MAGNETISM

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

Categories of Substances Three Categories Magnetic Ferromagnetic Non-magnetic

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

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

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

Important Facts about Magnets 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

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

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

Compass S N S N S The needle of the compass is magnetic 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 N S Example #1 N S Example #2

Why the Compass Works Geographic North Geographic South

Why the Compass Works Magnetic South N S Magnetic North

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.e N & 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 is North and is always attracted to South HINT Nerd to Sexy

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.

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.

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.