magnet

Who discovered the magnet?

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Who discovered the magnet?

According to a legend, the first magnet was discovered by a Greek shepherd named Magnes. It is said that the nails in his shoes and the iron tip of his staff got stuck to a large black rock on which he was standing. Greeks named this strange type of rock ‘magnetite’. The Chinese also knew about magnets. Ancient Chinese sailors used magnets for navigation.

How do they make a magnet?

Magnets are made of materials that attract objects made of certain substances like iron, cobalt, and nickel. Magnets come in various shapes and sizes. They can be found as horseshoe, ring, cylindrical, or bar shape.

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Shapes of magnet

Not all objects are attracted to magnets. Objects that are attracted by a magnet are said to be magnetic, e.g., iron and nickel. Objects that are not attracted by a magnet, are said to be non-magnetic, e.g., wood and plastic.

POLES OF A MAGNET
When magnetic materials (like iron filings) are brought close to a magnet, they do not stick evenly to all parts of the magnet. They stick more on certain parts of the magnet. These are called the poles of the magnet. Magnetic forces are the strongest at the poles. For example, the two ends of a bar magnet are its poles.
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). The two poles cannot exist independently. That is, they always come in pairs.

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Poles of bar magnet

If we break a bar magnet in the middle, we would get two pieces, each having a North Pole and a South Pole. We could go on breaking the magnet into smaller pieces, and everytime we would get both the poles in each piece.

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Activity

Aim: To find the poles of a magnet.
Materials needed: Iron filings (powdered iron), a magnet, a small sheet of transparent polythene, and a sheet of white paper.
Method:
1. Spread the iron filings on a sheet of white paper.
2. Wrap the magnet in the polythene sheet and run it through the iron filings.
Who discovered the magnet 3Observation: Most of the iron filings will stick to two portions of the magnet.
Conclusion: The two portions of the magnet where most of the iron filings stick are the poles of the magnet.

How can we Separate a Mixture of Two Solids

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How can we Separate a Mixture of Two Solids

Many of the materials around us are mixtures. These mixtures have two or more than two substances mixed in them. It may not be possible to use a mixture as such in homes and in industries. We may require only one (or two) separate constituents of a mixture for our use. So, we have to separate the various mixtures into their individual constituents to make them useful in our daily life.

Separation of mixture of two solids
All the mixtures containing two solid substance can be separated by one of the following methods:

1. Separation by a suitable solvent : In some cases, one constituent of a mixture is soluble in a particular liquid solvent whereas the other constituent is insoluble in it. This difference in the solubilities of the constituents of a mixture can be used to separate them.
Ex.       Sugar is soluble in water whereas sand is insoluble in it, so a mixture of sugar and sand can be separated by using water as solvent.

2. Separation by sublimation : The changing of a solid directly into vapours on heating, and of vapours into solid on cooling is called sublimation. The solid substance which undergoes sublimation is said to ‘sublime’. The process of sublimation is used to separated those substances from a mixture which sublime on heating. The solid substance obtained by cooling the vapour is known as sublimate.
Ex.       Ammonium chloride, Iodine, Camphor,. can be separated from a mixture by sublimation.
How can we Separate a Mixture of Two Solids 1

3. Separation by a magnet : Iron is attracted by a magnet. This property of iron is used to separate it from a mixture. So, if a mixture contains iron as one of the constituents, it can be separated by using a magnet.
Ex.       A mixture of iron filings and sulphur power can be separated by using a magnet. This is because iron filings are attracted by a magnet but sulphur is not attracted by a magnet.
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