Physics Lesson 16.1.6 - The Earth as a Giant Magnet. Two North Poles.

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Welcome to our Physics lesson on The Earth as a Giant Magnet. Two North Poles., this is the sixth lesson of our suite of physics lessons covering the topic of Introduction to Magnetism, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

The Earth as a Giant Magnet. Two North Poles.

We explained at the beginning of this tutorial that a bar magnet suspended in a thread points towards the two geographic poles. This is the reason why we use the terms North and South to describe the poles of a magnet. In addition, we explained that such a behaviour of bar magnets indicates the existence of Earth magnetic field, which determines the orientation of bar magnets in space.

Indeed, Earth is considered as a giant magnet containing its own magnetic field, whose lines as shown in the figure below.

Physics Tutorials: This image provides visual information for the physics tutorial Introduction to Magnetism

In fact, magnetic and geographic poles do not lie exactly in the same direction; they diverge from each other by an angle of about 220. This means when a traveller starts moving from equator in the direction of North Pole indicated by the magnet, he will not reach the geographic North Pole but he will instead end his motion about 2000 km away from it. In other words, if a person starts travelling from Africa towards the North Pole indicated by the suspended bar magnet, he will end his travel at north of Canada, not at the North Pole of the Earth. That's why there exist two distinct North Poles: one geographic and the other magnetic.

The device used from travellers to orient themselves - especially when sailing in oceans, during which it is very difficult to know the direction as no land is visible - is called compass. It consists on a small magnetic needle placed on a thin pin, parallel to a circular case in which the main directions are written.

The Earth's magnetic field is similar to that of a bar magnet extending from the North to the South magnetic pole. This means the magnetic field lines near the poles are vertical while in other positions they are parallel to the Earth surface, i.e. they are horizontal.

You have reached the end of Physics lesson 16.1.6 The Earth as a Giant Magnet. Two North Poles.. There are 9 lessons in this physics tutorial covering Introduction to Magnetism, you can access all the lessons from this tutorial below.

More Introduction to Magnetism Lessons and Learning Resources

Magnetism Learning Material
Tutorial ID	Physics Tutorial Title	Revision Notes	Revision Questions
16.1	Introduction to Magnetism
Lesson ID	Physics Lesson Title	Lesson	Video Lesson
16.1.1	A Brief History of Magnetism. Natural and Artificial Magnets
16.1.2	Magnetic Field of Magnets and Earth. Magnetic Poles
16.1.3	Magnetic Field Lines
16.1.4	How is a Magnet Produced?
16.1.5	Permanent and Temporary Magnets
16.1.6	The Earth as a Giant Magnet. Two North Poles.
16.1.7	Magnetosphere
16.1.8	Magnetism in Animals
16.1.9	Magnetism in Use

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