The Earth has north and south geographic poles. If we could
draw a line between these two poles it would pass through the centre of the
Earth. It would also lie along the axis about which the Earth rotates.
The Earth acts like a giant magnet and so also have north
and south magnetic poles. The magnetic poles are not always in the same place.
At the moment the Earth`s south magnetic pole is about 1,900 km (1,180 miles)
away from the Earth`s geographic south pole. So there is more than one answer
to the question where is the Earth`s south pole...! An imaginary line drawn
between the Earth`s magnetic poles would not necessarily pass through the
centre of the Earth.
A compass needle points to the Earth`s magnetic poles. The
navigator wants to know his direction in relation to the geographic poles. So
he has to know the distance between the geographic and magnetic poles to
correct his compass reading.
A compass needle will only point north –south if
there are no other magnets near it. If there are, the needle will be attracted
towards them and will point in a different direction or be deflected. It was
discovered that if a compass was held near a wire carrying an electric current,
the needle was deflected. But if the current was switched off the needle swung
back and pointed north-south again. This meant that the current was acting like
a magnet. If some wire is wrapped around a magnet and a current passes through
the wire, the magnet will become much stronger. This is known as an
electromagnet.
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