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Magnetism : Centuries ago, it was discovered that
certain types of mineral rock possessed unusual properties
of attraction to the metal iron. One particular mineral,
called lodestone, or magnetite, is found
mentioned in very old historical records (about 2500 years
ago in Europe, and much earlier in the Far East) as a
subject of curiosity. Later, it was employed in the aid of
navigation, as it was found that a piece of this unusual
rock would tend to orient itself in a north-south direction
if left free to rotate (suspended on a string or on a float
in water). A scientific study undertaken in 1269 by Peter
Peregrinus revealed that steel could be similarly "charged"
with this unusual property after being rubbed against one of
the "poles" of a piece of lodestone.
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Electromagnetism : The discovery of the relationship between
magnetism and electricity was, like so many other scientific
discoveries, stumbled upon almost by accident. The Danish
physicist Hans Christian Oersted was lecturing one day in
1820 on the possibility of electricity and magnetism
being related to one another, and in the process
demonstrated it conclusively by experiment in front of his
whole class! By passing an electric current through a metal
wire suspended above a magnetic compass, Oersted was able to
produce a definite motion of the compass needle in response
to the current. What began as conjecture at the start of the
class session was confirmed as fact at the end. Needless to
say, Oersted had to revise his lecture notes for future
classes! His serendipitous discovery paved the way for a
whole new branch of science: electromagnetics.
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