Magnets can attract iron, but why can gravitational attraction attract anything?

Electromagnetic force and gravitational force are two forces of different nature, which are destined to act on different objects.

In physics, all "forces" can be classified into four major interactions, and all the real "forces" encountered in our lives, except for gravity, are essentially electromagnetic interactions, such as friction, tension, elasticity, pressure, and so on.

Electromagnetic force. Magnetism is also an electromagnetic interaction in nature, which can be described by Maxwell's equations, and the reason why magnets can attract metals such as iron, cobalt, and nickel is because these substances are ferromagnetic substances.

Principle: 1) We know that common substances are almost always composed of atoms;

2) Electrons outside the nucleus move around the nucleus, so the moving charge generates a magnetic field, and some substances will have a situation where the net magnetic moment of a single atom is not zero;

3) In general, the internal magnetic moment of the substance is irregularly arranged, resulting in zero magnetic moment of the substance as a whole;

4) But in the case of ferromagnetic substances, there will be interactions between adjacent atoms, and then many adjacent atoms form "magnetic domains", each ranging from a few microns to a few millimeters, like a small magnetic needle;

5) These large and small magnetic domains are random in direction without external force, and the whole is not magnetic; Once there is an external magnetic field, these magnetic domains seem to be commanded, the magnetic moment is biased in the same direction, and then the whole becomes magnetic, attracted by the magnet;

6) When the external magnetic field is removed, the direction of the magnetic moment of some magnetic domains may not be restored, so the whole shows weak magnetism, so we say that the iron is magnetized;

7) When the ferromagnetic substance is heated, the thermal motion of the molecule becomes violent, when the kinetic energy of the thermal motion is greater than the action energy between adjacent atoms, the ferromagnetic substance will be transformed into a paramagnetic substance, and the response to the external magnetic field is weak, which is no longer attracted by the magnet, and this critical temperature is called the "Curie point";

For example, at the bottom of the rice cooker at home, there is a ferromagnetic substance, the Curie point is generally 103, when the water in the pot is boiled dry, the temperature in the pot rises to 103, the substance is no longer attracted by the electromagnet to produce action, so as to disconnect the heating power.

Universal gravitation. In classical mechanics, the magnitude of gravitational force depends on the distance and mass of matter, which is the famous law of gravitation, which also shows that mass matter will produce gravitational force.

Magnets attract iron, gravitational attraction attracts everything, because motion creates a magnetic field, and there is also an interaction between these two substances, and almost all matter produces gravity.

The attraction between magnets is magnetic, and the magnetism is not the same as the object of gravity, and there is a gravitational force in any object in the world, but the magnetic force must have a magnet to be generated.

This is the mystery of the universe, almost everything in the world has gravity, making the whole universe more like a whole.

Because gravitational force has nothing to do with the material of the object, but has to do with mass, gravitational force can attract anything.

1. There are only a few metals that can be attracted by magnets, such as iron, nickel, cobalt and other magnetophilic metals. Most other metals such as gold, silver, copper, aluminum, tin, lead, titanium, etc., are not attracted to magnets.

2. The composition of the magnet is iron, cobalt, nickel and other atoms, and the internal structure of the atoms is relatively special, and it has a magnetic moment.

Magnets are able to attract ferrous substances such as iron, nickel, cobalt, and other metallic substances. When a magnet is brought close to these substances, it creates a magnetic force on them, causing them to be adsorbed on the magnet. This is because magnets are magnetic and can generate a magnetic field within a certain range, causing a change in the magnetic moment of electrons inside substances such as iron, nickel, and cobalt, resulting in an attractive force.

In addition to the above-mentioned ferrous substances, magnets can also attract some other substances such as ferrite, NdFeB, magnetic liquids, etc. These substances are also magnetic and can be adsorbed by magnets. In addition, magnets can also have an impact on some currents, electrons, ions, etc., such as electromagnets, which use the magnetic field generated by electric currents to achieve adsorption and control of objects.

Aluminum strip coil winding magnet.