A magnet produces a type of force that attracts other objects, which are made of iron and nickel. This attractive force is called Magnetism.
The Discovery of Magnets
Around 4000 years ago, while herding his sheep, Magnes' sandals and stick got stuck to large, black rock. It was made of a mineral that had ability to attract objects made of iron. This rock mineral was named Magnes Lithos or LodeStone or Magnetite. The Chinese ships used magnetic spoons on bronze plates with directional bearings, to navigate across seas. In 17th century, the English physician and scientist William Gilbert published On Magnets, and proposed that Earth is a giant magnet. In 19th century, James Clerk Maxwell published a relatively complete explanation of electricity and magnetism. In 20th century, the French physicist Pierre Weiss proposed that there are particles called Magnetrons, equivalent to electrons, that caused the magnetic properties of materials. Humans have found rocks that have the property of attracting objects made of iron and these rocks are called natural magnets. These natural magnets are made up of the mineral magnetite, also called loadstone. Humans also discovered how to create artificial magnets from pieces of iron in various shapes - Bar, horse-shoe or circular magnets.
Magnetic and Non-Magnetic materials
The materials that are attracted by a magnet are called magnetic materials. These are usually made of iron, nickel or cobalt. The materials that are not attracted by a magnet are called non-magnetic materials. For example, wood, ceramic, plastic, glass.
Experiment: When the magnet is brought closer to the iron, nickel or cobalt, then these objects are attracted to the magnet. They jump up and stick to the magnet. The other objects are made of non magnetic materials and have no effect when magnet comes near them.
Properties of a bar magnet
There are 4 basic properties of a bar magnet:
1. Directional Property: A freely suspended magnet always aligns itself in the Earth's North-South direction.
2. Attractive Property: A magnet attracts magnetic materials like iron, iron filings, cobalt and nickel.
3. Attraction and repulsion between magnets: Poles repel and unlike poles attract each other.
4. Paired poles: Poles always exist in pairs.
Steps for making an indoor magnet
Making a magnet using another magnet:
1. Get a needle made of iron.
2. Find a strong, big magnet.
3. Repeatedly run the magnet across the needle in the same direction as shown in the above picture, 75-100 times.
4. Then try picking up small iron filings with the needle. It will be able to pick some of them up.
5. This magnet you made will not last long or be very strong. In the later lessons you will learn how stronger electro-magnets are made.
Different types of magnets and their Uses
Permanent magnets: These magnets are permanent in the sense that once they have been magnetized, they always retain a certain degree of magnetism.
Examples of permanent magnets are commonly used in our daily lives. Magnets along the edge a refrigerator door and in audio speakers are all permanent magnets.
Magnetic materials from which permanent magnets are made are called hard magnetic materials. A lodestone is a naturally occurring permanent magnet composed of magnetite.
Temporary Magnets: A temporary magnet acts as a magnet only as long as it is in the magnetic field produced by a permanent magnet or in the magnetic field induced by an electric current.
Temporary magnets are used in telephones and electric motors amongst other things. Magnetic materials from which temporary magnets are made are called soft magnetic materials.
Every object that is lifted or moved by a magnet acts as a temporary magnet. Such an object ordinarily loses its magnetism when the magnetic field is removed, although in certain cases it will retain weak magnetic properties.
An electromagnet is a temporary magnet that is magnetized by the magnetic field produced by an electric current in a wire.
Poles of a magnet, attractions and repulsion of magnets
When iron filings are brought close to a magnet, they stick more to two parts of a magnet. These two parts are called the Poles of a magnet. In this example of a bar magnet, the two ends are the poles of the magnet. There are two types of poles in every magnet irrespective of its shape. These are, by convention, called the North pole (N) and the South pole (S). They will always exist as a pair on any magnet.
When a magnet is sub-divided into 2 smaller pieces, then each broken piece will still act as a small magnet with its own North and South pole. This is because the smallest particles of a magnet possess the magnetic property, and even when the magnet is broken, the particles in the 2 broken pieces continue to possess the magnetic property.
Directional property - You will find that a freely suspended bar magnet always comes to rest in the North-South direction of the earth. The end of the magnet that points towards North is called its North seeking end or the North pole. The other end that points towards the South is called South seeking end or the South pole of the magnet. A magnet's directional property is used in a mariner's compass.
How magnets lose their magnetic power
A magnet can lose its property due to following reasons:
1) By rough handling
2) By heating it to very high temperature
3) By hammering it violently several times
4) By dropping it on the floor many times from a great height.
