these devices.
By taking care of magnets, we can use them for a long time.
Magnets are used in many places: - Door catches use magnets to keep doors closed. - Fridge magnets hold notes and pictures on the refrigerator. - Toys and board games use magnets. - Electric motors, generators, and speakers use magnets. - Magnetic compasses help in navigation. - Magnetic strips on credit cards store information. - Magnets are used in cranes at junkyards to lift heavy iron and steel scrap. - In medicine, MRI machines use large magnets to take pictures of the inside of the body.
Magnets are truly amazing tools that make our lives easier in countless ways.
| Type of Material | Example | Attracted by Magnet |
|---|---|---|
| Magnetic | Iron, cobalt, nickel, steel | Yes |
| Non-magnetic | Wood, plastic, paper, aluminium | No |
| Interaction | Result |
|---|---|
| North - North | Repel |
| South - South | Repel |
| North - South | Attract |
| South - North | Attract |
In this chapter, we had fun learning about magnets. We discovered that natural magnets like magnetite were found in Magnesia, and that today we use artificial magnets in many shapes. We learned that magnetic materials like iron, cobalt, and nickel are attracted to magnets, while non-magnetic materials like wood and plastic are not. Every magnet has a North and a South pole, and like poles repel while unlike poles attract. We saw that a freely suspended magnet points north-south, making the magnetic compass possible. We also learned how to make magnets and how to care for them. Magnets are not just toys; they are powerful tools used everywhere from our homes to hospitals, and their magic lies in the invisible forces of attraction and repulsion.