Exploring Electrical Technology
IDST 300
Messiah College
Dr. Harold Underwood
Notes on the video: Earth's Magnetic Field
1. In 1269 A.D., Petrus Peregrinus noticed the orientation of iron filings around
a round piece of lodestone. He identified the __________of a magnet.
2. Around 1600, William Gilbert concluded that the earth is a huge __________. The
earth's arctic pole is considered the _______ pole of a __________.
Discussion Questions:
1. What did Gilbert discover about a heated magnet? Why significance does this have?
2. What term describes the difference between the geographic and magnetic north poles?
Why can this be especially important for Northern Canadians? According to this video,
what discovery by Columbus is not so well known? Why?
3. How would you describe magnetic inclination? Where is it most and least a problem?
Why?
4. Is a magnetic compass adequate for modern navigation? Why or why not?
Beyond the video:
1. For more about motion of magnetic north, see also the on-line articles:
Oregon State University. “Movement of North Magnetic Pole is accelerating.” 9 Dec.
2005. Space and Earth Science. 27 Jan. 2006 <http://www.physorg.com/news8917.html>.
Phillips, Tony. Earth’s Inconstant Magnetic Field. 29 Dec. 2003. Science@NASA. 27
Jan. 2006 <http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm>.
2. How lodestone may have been created: http://www.phy6.org/earthmag/lodeston.htm
3. What is GPS and how does it overcome problems with navigation by compass?