The Discovery of Magnets
Around 4000 years ago, while herding his sheep, Magnes' sandals and stick got stuck to large, black rock. It was made of a mineral that had ability to attract objects made of iron. This rock mineral was named Magnes Lithos or LodeStone or Magnetite. The Chinese ships used magnetic spoons on bronze plates with directional bearings, to navigate across seas. In 17th century, the English physician and scientist William Gilbert published On Magnets, and proposed that Earth is a giant magnet. In 19th century, James Clerk Maxwell published a relatively complete explanation of electricity and magnetism. In 20th century, the French physicist Pierre Weiss proposed that there are particles called Magnetrons, equivalent to electrons, that caused the magnetic properties of materials. Humans have found rocks that have the property of attracting objects made of iron and these rocks are called natural magnets. These natural magnets are made up of the mineral magnetite, also called loadstone. Humans also discovered how to create artificial magnets from pieces of iron in various shapes - Bar, horse-shoe or circular magnets.
Magnetic and Non-Magnetic materials
The materials that are attracted by a magnet are called magnetic materials. These are usually made of iron, nickel or cobalt. The materials that are not attracted by a magnet are called non-magnetic materials. For example, wood, ceramic, plastic, glass.
Experiment: When the magnet is brought closer to the iron, nickel or cobalt, then these objects are attracted to the magnet. They jump up and stick to the magnet. The other objects are made of non magnetic materials and have no effect when magnet comes near them.
Properties of a bar magnet
There are 4 basic properties of a bar magnet:
1. Directional Property: A freely suspended magnet always aligns itself in the Earth's North-South direction.
2. Attractive Property: A magnet attracts magnetic materials like iron, iron filings, cobalt and nickel.
3. Attraction and repulsion between magnets: Poles repel and unlike poles attract each other.
4. Paired poles: Poles always exist in pairs.
Steps for making an indoor magnet
Making a magnet using another magnet:
1. Get a needle made of iron.
2. Find a strong, big magnet.
3. Repeatedly run the magnet across the needle in the same direction as shown in the above picture, 75-100 times.
4. Then try picking up small iron filings with the needle. It will be able to pick some of them up.
5. This magnet you made will not last long or be very strong. In the later lessons you will learn how stronger electro-magnets are made.
Different types of magnets and their Uses
Permanent magnets: These magnets are permanent in the sense that once they have been magnetized, they always retain a certain degree of magnetism.
Examples of permanent magnets are commonly used in our daily lives. Magnets along the edge a refrigerator door and in audio speakers are all permanent magnets.
Magnetic materials from which permanent magnets are made are called hard magnetic materials. A lodestone is a naturally occurring permanent magnet composed of magnetite.
Temporary Magnets: A temporary magnet acts as a magnet only as long as it is in the magnetic field produced by a permanent magnet or in the magnetic field induced by an electric current.
Temporary magnets are used in telephones and electric motors amongst other things. Magnetic materials from which temporary magnets are made are called soft magnetic materials.
Every object that is lifted or moved by a magnet acts as a temporary magnet. Such an object ordinarily loses its magnetism when the magnetic field is removed, although in certain cases it will retain weak magnetic properties.
An electromagnet is a temporary magnet that is magnetized by the magnetic field produced by an electric current in a wire.
Poles of a magnet, attractions and repulsion of magnets
When iron filings are brought close to a magnet, they stick more to two parts of a magnet. These two parts are called the Poles of a magnet. In this example of a bar magnet, the two ends are the poles of the magnet. There are two types of poles in every magnet irrespective of its shape. These are, by convention, called the North pole (N) and the South pole (S). They will always exist as a pair on any magnet.
When a magnet is sub-divided into 2 smaller pieces, then each broken piece will still act as a small magnet with its own North and South pole. This is because the smallest particles of a magnet possess the magnetic property, and even when the magnet is broken, the particles in the 2 broken pieces continue to possess the magnetic property.
Directional property - You will find that a freely suspended bar magnet always comes to rest in the North-South direction of the earth. The end of the magnet that points towards North is called its North seeking end or the North pole. The other end that points towards the South is called South seeking end or the South pole of the magnet. A magnet's directional property is used in a mariner's compass.
How magnets lose their magnetic power
A magnet can lose its property due to following reasons:
1) By rough handling
2) By heating it to very high temperature
3) By hammering it violently several times
4) By dropping it on the floor many times from a great height.