Unveiling the Characteristics of Electromagnetic Magnetic Lines of Force: An Introduction

Part 1 :  What is the electromagnetic force ?

The magnetic force of an electromagnet is the attraction of the magnetic field generated by the electromagnet to ferromagnetic materials. When an electric current passes through a solenoid coil wound around an iron core, a magnetic field is generated, which can attract magnetic materials such as iron, nickel, and cobalt. The magnitude of the magnetic force is related to factors such as the number of solenoid coil turns, the magnitude of the current, and the material of the iron core. For example, the more turns of the solenoid coil and the greater the current, the stronger the magnetic force of the electromagnet is usually. The magnetic field and electrostatic field of an electromagnet are all directional, and people generally use magnetic lines of force to outline the distribution of the magnetic field.

Part 2 : What is the magnetic lines of force  ?

The magnetic lines of force are virtual lines used to vividly describe the distribution of the magnetic field around the electromagnet/solenoid.The magnetic  lines of force are closed curves that cross each other. Outside the electromagnet, they start from the N pole (North Pole) and return to the S pole (South Pole), while inside, they point from the S pole to the N pole. The density of the magnetic field can indicate the strength of the magnetic field. The denser the magnetic lines of force, the stronger the magnetic field, and the sparser the magnetic field, the weaker the magnetic field. Just like the contour lines on the map are used to indicate the height of the terrain, the magnetic lines of force can help people intuitively understand the distribution and direction of the magnetic field.

Part 3 :  What are the characteristics of magnetic lines of force?

1. Magnetic lines of force describe the direction of the magnetic line of force that originates from a north pole at any given position.In the L part of the magnetic rib, they deviate from the N pole to the V pole, and in the magnetic field, they deviate from the S pole to the N pole.
2. The direction of the line break at any point on the magnetic line of force is the direction of the magnetic field at that point, that is, the direction of the N pole of the magnetic needle at that point.
3. The closeness of the magnetic lines of force of reflects the height of the magnetic field. The denser the magnetic lines of force, the stronger the magnetic field. In a uniform magnetic field, the magnetic lines of force are parallel to each other and evenly distributed.
4. The direction of the magnetic lines of force can be determined by Ampere's law, as follows:                                                                                                                                   Straight wire with current: Hold the straight wire with current in your right hand, let your thumb point to the direction of the current, and the direction of the magnetic lines of force around the straight wire with current pointed by the four fingers.                                                                                                                                                                    Energized solenoid: Hold the energized solenoid with your right hand, bend your four fingers in the same direction as the current, and the end pointed by your thumb is the N pole of the energized solenoid. Electromagnets are usually equivalent to energized solenoids, so the direction of their magnetic lines of force can be determined. Outside the electromagnet, the magnetic lines of force start from the N pole and return to the S pole, and inside it points from the S pole to the N pole.
5. The magnitude of the magnetic force is related to the density of the magnetic lines of force. The denser the area of magnetic lines of force, the stronger the magnetic field and the greater the magnetic force of the electromagnet. For example, when the current passing through the electromagnet coil is increased or the number of turns of the coil is increased, the magnetic lines of force will become denser, and the magnetic force of the electromagnet will also increase; conversely, when the magnetic lines of force become sparse, the magnetic force will weaken.
6. Relationship between the magnetic force of an electromagnet and the magnetic flux density.                                                                                                                                      The relationship between the magnetic force F of an electromagnet and the magnetic flux density B is F=(B²S₀)/(2μ₀), where S₀ is the air gap area and μ₀ is the vacuum magnetic permeability. It can be seen that when the air gap area and the vacuum magnetic permeability remain unchanged, the magnetic force of an electromagnet is proportional to the square of the magnetic flux density, and the magnetic flux density is proportional to the density of the magnetic force lines. Therefore, the denser the magnetic force lines, the greater the magnetic flux density, and the stronger the magnetic force of the electromagnet.

    Part 4 :  Summary:

     The magnetic line of force are virtual lines used to vividly depict the distribution of the magnetic field around the electromagnet. The magnetic lines of force are closed curves, from       the N pole to the S pole on the outside and from the S pole to the N pole on the inside.

     The density of the magnetic force lines indicates the strength of the magnetic field, and the denser the magnetic field, the stronger the magnetic field. The density of magnetic lines       of force can be quantified by magnetic flux density, which is closely related to the magnitude of the magnetism of the electromagnet. When the air gap area and vacuum magnetic         permeability remain unchanged, the magnitude of the magnetic force is proportional to the square of the magnetic flux density, that is, the denser the magnetic lines of force, the          stronger the magnetic force.

     Electricity and magnetism in electromagnets are two indispensable substances that are interconnected. Electromagnetic induction is widely used in welding, electronic information         technology, mechatronics, etc., and has played an extremely important role in promoting the development of social production and scientific and technological progress.