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Magnets and Magnetism 8th grade science Properties of Magnets… 2000 years ago the Greeks discovered a mineral that attracted things made of iron. They named this mineral Magnetite because it was discovered in Turkey near the town call Magnesia. Magnet is any material that attracts iron or things made from iron. Magnetic Poles one of two points, such as the ends of a magnet, that have opposing magnetic qualities. Properties of Magnets… All magnets have a North and South Pole. One part of the magnet will always point to the North while the other will always point to the South. The poles of magnets are always in pairs. You will never find a magnet with just one pole. Magnetic Force is the force of attraction or repulsion generated by moving or spinning electric charges. Properties of Magnets… Magnetic field is the region around a magnet in which magnetic forces can act. The shape of a magnetic field can be seen below. The closer together the field lines are, the stronger the magnetic field is. The magnetic field is strongest at the poles The Cause of Magnetism Magnets can pick up things like paper clips and nails but why cant it pick up things like paper, plastic, pennies, or aluminum foil? Atoms and Domains… All matter is made of atoms. Electrons are the negatively charged particles of the atom. Electrons move around and make or induce a magnetic field. Materials like copper & aluminum aren’t magnetic because the individual atoms cancel each other out. Materials like iron, nickel, & cobalt have their atoms grouped in tiny areas called domains. These domains line up to make N. & S. poles. Losing Alignment If the domains in an object are randomly arranged, the magnetic fields of the individual domains cancel each other out, and the object has no magnetic properties. If most of the domains in an object are aligned the magnetic fields of the individual domains combine to make the whole object magnetic. Dropping or hitting a magnet can change the domains. Placing a magnet near a stronger magnet or increasing the temperature significantly will also change the magnetic properties. Making Magnets Magnets can be made from iron, cobalt, or nickel if you can simply line up the domains. An iron nail can be magnetized if you rub it in one direction with one pole of a magnet. Electric current can also be applied to metal causing it to become magnetized. Cutting a Magnet Would cutting a magnet in half leave you with a North Pole magnet and a separate South Pole magnet? If you cut a magnet into two separate pieces, each piece will still be a magnet with a North Pole and a South Pole. Kinds of Magnets Ferromagnets are magnets made from iron, cobalt, nickel, or mixtures of these metals. Electromagnets are magnets produced through the use of a strong electric current. The core of an electromagnet is usually made from iron. Earth as a Magnet Man has used a compass to find his way for thousands of years. A compass is simply a freely floating/spinning magnet. The painted portion of the needle on a compass is a North Pole magnet. A compass needle points North because the magnetic pole of Earth that is closest to the geographic North Pole is actually a magnetic south pole. Earth as a Magnet English physician William Gilbert said in 1600, “Earth behaves as if it has a bar magnet running through its center and the poles of this imaginary magnet are located near Earth’s geographic poles.” The Earth doesn’t really have a bar magnet running through it though. Scientist believe the Earth’s magnetic field is caused by movement of electric charges in Earth’s core. Earth’s inner core is made of iron and nickel and is under extreme pressure. The outer core is liquid and flows as the Earth rotates, which causes electric charges to build and create a magnetic field.