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MAGNETISM

Explore the fascinating history of magnetism, from its discovery by the Chinese to its use by magicians and sailors. Learn about magnetic substances, how magnets attract or repel, and the important role of magnetic fields. Discover the origins of magnetism in matter and how to magnetize an object.

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MAGNETISM

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  1. MAGNETISM

  2. History of Magnetism • Discovered by the Chinese • Used by magicians and sailors • Illusions….. • Magnetic Hill, New Brunswick • Bermuda Triangle

  3. Categories of Substances • Three Categories • Magnetic • Ferromagnetic • Non-magnetic

  4. Magnetic Attract or repel • Object that has a field and that can attract some other objects. • Example: horseshoe magnet Invisible fields

  5. Ferromagnetic Not a magnet • Is attracted by a magnet • Can be magnetized • Must contain iron, nickel or cobalt • eg: paper clip or nail

  6. Non-Magnetic • Is not attracted by a magnet • Example: glass, plastic, or wood

  7. Important Facts about Magnets Facts: • All magnets have two poles, a North (N) and a South (S). They are known as dipoles. • Fields are infinite in size & 3-Dimensional • Similar poles repel & opposite poles attract. Repulsion Attraction

  8. Poles N attracts South S attracts North N repels North S repels South Opposites attract Likes repel

  9. Mapping Magnetic Fields • Remember • the lines never cross • Always goes from North to South • Closer the lines, stronger the attraction • Around a magnet there are lines of force that have direction and strength (magnetic field). S N

  10. N S N S Compass North end • The needle of the compass is magnetic • Red Tip of needle is North • Red Tip will always be attracted towards South S Tip of arrow Is North therefore It is attracted to South Example #1 Example #2

  11. Why the Compass Works Geographic North Geographic South

  12. N S Why the Compass Works Magnetic South Magnetic North

  13. Key Points to Remember • Magnetism is a property that makes certain material attract or repel. • Ferromagnetic • Attracted by magnet • Must contain Fe, Ni, Co • Nonmagnetic • Not attracted by magnet • Opposites attract (i.eN & S) • Likes Repel (i.e. S & S or N & N) • Magnetic Field • Arrows always go from north to south (outside magnet) • Lines of force never cross • The closer the lines, the stronger the field • Compass • Red portion of compass needle isNorth and is always attracted to South HINT Nerd to Sexy

  14. Origins of Magnetism of Matter • Scientists believe that magnetism comes from spinning electrons around the nucleus of the atom. • When atoms clump together they form a domain.

  15. Origins of Magnetism of Matter • Similar electron spins produce a strong domain, where as opposite electron spins cancel one another out and produce a weak domain. • If enough domains align in the same direction, this will create a magnetic field.

  16. How to Magnetize an Object • Bring the ferromagnetic substance in contact with another magnet. • Bang the ferromagnetic substance (example: striking a nail repeatedly). • Heat up the substance and cause the domains to align. • Run electric current through the ferromagnetic substance. • Please note that all of these methods can also de-magnetize a magnet.

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