Why does breaking a magnet turn into two separate magnets?
First of all, it should be clear that after a long magnet is broken into two parts in the length direction, a pair of N and S poles will naturally be formed at the fracture, and the polarities of the two ends of the original magnet will remain unchanged. No matter how many parts are broken, the direction of the magnetic field lines inside the magnet remains unchanged, and the polarity will not change. So why can't the two halves of the magnet be attracted together at the fracture? The reason is that the fracture is not completely broken in the plane, and a complex curved surface will be formed, so that the magnetic field direction of the fracture is also a complex structure. In addition, the magnet is fractured by external force, and the local magnetic field at the fracture also changes. Therefore, the two magnets have a mutual attraction force and a larger lateral repulsion force, which is difficult to restore.
The magnetic field is not a plane, we are misled by the magnetic field diagram, in fact the magnetic field is three-dimensional! It's all over the place, so I'd say people in a two-dimensional world can't understand the wonders of a three-dimensional world (try finding a cube yourself and draw each side)! According to the length angle (up and down) of the magnetic strip, the latitude is attractive, and the others (front, back, left and right) are all repulsive. There are too many repulsive surfaces at the fracture and too few gravitational surfaces, so they repel each other.
The magnetism of a magnet is a macroscopic manifestation of the internal atomic magnetism, which originates from atomic angular momentum, that is, the superposition of spin angular momentum and orbital angular momentum. Magnets are generally made of ferromagnetic materials such as iron, cobalt, nickel or ferrite. Inside a ferromagnetic material, the angular momentum of atoms is oriented in the same direction in a region called a "magnetic domain". When the material is not magnetized, the angular momentum of atoms in different magnetic domains is randomly oriented, and the material does not show macroscopic magnetism as a whole; Large magnetic domain), the material shows macroscopic magnetism, and it is made into a magnet. In the finished magnet, the angular momentum orientation of all atoms is basically the same. The direction of the angular momentum is marked with an arrow. The direction the arrow points to is the N pole of the magnet on the macroscopic level, and the direction facing away from the arrow is the macroscopic S pole of the magnet.
Magnet cross-section and vertical section