In this blog, we will have fun with magnets! We will learn about the discovery of magnets, magnetic and non magneti materials, poles of magnet, finding directions using magnets and get to know about how to make magnetic compass!

 

How magnets were discovered?

 

The most popular legend accounting for the discovery of magnets is that of a shepherd named Magnes. One day he was herding his sheep in an area of Northern Greece called Magnesia, about 4000 years ago. He was surprised to find that the metal tip of his staff became firmly stuck to the large black rock on the mountainside on which he was standing. He had to pull hard to free his stick from the rock. He found his stick was being attracted by the rock. To find the source of attraction he dug up the earth to find a lodestone.

 

This is how magnets were discovered. Such rock was given the name magnetite. William Gilbert, an English physician first proposed in 1600 AD that the earth itself is a magnet. Substances that attract iron are known as magnets. Later on, the process to convert any piece of iron into a magnet was discovered. Magnets thus formed are called artificial magnets.

 

Artificial or man-made magnets come in various shapes and sizes such as bar magnet, disc magnet, ring magnet, horseshoe magnet, cylindrical magnet, the ball-ended magnet. Isn't it fun with magnets? Let's learn more.

 

Magnetic Compass

 

In chapter fun with magnets, we have learnt that a freely suspended bar magnet always comes to rest in the north � south direction. This property of the magnet is used to find directions. In olden days travelers used to find directions by suspending natural magnet with a thread. Later on a device called compass was developed for finding directions. It is the oldest instrument used for navigation and has been an important tool for navigation at sea for centuries.

 

The early compass consisted of a magnetized iron needle attached to a piece of wood or cork that floated in a bowl of water. The present-day compass consists of a small cylindrical box of aluminum or brass with a glass cover on it. A small lightweight magnetized needle is mounted on a pivot at the center of the box. The North end of the needle is generally painted red. The needle is free to rotate in the horizontal plane.

 

The compass also has a dial with directions marked on it. Setting compass to find directions. The needle of the compass indicates the north-south direction when it is at rest. The compass is rotated until the north marked on the dial is exactly below the north end of the needle. In this position, the dial correctly shows east, west, north, south, and other directions. Make sure that when you are using the compass, no magnet or magnetic material is near it.

 

Magnetic and Non magnetic materials

 

In this chapter of fun with magnets, we will also be learning about magnetic and non magnetic materials.

 

The magnet attracts certain materials and some don�t get attracted towards the magnet. Materials, which get attracted towards a magnet are called magnetic materials such as iron, cobalt, nickel.

 

Materials that are not attracted by a magnet are called non-magnetic materials such as plastic, leather, aluminum, wood, glass, copper.

 

Make your own magnet!

 

A magnetic object can be made into a magnet by the stroking method:

 

1. Take a rectangular piece of iron. Try picking iron fillings with this piece of iron. What do you observe? You will observe that the Iron fillings do not cling to the iron bar.
2. Place the iron bar on the table. Now take a bar magnet and stroke the iron bar down the length 20-30 times with anyone pole of a magnet.
3. Stroke with the same pole and always in the same direction.
4. Bring some iron fillings near the end of the iron bar to check whether it has become a magnet or not. If not, continue stroking some more times.

 

Make your own compass

 

1. Magnetize an iron needle using a bar magnet by the stroking method.
2. Stick the needle through a small piece of cork and place the cork in the center of a bowl of water. Make sure that the needle does not touch the water.
3. Now you have a very simple compass.
4. Keep the water as still as possible.
5. You will find that your compass needle stays in the north-south direction.

 

Poles of Magnet

 

We have learned that magnets attract materials such as iron, cobalt, nickel. Artificial magnets are available in different shapes. Most commonly used magnets are made of ceramic or ferrite. Let us find out more about a magnet.

 

Activity:-

 

1. Spread some iron powder or iron filings on a white cardboard sheet. Now place a bar magnet at the center of the sheet. Sprinkle some more iron filings on and around the magnet. Tap the board 2-3 times. What do you observe?
2. We observe that iron filings are attracted towards the magnet. Iron filings sticking to the regions close to the ends of the bar magnet are more than the iron filings at the other parts of the magnet. This shows that the power of attraction of the bar magnet is not the same at all its parts.
3. The magnetic strength of a bar magnet is maximum at its ends and minimum at its middle part.
4. Now repeat this activity using pins or small size nails in place of iron filings. What do you observe?
5. The result is almost the same.
6. The ends of the bar magnet collect more pins than any other part of the magnet.
7. The two ends, which are the regions of strong magnetic power, are called the poles of the magnet. We can do this activity using magnets of different shapes.

 

Finding Direction Using Magnet

 

Ancient people found that if a lodestone was suspended so that it could rotate freely. It would always point in the same direction. People of the state Zheng always knew their position by means of a south pointer. The south-pointing chariot was an ancient Chinese two-wheeled vehicle that carried a movable statue of a lady with an outstretched arm to indicate the south, no matter how the chariot turned.

 

An emperor in china used such a chariot to locate directions whenever he went to new places.
In a song dynasty book dated to1040-44 there is a description of a south-pointing fish floating in a bowl of water aligning itself to the south.

 

Let us make a direction finder for ourself

 

1. Take a bar magnet. Put a mark on one of its ends. Tie a waxed thread exactly at the middle of the magnet and suspend it from a wooden stand. Adjust the height of the magnet so that it is a little above the ground.
2. Mark the position of the ends of the magnet on the ground when it comes to rest. Draw a line, joining these points.
3. Now push gently any one end of the magnet to its left or right by a small amount what do you observe? The magnet is set into rotation.
4. The magnet comes to rest after making to and fro motion for some time.
5. Again mark the position of its ends on the ground.
6. What do you find? Rotate the magnet once again and note the final direction in which it comes to rest. We find that the magnet always comes to rest in the same direction.
7. Now you understand the mystery behind the statue in the emperor�s chariot and floating south-pointing fish. We find that a freely suspended bar magnet always comes to rest in a particular direction, which is the North-South direction.
8. The end of the magnet that points towards the North is called the North seeking pole or north pole of the magnet. The other end that points towards the south are called the south pole of the magnet or the south seeking pole.
9. The magnetic poles are marked with �S� for the south pole and �N� for the north pole. In addition, the red color for the north pole and the blue color for the south pole are used for pole identification.

 

Some magnets have only the north half of the magnet painted red and the other half unpainted. You will also find some bar magnets completely painted red. A dot mark of the white color is put on the north pole. Magnetic poles always exist in pairs. If a bar magnet is cut into two, each piece will have a north pole and south pole.

 

Magnets Precaution

 

While we end our fun with magnets, let us learn about some magnet safety. Magnets can lose their properties due to various reasons.

 

1. Prolong exposure to heat: A magnet will lose its magnetism if heated for long time.

 

2. Repetitive shock: Magnets can lose their properties if hammered or dropped from some height.

 

3. Poor storage: Two magnets if placed side by side with their like poles on the same side, weaken the magnetic strength of each other.

 

To avoid such situations bar magnets should be kept in pairs with their unlike poles on the same side. They must be separated by a piece of wood or plastic. Two pieces of soft iron should be placed across their ends. A horseshoe magnet requires only one piece of soft iron to join its poles. We hope you had Fun with Magnets and loved to learn about them!

 

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