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#5.     Magnetic Field Lines

  (Files in red–history)


3. Aurora

   3H. Birkeland 1895

4. Electrons

    4H. Thomson, 1896

4a. Electric Fluid

5. Field Lines

    5H. Faraday 1846

6. EM Waves

7. Plasma

7a. Fluorescent lamp

    7H. Langmuir, 1927

Not so in space, however, where magnetic field lines are fundamental to the way free electrons and ions move. These electrically charged particles tend to become attached to the field lines on which they reside, spiralling around them while sliding along them, like beads on a wire (drawing below).

Because of this attachment, the behavior of electrified gas ("plasma") in space, a gas of free ions and electrons, is dictated by the structure of field lines: Electric currents, for instance, find it easiest to flow along such lines. Indeed, the role of field lines in a plasma resembles that of grain in wood: just as the grain is the "easy" direction along which wood splits most readily, so the direction of field lines is the one along which particles, electric currents, heat and certain types of waves prefer to flow.

Exploring further

A small bar magnet, on gimbals that allow it to point in any direction in space, can be procured from its manufacturer, Cochranes of Oxford, Ltd., Leafield, Oxford OX8 5NT, England. Two types are available, Mark 1 with jewelled bearings for $36.60, Mark 2 with simple bearings for $12.65. For details see their web site: (scroll down to "Magnaprobe").

Questions from Users:
            ***     Magnetic field lines
                  ***     Magnets of different shapes

Next Stop: #5H.  Field Lines--History

Last updated 25 November 2001
Re-formatted 9-28-2004