MAGNETISM Teacher: Lourdes Valencia Bergaz Subject: Science Students: Primary year 6 School: CEIP “Narciso Alonso Cortés” Valladolid
THE EXPERIMENTAL METHOD Previous knowledge: What is a force? What effects do forces produce on objects? What type of forces do you know about? Do you know what a magnet is? Form hypotheses: By making predictions. Design and conduct the EXPERIMENTS Analyze the results of the experiments Draw a conclusion
We are going to study one of the most amazing forces: MAGNETISM A bite of History Once upon a time, there was a shepherd called Magnes who lived in Magnesia, a region in Greece. Pliny The Elder (23-79 AD, Roman) wrote this legend about the beginning of magnetism:
One day, Magnes was herding his sheep and he felt tired. He sat down on a black rock and when he wanted to stand up he almost couldn’t, because the nails of his shoes and the metal tip of his staff had stuck to the rock. Lodestone/Magnetite Source: “Magnetismo en el Aula”
This rock is lodestone or magnetite, the only natural magnet found in nature. And this phenomenon is called magnetism. The children are looking at the pieces of magnetite.
Conclusion: IRON, STEEL AND NICKEL ARE MAGNETIC MATERIALS All the magnetic materials are metals. Only some metals were attracted by magnets. The metals attracted by magnets were iron, steel and nickel. Analyze the results of the experiment
Finding out some facts about magnetism. It sticks to the nail Conclusions: The magnet and the nail together behave as a longer magnet. The nail becomes a temporary magnet. This effect is called induced magnetism. Put one end of the iron nail by the magnet. What happens if we place a paper clip at the other end of the nail? Take the nail away from the magnet. Now, place the paper clip by the nail. Is the paper clip attracted by the nail? Does this mean that the nail is a magnet too?
Is the nail attracted by the magnet only when they are together? How can we check this? We can place different objects between the nail and the magnet. A piece of paper A thick plastic tray A piece of cardboard A piece of cork What objects?
Conclusion: When we place an object between the magnet and the nail, depending on the thickness of the object, the magnet attracts the nail or not. Try with other objects.
Comparing the force of different magnets Make your own magnet: Stroke a steel object with a bar magnet about fifty times. Move the Magnet in one direction only, and raise it at the end of each stroke.
Instructions: - Put a ruler on the table. - Place a pin at zero on the ruler. - Put the magnet at 10 cm. Push the magnet slowly towards the pin. - When the pin jumps to the magnet, look at the number beside the magnet. - Write down the distance in the table below. - Repeat all the steps with your magnet and other magnets. Compare the force of the magnet and the force of your magnet.
Not all the magnets have the same force. There are strong magnets and weak ones. The distance is important. If the pin is far away from the magnet, it is not attracted by the magnet. Conclusion: There is a space where the force of the magnet works. This space is called its magnetic field . Each magnet has a different magnetic field. Magnetic field Analyze the results of the experiment
Conclusion: Magnets have two different ends. They are called poles. North and south pole If we put a magnet next to another one they were attracted. But when we change the end of one of the magnets they were repelled. Try to place two magnets together. Place them in different positions. Analyze the results of the experiment
A bite of History The earliest discovery of the properties of lodestone was by the Chinese. They found out that a lodestone would always point in a north-south direction if it was allowed to rotate freely. The Chinese developed the mariner's compass more than 4000 years ago. The earliest mariner's compass consists of a spoon-shaped magnetite object with a smooth bottom, set on a polished copper surface. When pushed it rotated freely and usually came to rest with the handle pointing South. Source: “Magnetismo en el Aula” At the beginning, chinese people used the spoon compass with a magic purpose. They called it ‘The Magic Spoon’.
The handle of the spoon points to the opposite side. Let the spoon rotate freely and when it stops, observe where the handle of the spoon points. Let’s make a Chinese compass. We will need: a spoon a bar magnet a glass plate Let’s see what happens if we turn the magnet round in the Chinese compass.
A bite of History It’s time to talk about Alexander Neckam . He was an English teacher who was interested in the study of natural history. Alexander Neckam (1157-1217) was born in St Albans, Hertfordshire (England) on 8th September, 1157, on the same night as King Richard I. Neckam's mother nursed the prince with her own son, who thus became Richard's fosterbrother. He went to Paris. In 1180, he became a teacher at the university. I t was probably in Paris that Neckam heard how a ship, along with its other stores, must have a needle placed above a magnet, which would rotate until its point faced North, and guide sailors in bad weather or on starless nights. This device was the first floating compass.
Source: “Magnetismo en el Aula” Design your own compass. Here you have same examples.
The children are designing and making their own compasses
All of them are parallel and pointing to the same direction. The north pole of the magnet in the compasses points to the North; and the south pole of the compasses points to the South. Leave them to rotate freely. What happens when they stop moving? Let’s check the direction by looking at a real compass. What can you see?
