Presentation on theme: "The English word ‘magnet’ comes from the ‘magnetite’, a naturally ocurring mineral with magnetic properties. Magnets work both under water. Their power."— Presentation transcript:
The English word ‘magnet’ comes from the ‘magnetite’, a naturally ocurring mineral with magnetic properties. Magnets work both under water. Their power of attraction is so intense it can pass through most non magnetic materials. A magnet can be neutralised by using various layers of non magnetic material. Their power of attraction can overcome the power of gravity. Magnetism can be transmitted to other objects. Magnetism Image from: freegraphicdownload.com
The magnetic poles The biggest magnet we know is our planet Earth. The magnetic metals in the centre of the Earth have turned it into a giant magnet. Just like a magnet, the strongest magnetic force is concentrated in the extremes, that is to say, the poles. The magnetic poles don’t coincide with the geographical poles: they are approximately 2,000 km apart. Opposite poles attract; like poles repel. - All magnets move so that one end points north, and the other end points south. This is because of the magnetic force of the Earth. This is what makes a compass works. Can you make a connection between the objects you can see in the photo? Do you know who invented the compass, when & why?
Theme 2: Opposite poles attract, like poles repel - The magnetic car You will need: 2 red & white bar magnets A toy car Preparation: Fix a magnet to the roof of a toy car and bring another magnet close to the one on the car. Predict: what do you think will happen? - Can you push the car? - Can you pull the car? Think: Why does the car move What if... you try to push the car using the side of the magnet instead of the pole? Explanation: - Like poles repel, and will push the car away. - The strongest magnetic force is concentrated in the extremes, so it’s difficult to move the car if you use the sides of the magnets. Practical uses: Trains like the AVE use one magnet on the rails and the opposite pole under the train so the train‘floats’. Since there is no friction, the train can reach a much higher speed.
Experiments with magnets II Magnetic attraction You will need: – a variety of objects, saucepans, coins & rocks. – a magnet. Which objects are magnetic? Which aren’t? Is the magnetic attraction the same in all the objects? WHY do some objects attract and others don’t?
Theme 1: Some materials are magnetic; others attract magnets - You will need: A strong magnet A variety of objects: try to include a rock with iron ore and …... Preparation: Make a chart with the name of the object and three columns: strong, weak and inexistant attraction. Predict: What attraction will each object have? Think: Did you predict correctly? Analyse your mistakes and try to explain them. What if... Explanation: -. Practical uses: Induction cookers only work with…...
Experiments with magnets III A DIY compass You will need: - A needle - A magnet - A small circle (3cm) of wax-paper (or similar) - A bowl of water Magnetize the needle by rubbing one end with the north tip and the bottom end with the south tip about 40 times. (Rub from the centre to the end and lift the magnet away as you go to repeat the stroke) Stick the needle into paper as if you were sewing. Float the paper with the needle in the middle of the bowl of water. Watch what happens. Move the paper around and watch again Can you explain what is happening? Can you expain why? Can you prove that this is because the needle is magnetized?
Experiments with magnets IV Magnetic force You will need: - Either a steel wool pad cut into small pieces, or iron shavings - A piece of card - A rectangular or a horseshoe magnet (or both!) Put the card on top of the magnet. Sprinkle the iron shavings over the card. Gently tap the card. What happens? Are the shavings attracted equally or irregularly? Why? What have you proved? Can you now explain why a compass works?
Experiments with magnets V Magnetism can be transmitted You will need: A magnet A few paper clips or nails Attract a clip to the magnet. Put the clip next to a another one – what happens? Separate the first clip from the magnet just a little bit – does the bottom clip remain attatched or fall off? Move the magnet further away – now what happens?
Experiments with magnets VI Underwater magnetism You will need: - a magnet - a jar of water - a paperclip Drop the clip into the water. Can you get it out without getting your fingers wet?! What have you just demonstrated? Can you think of any situation where this could be useful? What if… you used a metal jar instead of a glass one?
Experiments with magnets VII Magnetism works through materials You will need - a big sheet of card, paper and paints - 2 metal washers - 2 magnets on a long stick If magnetism works through materials…can you invent a game based on magnetism?