Magnets push and pull
Are there some magnets on your fridge door? If there are, take them off and have a look at them. The chances are that they are round magnets like buttons. When you bring a magnet close to the fridge door, you can feel a strong pull. If you bring the magnet closer and let go, the magnet will leap onto the door with a snap. You may think that when you bring two magnets together they will snap even harder together but you would be surprised.

If you place one magnet on a tabletop then bring the other close, you may not see them rush to each other. You will most probably feel a pushing force. You may also see the other magnet start to move about the tabletop as if it was trying to avoid the magnet that you are holding. This pushing and moving may go on for a few moments then, once the magnet on the table has turned a certain way, the two magnets suddenly snap together. Why have the magnets behaved like this?

It is best to think about how the magnets behaved by thinking about bar magnets. These are thick strips of metal a few centimetres long. The magnetic power does not go all along the length of the magnet. If you put a bar magnet in a tray of steel paperclips, the paper clips cluster around the ends. None of them grips the middle of the magnet. This means that the greatest power of the magnet is found around its ends. If a bar magnet is hung horizontally from a thread, another discovery is soon made. One end of the bar points to the north and the other end points to the south.

We can now bring these two pieces of information together. The places where the greatest magnetic power is found are called the poles. They are at the ends of the magnet. The pole in the end of the magnet which points north is called the north-seeking pole or more simply just the north pole. The pole in the end of the magnet which points south is called the south-seeking pole or more simply just the south pole.

If we bring one bar magnet towards another bar magnet, we may feel a push just as you did when you first brought the fridge magnets together. If the second bar magnet is free to move we may see its end swing away from the magnet we are holding. The other end of the magnet may swing round too and snap onto the end of our magnet. This odd behaviour is due to the poles of the magnets. When the magnets push each other away, it is because they both have the same kind of pole in their ends. If two north poles or two south poles are brought together, the pushing force is felt as the two ends repel each other. When the magnets pull each other together they have different poles in their ends. This means that one pole is a north pole and the other is a south pole and the two opposite poles attract each other.

You may notice that the magnets do not have to touch each other before their attraction or repulsion begins. When you hold the magnets far apart, you feel no pushing or pulling forces. However, when you hold the magnets quite close the forces can be felt. This means the magnetic forces act in the air around them. You may wonder if they act through other materials.

It is easy to check if magnetic forces act through other materials like cardboard or plastic. Just put one magnet on one side of the material and the other magnet on the other side. If the north pole of one magnet points into the material on one side and the south pole of another magnet points into the material on the other side, the two magnets are attracted and will hold themselves together, even though the material is in the way. If the north pole of one magnet points into the material on one side and a north pole of another magnet points into the material on the other side, the two magnets repel each other.
If you have some magnets on your fridge, go and investigate them. Find out how they attract and repel each other and how their power can work through other materials.

What would happen if the south pole of one magnet points into the material on one side and a south pole of another magnet points into the material on the other side?
They would repel each other. It is important to remember that
1. Similar poles, such as north and north, or south and south, repel each other.
2. Different or opposite poles, such as north and south, or south and north, attract each other.

If you hang a bar magnet from a thread and let it point north and south, what happens if you bring another magnet near it?
If you bring the north pole of a magnet close to the north pole of the hanging magnet, the hanging magnet will turn away from pointing north. This happens because the two poles are similar and repel each other. If you bring the south pole of a magnet close to the north pole of a hanging magnet, the hanging magnet will turn towards the south pole. This happens because the two poles are different or opposite and they attract each other. In a similar way the south pole of a hanging magnet is turned from a south pole of another magnet but turned towards the magnet when its north pole is brought near.

Why does the hanging bar magnet always point in the same direction?
Because the inside of the Earth behaves as if it has a huge bar magnet inside it. This makes any magnet hanging on a thread line up in the way it does. The magnetic force is so powerful that it can act through the surface of the Earth and in the air around it. In fact the Earth's magnetic power reaches out 60,000 kilometres into space.

Why does a hanging magnet move when another magnet is brought close?
The pulling and pushing power of the magnet in the Earth is not strong. The pulling and pushing power of many other magnets is stronger. When a magnet with a stronger pulling or pushing power than the Earth's magnet is brought to a pole of a hanging magnet, the pole is either attracted or repelled.

Does the power of a magnet work through all materials?
It works through many materials such as wood, plastic, paper, glass and even water.
It does not act through iron and steel.

Can a magnet attract a magnetic material through cardboard?
Yes, it can. A magnet not only attracts or repels another magnet through cardboard: it also attracts magnetic objects such as steel paper clips. In fact the magnet on your fridge door attracts the steel in the fridge door through a postcard or notepaper.

Does the power of a magnet work through any thickness of material?
No. If you put one sheet of card between a magnet and a paper clip, you will find that the paperclip hangs onto the card strongly. If you add a few sheets of card, the paperclip only hangs on weakly and eventually, if you add enough sheets of card, the paperclip will not stick to the cards at all.

Why does the thickness of the card affect the way a magnet can hold onto a paper clip?
The strength of the magnetic force is greatest near the magnet. As you move away from the magnet its power becomes weaker. There is a place at a certain distance from the magnet where the power is too weak to attract a paper clip. When you use cards to test a magnet's power you are finding the distance at which the power is too weak to attract a magnetic material. You could find this distance without using cards. Just bring a paperclip close to a magnet and see where the paper clip suddenly jumps to the end of the magnet. Now repeat the test, but this time measure the distance from where the paperclip jumped and the end of the magnet.