What are Magnet Poles?
Magnet poles are simply places on a magnet where the field points strongly inward or outward. A uniformly magnetized bar magnet has one south pole and one north pole. As a matter of naming convention,
- North poles are where the field points outward.
- South poles are where the field points inward.
Also notice that the field points outward and inward to some extent along the sides of the magnet. There is no strict mathematical definition of exactly what a pole is. It is a term that refers to places on the magnet where the field strength is large.
Why are poles called North and South?
As it turns out, the magnetic field on the earth is not what most people expect.
- The field points inward near the geographic north pole.
- The field points outward near the geographic south pole.
What does this mean?
- The Arctic region of the earth is a magnetic south pole.
- The Antarctic region of the earth is a magnetic south pole
Magnets on the surface of the earth can be aligned by the earth's magnetic field. This is how a compass works.
- A magnet's north pole is attracted to geographic north.
- A magnet's south pole is attracted to geographic south.
Magnet poles which wanted to point to geographic north were called "north-seeking poles" which was shortened to "north" poles.
We now understand that poles are defined by the direction the magnetic field is pointing. Had magnet poles been named after we understood this, we might have named them "outward" poles and "inward" poles rather than north and south.
It is possible for a magnet to have several poles. For some sensor applications, it is sometimes useful to have ring magnets that have a series of alternating north and south poles.
Note that all magnets must have at least one north pole and at least one south pole. It is not possible to construct a bar magnet with only one pole.
The easiest way to determine which pole of a bar magnet is the north pole is to use a magnetic meter. If you do not have a meter, there are two other ways to do it.
- If you suspend a magnet from a string (or put it onto a floating object in water), the earth's magnetic field will rotate the magnet. The north pole of the magnet will point north.
- You can use a compass to determine which pole is which on a magnet. However, the compass will read backwards. Remember that the compass needle is a magnet. The pole of the compass labeled "North" is a north pole. It will be attracted to the south pole of the magnet!