Magnetic Principle
• The magnetism of substances originates from their internal microscopic structures. For ferromagnetic materials like iron, cobalt, and nickel, they are composed of millions of tiny "small magnets" (magnetic domains) inside. When not magnetized, the directions of these magnetic domains are random, and their magnetic properties cancel each other out, so the whole object shows no magnetic performance. However, when encountering an external magnetic field, these magnetic domains will be rearranged in the same direction, and their magnetic properties will be superimposed, thus making the object show macroscopic magnetism and be attracted by magnets.
• However, copper and aluminum are not ferromagnetic materials. Inside their atoms, although electrons are also in constant motion (electrons revolve around the atomic nucleus and electron spin), which can generate magnetism, the directions of the electrons' movements are chaotic, and these magnetic effects cancel each other out. Therefore, under normal circumstances, they have no magnetism and will not be attracted by high-performance magnets.
Comparison with Other Metals
• Taking iron as an example, it is a typical ferromagnetic material. When iron approaches a high-performance magnet, the magnetic field of the magnet will make the magnetic domains inside the iron be arranged neatly, and then an attractive force will be generated. However, copper and aluminum do not have a magnetic domain structure that can be easily rearranged like iron inside, so they will not be attracted by high-performance magnets. For example, in daily experiments, when iron, copper, and aluminum are respectively placed close to a strong magnet, it will be found that iron is attracted while copper and aluminum show no reaction.
