Main Difference – North vs. South Pole
Magnets are objects that can either attract or repel other magnets. They can also attract magnetic materials (e.g. iron) that are not themselves magnets. A magnet always comes with two poles: a north pole and a south pole. The main difference between north and south pole is that a north pole is attracted towards the south pole of another magnet while a south pole is attracted towards the north pole of another magnet.
The North and South Poles
Every magnet has two poles. One end forms the “north pole” while the other end forms the “south pole”. When two like poles (north-north or south-south) are brought together, they repel. When two unlike poles (north-south) are brought together, they attract. If a magnet is hung and allowed to rotate freely, it can align itself so that the “north pole” of the magnet points towards The Earth’s “North Pole” (The Arctic). However, since it is the opposite poles that attract, if we consider The Earth, the “south pole of the Earth’s magnet” is at the “North Pole” (The Arctic) and vice versa. This is depicted below:
The Earth’s magnetic field
The Earth’s magnetic field is thought to have been formed by the movement of molten iron in The Earth’s core. In the above diagram, note that the magnetic poles are at a small deviation from the geographic poles. When compasses are used for navigation purposes, it is important to account for this difference. The deviation is always changing. The deviation (in degrees) between the geographic and magnetic poles for 2015 are shown below (as modeled by US/UK World Magnetic Model):
Magnetic declination for 2015 (National Centers For Environmental Information, USA)
On the map, deviations are marked in degrees. Note that a positive angle denotes a declination to the east from the geographic north, while a negative angle denotes a declination to the west from the geographic north.
Poles and the Magnetic Fields
Each magnet has two poles. Magnets with only one type of pole (called “magnetic monopoles”) have never been observed. If you cut a bar magnet in half, the resulting halves will each end up with both north and south poles. The idea that magnets always form two poles is embedded in Gauss’s law of magnetism, which can be expressed as:
This law expresses that for any closed surface, the total magnetic flux entering the surface is equal to the total magnetic flux leaving it. This is only possible if the (imaginary) magnetic field lines form closed loops. For this to happen, a north pole must always be accompanied by a south pole. This is in contrast to electric charges, which can exist by themselves. There are some theories that allow for magnetic monopoles but they have never been observed and none of these theories have been confirmed.
Magnetic field lines are always drawn with arrowheads pointing towards the south poles. North poles are considered the “sources” of the magnetic field lines while the south poles are considered “sinks” of magnetic field lines.
Difference Between North and South Pole
Behaviour around another Magnet
North poles are attracted by south poles of other magnets while they are repelled by north poles of other magnets.
South poles are attracted by north poles of other magnets while they are repelled by south poles of other magnets.
Orientation when allowed to rotate freely
North pole of a magnet ends up pointing towards the “North Pole” of The Earth.
South pole of a magnet ends up pointing towards the “South Pole” of The Earth.
Direction of Magnetic Field Lines
North poles are sources of magnetic field lines.
South poles are sinks of magnetic field lines.
Colour Representation
Often, the north pole of a magnet is shown in red while the south pole is shown in blue.
Image Courtesy
“This diagram shows the magnetic field of our Earth” by Alexyjoy (Own work) [CC BY-SA 3.0], via Wikimedia Commons
“US/UK World Magnetic Model – Epoch 2015.0 Main Field Declination (D)” by NOAA National Centers for Environmental Information (NCEI) [Public Domain], via ngdc.noaa.gov
