ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
The law previously stated regarding the attraction and repulsion
of charged bodies may also be applied to magnetism if the pole
is considered as a charge. The north pole of a magnet will
always be attracted to the south pole of another magnet and will
show a repulsion to a north pole. The law for magnetic poles
is: Like poles repel, unlike poles attract.
(2) The Earth's Magnetic Poles. The fact that a compass
needle always aligns itself in a particular direction,
regardless of its location on earth, indicates that the earth is
a huge natural magnet. The distribution of the magnetic force
about the earth is the same as that which might be produced by a
giant bar magnet running through the center of the earth. The
magnetic axis of the earth is located about 150 from its
geographical axis thereby locating the magnetic poles some
distance from the geographical poles. The ability of the "north
pole" of the compass needle to point toward the north
geographical pole is due to the presence of the magnetic pole
nearby. The magnetic pole is named the "Magnetic North Pole".
However, in actuality, it must have the polarity of a magnet's
"south pole" since it attracts the north pole of a compass
needle. The reason for this conflict in terminology can be
traced to the early users of the compass. Knowing little about
magnetic effects, they. called the end of the compass needle
that pointed towards the north geographical pole, the "north
pole" of a compass. With our present knowledge of magnetism, we
know the "north pole" of a compass needle (a small bar magnet)
can be attracted only by an unlike magnetic pole, that is a pole
with the same magnetic polarity as the "south pole" of a magnet.
In reality, the "north pole" of a magnet is a northseeking pole.
c. Theories of Magnetism.
(1) Weber's Theory. A popular theory of magnetism considers
the molecular alignment of the materials. This is known as
Weber's Theory. This theory assumes that all magnetic
substances are composed of tiny molecular magnets. Any
unmagnetized material has had the magnetic forces of its
molecular magnets neutralized by adjacent molecular magnets,
thereby eliminating any magnetic effect. A magnetized material
will have most of its molecular magnets lined up so that the
north pole of each molecule points in one direction and the
south pole faces the opposite direction. A
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