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Some irons, when dug up,
attract other metals.
They are called MAGNETS.
The reason that they are
magnetic is that their
DOMAINS are aligned.
One end of a bar magnet
is the NORTH POLE, the
other end the SOUTH
POLE.
A rule of magnetism is
that LIKE POLES REPEL,
UNLIKE POLES ATTRACT.
North attracts South and
repels North etc.
The North pointer on a
compass is actually a
South pole since it is
attracted by the North
pole of the earth.
A magnet is surrounded
by an invisible MAGNETIC
FIELD made of magnetic
LINES OF FORCE.
These lines of force can
be made visible by
covering a magnet with a
sheet of paper and
sprinkling iron filings
on the paper.
The lines of force run
from north to south.
Lines of force pass
through all materials
including insulators.
They pass through some
more easily than
others. These are said
to have a lower
RELUCTANCE. Iron
has a lower reluctance
than air.
The lines of force
prefer to pass through
lower reluctance
materials.
PERMANENT magnets are
made of steel or steel
alloys. Brass, copper
and aluminum do not
magnetize.
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