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Download A Magnet is an object with a magnetic force or field that attracts or
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A Magnet is an object with a magnetic force or field that attracts or repels objects. A magnet’s property of attracting material is called magnetism. Magnetism is a force that acts on moving electric charges and magnetic material. Iron and steel are attracted to a magnet. Not all metals are attracted to a magnet. Copper, aluminum, and gold are examples of metals that are NOT attracted to a magnet. There are different kinds of magnets. Ex. bar magnets, horseshoe magnets, circle magnets, and donut magnets (circle with a hole), wand magnet People have many uses for magnets in their everyday lives. They are used to hold things on refrigerators, to close cabinet doors, in a compass, in toys, and to pick up pins or thumbtacks to avoid being stuck. A magnetic screwdriver makes it easier to hold screws in place. MRI’s use magnets to produce pictures of the inside of the body which help doctors identify injuries to muscles and tissues. A Maglev (Magnetic Levitation) train runs on electricity and uses magnetic force to float slightly above the rails or tracks because the magnets are repelling each other. These quiet trains are not slowed down by friction and travel superfast (up to 300 miles per hour). There are two kinds of magnets: 1. A permanent magnet is made in a factory and keeps its magnetism for a very long time. 2. A temporary magnet does NOT keep its magnetism for a very long time. A temporary magnet can be made by stroking a nail many times, very quickly with a permanent magnet. It will then remain magnetic for a very short time. Magnets have a North and South Pole. Like poles (N-N, S-S) of magnets will repel or push away from each other. Unlike poles (N-S, S-N) will attract or pull toward each other. (Opposites attract) A magnet has a force field that you can’t see. The space in which the force of a magnet can act is called its magnetic field. A magnet’s magnetic field spreads out in all directions throughout the space around the magnet. A magnet’s magnetic force is strongest at its poles and gets weaker away from its poles. Scientists have learned the Earth is a giant magnet. Earth’s center is made of mostly iron and the spinning of the Earth on it axis has turned Earth into a giant magnet. The spinning has magnetized the iron at its center Lodestone is a naturally magnetic rock found at or near Earth’s surface. Thousands of years ago, people discovered that when lodestone was hung by a string, one end always pointed north. This was used by Chinese sailors to tell what direction they were sailing. Today a compass is based on the same idea. A compass uses a magnetized needle which is allowed to swing freely. The compass needle points to the Earth’s magnetic north pole. Earth has two sets of poles: 1. Geographic 2. Magnetic They are NOT the same. The Earth’s magnetic north pole can be 500-1200 miles away from its geographic north pole. Ordinary magnets work without an electric current. Electric circuits work without magnets. Hans Christian Oersted discovered there was a relationship between electricity and magnetism which led to the invention of the electromagnet. An electromagnet is a magnet that only works when electricity is provided. To make an electromagnet, you pass an electric current through a coiled wire. The moving electric current creates a magnetic field. The wire loses its magnetism when the current is stopped. Ways to make an electromagnetic stronger: 1. Coil the wire around an iron core Ex.an iron nail 2. Add more coils or wire (the more coils, the stronger, the magnetic field) 3. Increase the amount of electric current running through the wire Electromagnets are useful because you can turn them off when you do not want them to attract objects. There are electromagnets in doorbells, computers, and DVD players and motors in fans and blenders. Moving a magnet within coiled wires produces electricity. A generator is a machine that produces electric energy by turning coils of wire around powerful magnets. A generator turns the energy of motion into electrical energy. Wind or water can power these generators.