The source of the magnetic field is created by magnetic energy.There are three sources for creating a magnetic field:

• Permanent magnet: the magnet atom has electrons that rotate around the nucleus creating a magnetic field.

• Current-carrying conductor: in this case there is a wire in which the current circulates, thus creating a magnetic field.

• Electromagnet:this source creates the magnetic field when the current flows through the wire.

Type of magnetic field

There are two types of magnetic fields:

• A static magnetic field = generates fixed electric charges in space. The static magnetic field uses direct current.

• A time-varying magnetic field = uses alternating current and is linked to time variations in the flow of a magnetic field.

The source of the magnetic field is obtained using the laws of the Biot-Savart law in the case that it is created by a current element. The Biot-Savart law establishes the connection between magnetic fields and the currents that create them. On the other hand, in the case of the presence of a solenoid, Ampere's law is used. Ampere's law allows us to know the magnetic fields thanks to the electric currents.

Electric fields vs. magnetic fields

When the electric charge is in motion, it creates two types of fields: the electric field and the magnetic field. Although these two fields have common characteristics such as the intensity decreases as you move away from the electric source; we could find several differences such as:

1. The electric field has a source which is the electric voltage, while the magnetic field is the electric current.


2. The intensity of an electric field is measured in volts per meter, while magnetic fields are measured in amperes.


3. In the case of electric fields, the electric source can be switched off and the electric field will continue to work, unlike magnetic fields, which would not be able to work without the magnetic source switched on.

From the point of view of the electromagnetic field, we can find:

1. Natural sources of electromagnetic fields: the electric ones that are created are due to Argar provision in areas that come from the atmosphere due to natural effects such as a storm.


2. Man-made sources of electromagnetic fields: these man-made sources are intended for applications such as X-rays.

Magnetostatics

Magnetostatics arises from the union of magneto + static. We first see it at the end of the 19th century by Arthur Gordon.

Magnetostatics is the branch of physics that studies magnetic fields that remain fixed over time. Magnetostatics encompasses everything from magnets to electromagnets.

There are different types of magnetostatics:

• Current or voltage-driven coil

• The current path and coil segments

• Permanent magnet

• Magnetic source field

• Stationary current field

Magnetostatic energy is the energy that is stored in the static field. However, magnetization does not mean that it is static, but that it is not easily altered.

Magnetostatic energy is created through the formation of domains. The energy per this unit volume E_m is:

-µ₀= the permeability in vacuum (4π10^-7 H/m)

The vector of m = unit momentum of the volume of the domain under the H field.

The vector of H = magnetic field of the domain.

This magnetostatic energy has the capacity to reduce to zero because of the structure coming from the domains which do not allow external magnetic flux.

Unlike electrostatics, magnetostatics is concerned with the study of magnetic fields in which the current is constant.

One of the most important applications of magnetostatics is the electric motor. This can be used in various household appliances. We can also find them in transformers, bells...

How are magnetic fields measured?

The measurement of magnetostatic fields is measured:

• Gouy's balance: this is an instrument that allows us to measure the magnetic susceptibility of a specific sample. This balance measures the weight at the moment when it is attracted by the magnetic field zone of the poles and the other at the moment when it is repelled, in order to compare them.

• Magnetometers: an instrument that helps us to measure both the direction and the strength of a magnetic field.

The magnetostatic equations allow us to know its behavior. That is why we can find the following magnetostatic laws:

The magnetization of square neodymium magnets is diametrically magnetized.

The most common application of magnetostatics, and the one we see most often, is in micro magnetism, in the form of a magnetic recording device.