Any magnet has a north and a south pole.We know that the earth is a huge, although weak, magnet. In the figure, the end of the lodestone that points toward the

North Star is called its north-seeking pole; the opposite end of the lodestone is called its south-seeking pole. It is a basic law of magnetism that like poles repel each other and unlike poles attract each other.

For example, a pair of north poles repel each other and a pair of south poles repel each other, but a
north pole attracts a south pole.

Magnetic forces are invisible, but it is helpful to represent magnetic forces as imaginary lines. For example, we represent the earth’s magnetism as shown in the figure. There are several important facts to be observed in this diagram.

Since the north pole of a compass needle points toward the earth’s geographical North Pole, we recognize
that the earth’s geographical North Pole has a magnetic south polarity. In other words, the north pole of a compass needle is attracted by magnetic south polarity.

Another important fact shown is the location of the earth’s magnetic poles with respect to its geographic poles. The earth’s magnetic poles are located some distance away from its geographic

Still another fact to be observed is that magnetic force lines have a direction, which can be indicated by arrows. Magnetic force lines are always directed out of the north pole of a magnet and directed into the south pole.

Moreover, magnetic force lines are continuous; the lines always form closed paths. Thus, the earth’s magnetic force lines are continuous through the earth and around the outside of the earth.

The actual source of the earth’s magnetism is still being debated by physicists. However, insofar as compass action is concerned, we may imagine that the earth contains a long lodestone along its axis.

In turn, this imaginary lodestone will have its south pole near the earth’s north geographic pole; the imaginary lodestone will have its north pole near the earth’s south geographic pole.

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