Magnetic Force

Magnetic

What is magnetism? We call the property that objects can attract iron, cobalt, nickel and other substances called magnetism. Since magnetism refers to a property of a magnet to attract paramagnetic substances, it is determined by the properties of the magnet itself. Magnetic force is a kind of interaction force. There is no magnetic force in the magnet itself. It is the result of the interaction between two magnets, which can be expressed as repulsion and attraction. Therefore, it can only be said that the two poles of the magnet are the most magnetic", but it cannot be said that "the two poles of the magnet are the most magnetic". When talking about the properties of magnets, we must say magnetism, and when it comes to the interaction between magnets, we should say magnetic force.

Magnets and Magnetic Fields

Magnet

Magnet, as its name implies, refers to a magnetic object, which can be a magnetic source or a magnetic conductor, such as a ferrite magnet with two poles plus an iron plate, and the magnetic field will concentrate on the edge of the iron plate. It has such an invisible force that it can both suck in some things and push some things out. The force exerted by a magnet to attract or repel an object is called the magnetic force. Since the magnetic force is a force, it has a size, and the size of the magnetic force has an inseparable relationship with the magnet itself.

Causes of magnetism:

1. Permanent magnet

2. Electromagnetically

If an electric current is passed through a straight metal wire, a circular magnetic field will be created in the space around the wire. The greater the current flowing through the wire, the stronger the magnetic field produced. The magnetic field forms a circle around the wire. The direction of the magnetic field can be determined according to the "Right Hand Rule": extend the thumb of the right hand, and bend the remaining four fingers together towards the palm. At this time, the direction of the thumb is the direction of the current, and the direction of the other four fingers is the direction of the magnetic field. In effect, the magnetic field produced by this straight wire is similar to the effect of placing a ring of small magnets around the wire with NS poles end-to-end.

If a long metal wire is wound in one direction on a hollow cylinder, the formed object is called a solenoid. If you energize this solenoid, what happens? When energized, each turn of the solenoid generates a magnetic field. Then, at the position between two adjacent turns, the total magnetic field cancels out due to the opposite direction of the magnetic field; while inside and outside the solenoid, the magnetic fields generated by each turn of the coil are superimposed on each other. It can also be seen that the shape of the magnetic field outside the solenoid is the same as that produced by a magnet. The magnetic field inside the solenoid just forms a closed magnetic field line with the external magnetic field.

3.       Flowing liquid metal. Causes of magnetism, in addition to permanent magnets and electromagnetism. Scientists have found that flowing metal can generate a strong magnetic field. Some scientists have done experiments: pouring molten iron into a sphere and making the sphere rotate, thereby generating a huge magnetic force. Based on this, it is speculated that there may be a liquid iron core inside the earth, and it is constantly rotating to form a magnetic field. It has also found a basis for the changes in the strength of the earth's magnetic field, and even the exchange that has occurred in the history of the North and South Pole.

Magnetic Field

Simple definition: A magnetic field exists in a space that can generate a magnetic force. Magnetic fields are a special kind of substance. There is a magnetic field around the magnet, and the changing electric field can also generate a magnetic field, and the interaction between the magnets is mediated by the magnetic field.

A magnet with closed magnetic field lines does not show a magnetic field to the outside, and only a magnet with open magnetic field lines shows a magnetic field to the outside. The magnetic field can be shielded by a magnetically conductive object. Once the magnetic field lines of the magnet are shielded and closed by the magnetic conductive body, the external magnetic field will be weakened, or the magnetic force will be lost.

A special form of matter that exists in space around an electric current, moving charge, magnet, or changing electric field. Since the magnetism of a magnet is derived from an electric current, which is the movement of electric charges, in general terms, a magnetic field is produced by a moving electric charge or a changing electric field.

The basic feature of a magnetic field is that it can exert a force on the moving charges in it. Modern theory, however, states that magnetism is a relativistic effect of electric field forces.

Similar to the electric field, the magnetic field is a vector field that is continuously distributed in a certain space area. The basic physical quantity describing the magnetic field is the magnetic induction intensity vector B , which can also be graphically represented by magnetic induction lines. However, as a vector field, a magnetic field behaves quite differently from an electric field. The magnetic field generated by the moving electric charge or the changing electric field, or the total magnetic field of the sum of the two, is a passive and rotating vector field, and the magnetic field lines are a closed family of curves that do not break or cross. In other words, in the magnetic field, there is no source that emits the magnetic field lines, nor does there exist a tail where the magnetic field lines converge. The closure of the magnetic field lines indicates that the loop integral along the magnetic field lines is not zero, that is, the magnetic field is a swirl field rather than a potential field (conservative field), no There are scalar functions like electric potential.

Magnetic induction intensity: The number of magnetic lines of force passing through a unit area perpendicular to the direction of the magnetic lines of force, also known as the density of magnetic lines of force, also known as magnetic flux density, expressed in B, and the unit is tesla (Sla) T.

Magnetic flux: The magnetic flux is the total number of magnetic lines of force passing through a certain cross-sectional area, represented by Φ, the unit is Weber (Weber), and the symbol is Wb. The expression of the magnetic flux passing through a coil is: Φ=B·S (where B is the magnetic induction intensity and S is the area of ​​the coil.) 1Wb=1T·m2

Magnetic field direction: It is stipulated that the direction of the magnetic field force on the north pole of the small magnetic needle at a certain point in the magnetic field is the direction of the electromagnetic field. Directions from the North Pole to the South Pole.

Magnetic field lines: Draw some curves in the magnetic field so that the tangent direction of any point on the curve is the same as the direction of the magnetic field at this point. These curves are called magnetic field lines. Magnetic field lines are closed curves. It is stipulated that the direction pointed by the north pole of the small magnetic needle is the direction of the magnetic field line. The magnetic field lines around the magnet all come out from the N pole and enter the S pole, and the magnetic field lines inside the magnet go from the S pole to the N pole.

The electromagnetic field is the medium of electromagnetic action, and it is a unified whole. The electric field and the magnetic field are its two sides that are closely related and interdependent. The changing electric field produces a magnetic field, the changing magnetic field produces an electric field, and the changing electromagnetic field propagates in space in the form of waves. . Electromagnetic waves propagate at a limited speed, have exchangeable energy and momentum, the interaction between electromagnetic waves and objects, the mutual transformation between electromagnetic waves and particles, etc., all prove that the electromagnetic field is an objectively existing substance, and its "special" is only that it has no static mass. .