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The first magnet was found from the naturally occurring mineral called magnetite. The ancient Greeks were the discoverers of magnetite. There is a story about a shepherd named Magners whose shoe nails stuck to a rock containing magnetite while roaming on Mt. Ida. Later, it was found that the mountain was made of black stone with iron that had a special property to attract iron. It was an ore of iron called magnetite. Magnetite occurs all over the world, but there are especially large deposits in Scandinavia. The magnet was first used as a practical magnetic compass by the Vikings in their travels to colonise or in war. A magnet is a substance made of a certain material that has the capacity to attract magnetic substances like iron, nickel, cobalt, etc. The energy possessed by a magnet is called magnetic energy. We use the magnet in our daily life activities. It is used in loudspeaker, telephone, radio, telegraph, dynamos, toys, electric motors, etc. Magnet has always two poles, south pole, and the north pole. Like pole repels and unlike poles attract. The most powerful magnet in the universe is actually a star called a magnetar. Earth itself is like a one big bar magnet. Some animals are affected by magnets.
There are two types of magnets which are given below,
Bring some pieces of iron and a bar magnet. Then keep the pieces of iron near the bar magnet. What do you observe? What do you conclude from this activity?
Bring a bar magnet and suspend it freely with the help of nylon thread and stand. Then, rotate the magnet and observe the direction of the bar magnet after it comes at rest. Does the magnet show north- south direction after coming at rest? What do you conclude from this experiment?
There are various methods of making magnets. Magnets of desired shapes and sizes can be made artificially by using magnetic substances. Some common methods of making magnets are as follows,
The artificial magnet can be prepared by rubbing strong bar magnet over the surface of magnetic substances for several times. It can be done by two methods,
Electrical method is used for making temporary magnets like an electromagnet. Here, the magnetic substances are magnetised by passing electricity. It consists of a coil made of insulated copper wire that is wound around the magnetic substance. The two ends of the wire are connected with the battery having a switch. When the switch is made on, the current flows through the coil and the magnetic substance becomes a magnet. When the switch is made off, the magnetic substance loses the magnetic properties. The magnets which are made by passing electricity are called electromagnet.
Precaution while making electromagnet
Bring a bar magnet, pieces of iron and a steel bar. Then rub the surface of the steel bar by using the same pole of the bar magnet. Repeat this action for several times for more than half an hour. Then keep the pieces of iron near the steel bar. What do you observe? What do you conclude from this activity?
Bring a long insulated wire, pieces of irons, soft magnetic substance (bar), battery and a switch. Then wind the wire over the bar for several times, join both ends of the wire with the battery and switch. Now keep some pieces of iron near the nails and turn the switch on. What happens to the pieces of iron when you turn switch on and off ? What do you conclude from this experiment?
A magnet is a substance which has the property of attracting iron, cobalt, etc. There are two types of magnet which are as follows;
There are two types of magnet which are as follows:
Any two uses of magnets are as follows,
Any two precautions while making electromagnet are as follows,
Permanent magnets are those magnets which can retain their magnetic properties for a long period of time. Any three devices where permanent magnet is used are as follows;
An electrical method is used for making temporary magnets like an electromagnet. Here, the magnetic substances are magnetised by passing electricity. It consists of a coil made of insulated copper wire that is wound around the magnetic substance. The two ends of the wire are connected with the battery having a switch. When the switch is made on, the current flows through the coil and the magnetic substance becomes a magnet. When the switch is made off, the magnetic substance loses the magnetic properties. The magnets which are made by passing electricity are called electromagnet.
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Any three devices in which electromagnet is used are as follow,
The differences between natural magnet and artificial magnet are as follows,
|Natural magnet||Artificial magnet|
|These are the magnets found naturally on earth.||These magnets are made by humans by using various artificial methods.|
|These magnets has weak force of attraction.||These magnets has strong force of attraction|
|Example; lodestone and magnetite||Example; bar- magnet and magnetic compass|
The differences between permanent magnet and temporary magnet are given below,
|Permanent magnet||Temporary magnet|
|They retain magnetic properties for the long period of time.||They retain magnetic properties for the short period of time.|
|Permanent magnets have the magnetic properties even if the external field is zero.||Temporary magnets have magnetic properties only in the presence of an external magnetic field|
|They are used in electric motor and electric fan.||They are used in radio and tape recorder.|
The differences between bar magnet and electromagnet are given below,
|A bar magnet is a permanent magnet.||The electromagnet is a temporary magnet.|
|There is no need of electricity to retain the magnetic properties.||Electricity is necessary to retain the magnetic properties.|
A freely suspended bar magnet always rests in ___________ direction.
Which one of the following is not the method of making magnet?