Physics Lesson 16.1.2 - Magnetic Field of Magnets and Earth. Magnetic Poles

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Welcome to our Physics lesson on Magnetic Field of Magnets and Earth. Magnetic Poles, this is the second 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.

Magnetic Field of Magnets and Earth. Magnetic Poles

By definition, magnetic field is the space around a magnet in which its attractive or repulsive effect is observed. As you see, the definition of magnetic field is very similar to those of other fields (gravitational and electric) we have discussed earlier.

A magnet behaves in opposite way when approaching a magnetic material in two opposite positions. For example, if we bring one end of a bar magnet near an iron nail the magnet attracts the nail while if we bring the other end of the magnet near the same iron nail, the magnet repels it. These two extremities are known as magnetic poles. To make distinction between poles, we call them North and South poles respectively. The North pole is coloured in red while the South pole in blue, as shown in the figure below.

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

The general law governing the interaction of magnets is similar to that of electric charges, i.e.:

"Like poles repel each other while unlike poles attract each other."

The interaction between magnets is an indicator for the existence of the magnetic force - a force that causes attraction or repulsion between poles as in the law discussed above.

The reason why magnetic poles are named North and South is because when a bar magnet like the one shown below is suspended using a thread, it will align in the North-South direction of the Earth after it stops swinging (when the equilibrium is reached).

Therefore, the magnetic pole pointing towards the geographic North Pole is the South Pole of magnet. However, sometimes it is called the North seeking pole as it point towards the North Pole of Earth. The same for the North Pole of magnet as well. Therefore, one must be careful to avoid confusion.

The reason why this alignment occurs is the existence of a magnetic field produced by the Earth. Indeed, Earth is a giant magnet producing its natural magnetic field. As a result, one of the seven layers of atmosphere known as magnetosphere does exist. It is the outmost layer of atmosphere. It is very crucial in repelling the hazardous cosmic rays coming from all parts of the universe. Therefore, magnetosphere is irreplaceable in terms of the continuity of life on earth despite the fact it does not contain any air.

You have reached the end of Physics lesson 16.1.2 Magnetic Field of Magnets and Earth. Magnetic 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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