The characteristics of the magnetic field
Magnetic field characteristics of bar magnet
As previously discussed, the change in energy within the volume of a magnetic field. The magnetic field of a bar magnet can reflect its magnetic field lines in a three-dimensional space. The magnetic field lines show the distribution of the magnetic field when it leaves one pole and enters another pole.
It can be seen in the image of the magnetic field lines that the magnetic poles are concentrated at both ends of the magnet. The area where the exit poles are concentrated is called the N pole of the magnet and the area where the entrance poles are concentrated is called the south (S) pole of the magnet.
Horseshoe-shaped magnetic field characteristics
Magnets come in various shapes and the more common one is a horseshoe (U) magnet. Horseshoe-shaped magnetic field lines have many important properties. The north and south poles of a magnet are like a bar magnet, but the magnet is bent so that the two poles are on the same plane. The magnetic field lines of the flow force from the south pole to the north pole are like a bar magnet. However, since the poles are closer together and there is a more direct path for the magnetic flux lines to travel between the poles, the magnetic field is concentrated between the poles.
If a bar magnet is placed across the end of a horseshoe magnet, or is formed as a ring-shaped magnet, the lines of magnetic force will not even need to enter the air. This type of magnet may be used in a limited way, in which the magnetic field is completely contained in the material. However, it is important to understand that the magnetic field can flow within the material in the loop.
General properties of magnetic field lines
Magnetic field lines have many important properties, including:
- They seek the path of least resistance between opposing magnetic poles. With a bar magnet to the right as shown, they try to form a closed loop from the south pole to the north pole.
- They never cross each other.
- They all have the same strength.
- Their density decreases (they spread out) as they move from an area with higher permeability to an area with lower air permeability.
- The density decreases as the distance from the magnetic pole increases.
- They are thought to have a direction as if they were flowing, although they did not actually move.
- They flow from the material from the South Pole to the North Pole and the air from the North Pole to the South Pole.