In simple terms, magnetism is the effect of magnetic force when a substance is placed in an inhomogeneous magnetic field. In the same inhomogeneous magnetic field, the strength and magnetic strength of the material are determined by the direction and intensity of the magnetic force per unit mass of material. Because any material is magnetic, any material is subjected to magnetic forces in a non-uniform magnetic field.
What really exists in the space around the magnetic pole is not a magnetic field, but a field, which we call a magnetic field. The mutual attraction of magnetic substances is performed by a magnetic field. We know that there is gravitation between materials, it is a kind of gravitational field. A magnetic field is similar to a field that covers the space around a magnetic pole. The strength of the magnetic field can be expressed by the number of imaginary lines of magnetic force, where the magnetic field is strong and the magnetic field is weak. The number of magnetic lines passing through a unit section is called the magnetic flux density.
The charged particles of the motion are subjected to a kind of Lorentz force in the magnetic field. The magnetic field intensity is determined by the amount of Lorentz magnetic force that the same charged particles receive in different magnetic fields. Tesla is an international system of units for magnetic flux density. Magnetic flux density is a basic physical quantity that describes a magnetic field, and magnetic field strength is an auxiliary quantity that describes a magnetic field. Tesla (N) (1886~1943) was a Croatian-American electrical engineer who had invented transformers and AC motors.
The magnetic properties of materials are not only ubiquitous but also diverse, and have therefore been extensively studied and applied. From our bodies and surrounding matter, as far as all kinds of stars and interstellar matter, the microscopic world's atoms, atomic nuclei and elementary particles, and various materials of the macro-world, all have magnetic properties of one kind or another.