Because the Earth is like a very big magnet, and it has its own magnetic field. Act as a compass: look at the compass and face North. Your back points South. Stretch your arms. Your right arm points East and your left arm points West. Now we know where the north pole is in our magnet. Make a red cross on the north pole of your magnet. Why do all the compasses orientate in the same north-south direction?
Let´s work with two magnets again. Which poles attract each other? Which poles repel each other? Analyze the results of the experiment Two magnets with unlike poles facing attract each other. Two magnets with like poles facing repel each other.
Conclusion: The Earth behaves like a gigant magnet. It has a north and south magnetic pole. The north magnetic pole is located in the south geographic pole of the Earth, and the south magnetic pole is located in the north geographic pole of the Earth. The north pole of the compass points to the North Pole of the Earth because it is attracted by the south magnetic pole of the Earth.
A bite of History The first attempt to separate fact from superstition came in 1269 when a French soldier named Peter Peregrinus wrote a letter describing everything that was known, at that time, about magnetite. It is said that he did this while standing guard outside the walls of Lucera which was under siege. While people were starving to death inside the walls, Peter Peregrinus was outside writing one of the first 'scientific' reports and one that was to have a vast impact on the world. He was one of the few medieval scientists to have conducted experimental methods. Source: “Magnetismo en el Aula”
A model of the Earth You will need: a plasticine ball a bar magnet some iron filings The poles of the Earth have a strong force of attraction. Let’s do some of his experiments. What have we checked? Sprinkle some iron filings on your model of the Earth.
Lines of force in a magnetic field a) Put a bar magnet under a sheet of paper. b) Sprinkle some iron filings over the paper. c) Tap the paper gently. The iron filings are attracted to the magnet and form a pattern. This pattern shows what the magnetic fields looks like. Pictures they have drawn of the lines of force. Follow the instructions and do worksheet ‘Fields of force’
a) Place a bar magnet on a sheet of paper and slowly drag the compass around the magnet. b) Draw arrows in the same direction that the compass points to. You can also draw the lines of force by using a compass.
So The Earth behaves as a magnet, we can draw the lines of force in the Earth’s magnetic field as in this picture . Conclusion: The lines of force go away from the north pole of a magnet and towards its south pole. The iron filings draw a pattern of lines. The lines go from one pole to the other From the north pole to the south Analyze the results of the experiment In what direction?
Can we separate the poles of a magnet? Let’s try. Follow these instructions: <ul><li>Unfold a steel paper clip, you will have a piece of </li></ul><ul><li>steel wire. </li></ul><ul><li>Magnetize it. </li></ul><ul><li>Ask your teacher to cut the wire into small pieces with pliers. </li></ul>Place different pieces of wire together. What have you noticed? Each small piece of wire is like a complete magnet. Source: “Magnetismo en el Aula”
It’s imposible to separate the north and the south pole of a magnet All small pieces of wire have a north and a south pole Because a magnet works as if it has little magnets inside it. Analyze the results of the experiment How can you explain this? Conclusion : All magnets have a north and a south pole, because they are made of tiny magnets called magnetic domains with both poles.
Is it posible to change the polarity of a magnet? a) Magnetize a needle. b) Hang the needle from a string and leave it to rotate freely. c) When it stops, check with a compass where the north pole is. d) Put a strong magnet by the needle, and leave it to rotate freely. e) When it stops, check again where the north pole is. Let’s try.
Worksheets they have done: ‘Record experiment worksheet’
Conclusion : Weak magnets can reverse their polarity by the action of a strong magnetic field. At the beginning, the tip of the needle points north But when we put the strong magnet by the needle, the tip points south. The poles of the needle have swaped Analyze the results of the experiment
Facts we have discovered about magnetism: 1.- Magnetism is a force of attraction between magnets and magnetic materials and it works at a distance. 3.- Magnetic materials become a magnet when they are next to it, this effect is called induced magnetism. 2.- Magnets attract only some materials called magnetic ones. 4.- The force of a magnet can pass through thin objects such as paper, cardboard or plastic. 5.- Every magnet has a magnetic field around it. 6.- Every magnet has two poles, a north and south pole.
7.- Unlike poles attract each other and like poles repel each other. 8.- The Earth is a huge magnet. It has two magnetic poles and it is surrounded by a magnetic field. 9.- The Earth’s magnetic field is what causes the needle of a compass to point either north or south. 10.- The magnetic field is made up of lines of force running from the north pole to the south pole of the magnet. 11.- It’s imposible to separate the two poles of a magnet, because magnets are made of very tiny magnets called magnetic domains. 12.- Magnets with a weak force can reverse their polarity thruogh the action of a strong magnetic field.
And next…. ELECTRICITY and the relactionship between ELECTRICITY and MAGNETISM