MAGNETISM

1. 1 MAGNETISM

2. 2 Describe magnetism

3. 3 Magnetism is the force of attraction or repulsion due to electron motion.

4. Magnets have two poles, a north pole and a south pole. • Unlike magnetic poles attract each other, while likemagnetic poles repel each other. 4

5. 5 • Groups of atoms with magnetic poles aligned are called magnetic domains. • Materials with most of the domains lined up are considered magnetized.

8. The more domains that are aligned, the stronger the magnetic field in the material. 6

9. 7 Magnetic Field lines were introduced by Michael faraday , who named them ‘’lines of force.’’ Sketch this one

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11. 9 Permanent Magnets • A magnet made from materials that keeps its magnetism for a long time is a Permanent Magnets. • Examples are refrigerator magnets and neodymium magnets

12. 10 Temporary Magnets • Materials that become magnetized for a short time. • Temporary Magnets can be magnetized by rubbing the material in one direction. • Paper Clips are examples of temporary Magnets

13. 11 Magnetic Materials • Ferromagnetic Materials have strong magnetic properties. Examples are iron, nickel, and cobalt • Ferrous Metals are alloys, a mix of different metals. Iron is a part of this mix. • Both Ferromagnetic Materials and Ferrous Metals are attracted to magnets.

14. Magnetism From ElectricityA connection between electricity and magnetism was discovered (accidentally) over 100 years ago, it was noticed that a compass needle is deflected when brought into the vicinity of a current carrying wire. Thus, currents can induce a magnetic field. An electromagnet is simply a coil of wires which, when a current is passed through, generate a magnetic field, as below. 12 Current gives rise to magnetic fields, just as electric charge gave rise to electric fields Electromagnet

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16. 14 Electromagnets Electricity through the coiled wire creates a magnetic field which induces magnetism in the iron core. The domains in the core become aligned with the magnetic field of the coil. The more coils, the stronger the magnet.

17. A rotatingelectromagnet is used in an electric motor to convert electrical energy to mechanical energy. 15

18. 16 When a magnet is movednear a wire, an electric current can be created. This process is called electromagnetic induction. Electromagnetic induction is used in the operation of a generator, a device that converts mechanical energy to electrical energy. In a generator, an electric current is produced when a coil of wire is rotated in a magnetic field.

19. Generating electricity: • coil of wire rotated in a magnetic field • magnet is movednear a wire

20. The use of magnetic waves to make pictures of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces two-dimensional and three-dimensional pictures. July 3, 1977

21. Which of these correctly identifies both devices illustrated? APicture A: electric generator; Picture B:electromagnet BPicture A: electromagnet; Picture B: electric motor CPicture A: electric motor; Picture B: electromagnet DPicture A: electric generator; Picture B: electric motor

22. A magnetic field can be found in which of the following? A electric motor B sound wave C plastic cord D glass rod

23. 19 Properties of Magnets • If a magnet is cut in half, you will have two magnets, each with a north and south pole. • Forcefully hitting or dropping a permeant magnet can cause the domain to unaligned. This causes the magnet will lose its magnetism, become unmagnified. • Similarly, heating a magnet will also destroy its magnetism.

24. TOTD • What is magnetism? • Draw the domains of an un-magnetized material. • Draw the domains of a magnetized material. • What’s the difference between a permanent magnet and a temporary magnet? • What will happen if a magnet is cut in half • List 2 ways to destroy a magnet.