Magnetics Business & Technology - Winter 2017 - 11

FEATURE ARTICLE
north pole, the bar magnet in my figure is flipped and the tip of the
arrow in the compass is now a south pole. This approach works, too;
the only difference is that all polarities are reversed compared to
the first definition.
In practice, we occasionally interact with people who use the second definition, and who may not be sensitive to our two different
definitions of polarity. (One might say we are polar opposites.) It
can cause some confusion at first, until we recognize the source of
the mix-up. Once it is clear how the poles are defined, there should
be no problems, again as long as we are consistent.
My undergraduate textbook on electricity and magnetism offers
a third way to handle the conundrum. Authors Corson and Lorrain
claim the whole concept of magnetic poles is completely fictitious.
The only thing that really matters is magnetic flux. As someone who
learned about magnetic poles in the first grade, I puzzled over this
comment a long time before I could accept it. However, my acceptance was temporary, just for the duration of the course. Perhaps
this is the most elegant way to handle the question of polarity, to
say that the whole concept is unnecessary. However, this approach
could prove difficult to explain to customers, who likely believe in
poles!
So, we now have eighteen documented mistakes. Does anyone
have number 19?
About the Author - Dr. Stan Trout has more than 40 years' experience in the
permanent magnet and rare earth industries. Dr. Trout has a B.S. in Physics
from Lafayette College and a Ph.D. in Metallurgy and Materials Science from
the University of Pennsylvania. Stan is a contributing columnist for Magnetics Business & Technology magazine. Spontaneous Materials, his consultancy,
provides practical solutions in magnetic materials, the rare earths, technical
training and technical writing. He can be reached at strout@ieee.org.

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