Magnetic field and its influence on motion

What is a magnetic field?

A magnetic field is created by the movement of electric charges and can be defined as the area around a magnet where the influence of magnetism is felt. It is a force field that interacts with materials such as iron located in its vicinity.
The magnetic field does not require a medium for propagation and can exist even in a vacuum. It has a greater capacity to store energy than an electric field, making it extremely useful in electromechanical devices such as transformers, motors, and generators.

History of research on the magnetic field

Research on the magnetic field began in the 13th century when Petrus Peregrinus de Maricourt used magnetic needles to study the magnetism of a spherical magnet. He discovered that magnetic force lines intersect at two points, known as magnetic poles. In the 17th century, William Gilbert proposed that Earth acts like a huge magnet.
In the 18th century, Charles-Augustin de Coulomb precisely measured Earth's magnetic field, and Simeon Denis Poisson developed a mathematical model of the magnetic field. However, the 19th century brought revolutionary discoveries. In 1819, Hans Christian Orsted discovered that electric current creates a magnetic field, and André-Marie Ampère suggested that magnetism arises from current flow, not magnetic dipoles. In 1831, Michael Faraday discovered electromagnetic induction and proved that a changing magnetic field produces an electric field. Between 1861-1865, James Clerk Maxwell published equations describing the relationship between electricity and magnetism.
Today, the magnetic field is described as a vector field, and its representation depends on the context. It can be represented by the magnetic field vector or magnetic field lines, which illustrate the direction and intensity of the field.
Magnetic field lines are hypothetical lines that surround magnets and indicate the direction of the magnetic field. The density of the magnetic field lines corresponds to the strength of the magnetic field - the greater the density, the stronger the magnetic field. The magnetic field is strongest around the north and south poles of a magnet and weakens as it moves away from the poles. This can be seen in an experiment where a bar magnet is placed on a sheet of white paper, and iron filings are sprinkled around it. The iron filings will arrange themselves in a precise pattern that mirrors the magnetic field of the magnet, with their concentration being highest near the poles and decreasing as they move away from the poles.

What generates a magnetic field?

A magnetic field can be generated not only by a magnet but also by moving charges or electric currents. Atoms that make up matter have a nucleus containing protons and neutrons, and electrons orbit around this nucleus. A magnetic field is created as a result of the rotation and spinning of protons and neutrons or the nucleus of the atom. The direction of the magnetic field is determined by the directions of the orbit and rotation. The magnetic field is mathematically represented by the letter "B", and its strength is measured in teslas (T).

What is magnetic field strength?

Magnetic field strength, also known as magnetic intensity or magnetic force, is denoted by the symbol H and is a vector.
It can be defined as the ratio required to produce a specified magnetic flux density (B) in a given material per unit length of that material. Magnetic field strength is measured in units of amperes per meter.
The formula for magnetic field strength can be presented as:
H = B/μ - M
Where:
B - magnetic flux density
M - magnetization
μ - magnetic permeability
Tesla is a unit of magnetic field strength. One tesla (1 T) is the field strength that produces one newton of force per ampere of current per meter of conductor.

How is a magnetic field created?

A magnetic field can be created when a charge is in motion. There are two ways of arranging a charge such that it is in motion and continues to generate a useful magnetic field. A magnetic field can be generated whenever an electric charge is in motion. The operation of permanent magnets is based on the movement of electrons around nuclei. Only certain materials can be made into magnets, and some are significantly stronger than others.

Earth's Magnetic Field

Sir William Gilbert first mapped the Earth's magnetic field in 1600. Based on his tests, he discovered that Earth possesses magnetic properties and a magnetic field. If a magnet is freely suspended and can rotate in a horizontal position, it will automatically align and stop in a north-south direction.
The magnet will be oriented in such a way that its north pole will be attracted to the geographic south, and the south pole to the geographic north.

Hypothesis about the source of Earth's magnetic field

There is also a hypothesis that Earth's magnetic field is generated by a magnetic dynamo. According to this theory, the movement of fluids in Earth's core, combined with the Coriolis effect and temperature differences, generates electric currents, which in turn produce a magnetic field.
There is no definitive answer as to which of these hypotheses is most correct, but many scientific studies lean towards the magnetic dynamo theory. In any case, Earth's magnetic field is extremely important for our life on Earth, as it protects us from the harmful effects of solar wind and cosmic radiation.

Properties of magnetic field lines:

Magnetic field lines never intersect.
Field lines follow the path of least resistance between opposite magnetic poles. The magnetic field lines of a bar magnet move in closed loops from one pole to the other.
Magnetic field lines are of equal length.
The density of field lines decreases as they move from an area of higher permeability to an area of lower permeability.
Lines move from the south pole to the north pole in a material magnetic field, while in the air they flow from the north pole to the south pole.
The density of the magnetic field changes with distance from the pole. Its density decreases as it moves away from the pole.
Since the magnetic field has both magnitude and direction, it is a vector quantity.

What is the application of magnetic field in rehabilitation?

Magnetic field has found application in rehabilitation as a method supporting the treatment process of various conditions. However, there are both advantages and disadvantages associated with this solution.

Advantages of magnetic field in rehabilitation include its ability to reduce pain and inflammation, which can accelerate the healing process and reduce patient discomfort. The magnetic field can also stimulate blood circulation and collagen production, which positively affects tissue regeneration. Additionally, magnetic field therapy is non-invasive, meaning it does not require the use of medications or surgical procedures.

However, there are also disadvantages to this method, such as contraindications. Some patients may not respond to magnetic field therapy, making its effectiveness variable. Furthermore, this therapy can be costly and time-consuming, and it requires specialized equipment, which can be a challenge in some medical facilities. There is also a need for further research on the long-term effects of magnetic field therapy to accurately assess its effectiveness and safety.

Despite these pros and cons, magnetic field therapy remains an interesting option in rehabilitation, especially for patients who cannot or do not want to use other treatment methods.