Magnetism

Cow magnet

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Magnets

   Video: History Channel, Modern Marvels: Magnets.  About 44 minutes          

Synopsis

 "Magnets" reveals the essential role magnets play in today's society - from powering high-speed trains and theme-park rides to generating electricity and creating mechanical power, and also providing the basis for computers and data storage.

The video begins by demonstrating how linear synchronous motors (change polarity in sync with the motion of a vehicle) work and allow a theme-park ride to reach 100 mph in 7 seconds, and maglev trains speeding 270 mph.

Viewers also see iron filings used to reveal magnetic lines of force, and electromagnets used to separate materials in a junk yard. Then its on to an understanding of how electromagnets are built and operated, followed by the creation of more mundane "refrigerator" magnets.

How the earth's magnetic field shields us from lethal cosmic bombardment is explained.

Man's awareness of magnetism began about 2,000 years ago when the Greeks and Chinese both discovered lodestones (magnetite); today's experts believe its magnetism is created by lightning strikes. Generating electricity and then power from the electricity are key to man's current standard of living.

Various alloys have been found to make stronger magnets; rare-earth magnets help create miniature disc drives for today's laptops. The strongest magnetic field is a neutron star - up to 1,000 trillion times that of earth.

Researchers are now looking at plastic magnets whose strength can be altered with various colors of laser light. NASA is also hopeful that magnet fields can be used to contain the hot gases created by plasma propulsion, thus lowering considerably the costs of space travel.