2 March 2024

magnetic flux density It is a concept of physics that refers to the number of magnetic field lines that pass through a given surface. It is a measure of the amount of magnetic field passing through a surface. In this article we will describe this concept in detail, as well as the characteristics and formulas that you need to know to understand the magnetic flux density.

What is the magnetic flux density used for?

Magnetic flux density is useful to describe the effects of magnetic force on some object that occupies a certain area. It is a measure that is tied to the particular area of ​​choice.

Magnetic flux density is used in a large number of applications. Among them we can mention the manufacture of magnets, the generation of electricity and medicine. However, this measurement is also important in the electronic industry, since it allows to design electronic components that can be operated and controlled electrically.

Magnetic flux characteristics

Next we describe the characteristics that define the magnetic flux.

  • The magnetic flux, regularly called Φ, is a measurable physical quantity characterizing the intensity and spatial distribution of the magnetic field.
  • This quantity is equal to the flux of the magnetic field through an oriented surface.
  • Its unit of expression in the International System of Units is the weber (Wb), a homogeneous unit with the volt-second.
  • Through an oriented infinitesimal surface element, the magnetic density is the Scalar product of these two vectors.
  • The flux through the surface S is then the integral.
  • It is related to the magnetic inductionwhich is the magnetization that occurs in a material due to the presence of a magnetic field.

How to calculate the magnetic flux density?

It is possible to choose the size of an area determined and its orientation relative to the magnetic field. If the field line representation of the magnetic field is used, then each field line passing through a given area contributes some magnetic flux.

The angle at which the field line intersects the box is also important. A grazing field line contributes a small field component to the magnetic flux.

To calculate the magnetic fluxonly the component of the magnetic field vector that is normal to the test area is included.

Therefore, the magnetic flux density It is calculated by dividing the magnetic flux (in webers) times the surface area (in square meters) that the magnetic field traverses. Another relevant fact is that the magnetic flux density is measured in teslas (T), in the International System.

Are magnetic flux and magnetic flux density the same?

No, they are not the same. magnetic flux It is measured in webers (Wb) while the magnetic flux density It is measured in teslas (T).

Magnetic flux density is a measure of the amount of magnetic field passing through a given surface. On the other hand, magnetic flux is a measure of the total number of magnetic field lines passing through a surface.

What is a weber?

a weber is the unit of measurement used for magnetic flux. It is the amount of magnetic flux that crosses a surface of one square meter, when the magnetic field has an intensity of one tesla perpendicular to the surface. One weber is also equivalent to 10^8 magnetic field lines per square meter.

What is the symbol for magnetic flux density?

The symbol for the magnetic flux density is the letter ‘B’. The magnetic flux density is represented in teslas (T) and is calculated by dividing the magnetic flux by the area.

magnetic flux formula

The formula for magnetic flux is: F = B x A. “F” represents the magnetic flux measured in webers (Wb). “B” represents the magnetic flux density in teslas (T). While “A” represents the area of ​​the surface that the magnetic field crosses, measured in square meters.

Examples of magnetic flux density

Here we detail several practical examples of magnetic flux density.

Earth’s magnetic flux

Earth’s magnetic flux originates from its core, where the movement of liquid iron generates a magnetic field. The flux lines trap the radiation and create a magnetosphere that acts as a shield around the Earth. The Earth’s magnetic flux also affects compasses, allowing them to point toward magnetic north. In addition, it is responsible for natural phenomena such as the northern and southern lights.

Magnetic flux of a bar magnet

In a bar magnet, the magnetic flux density flows from the north pole to the south pole, creating a closed loop structure around the magnet. The magnetic flux lines represent the direction and strength of the magnetic field generated by the magnet.

The magnetic flux around the bar magnet will be zero if the magnetic field is parallel to the area. However, if the magnetic field is perpendicular to the area, the magnetic flux will be maximum.

toroid magnetic flux

When current flows through the coils of the toroids, magnetic fields are generated inside the coil, while the magnetic field outside the coil is zero.

This is because the magnetic flux is confined within the powdered iron core of the toroid, which allows for high efficiency in the energy transfer.

Magnetic flux in the transformer

In a transformer, the main coil induces current in the core and opposes the charge to generate the magnetic flux. This acts as a link between both windings, managing to transfer energy from the primary coil to the secondary.

When the AC power supply decreases or increases in the opposite direction, the magnetic density changes. This induces a current in the secondary coil. In this way, the magnetic flux in the transformer allows electrical energy to be transferred from one circuit to another.

Magnetic flux in the wire loop

A magnetic flux is generated when a magnet approaches a loop of wire. This flow is intensified with energy in a downward direction, and magnetic fields oppose the flow.

In a open loopthe change in magnetic flux can induce a current in the wire, proving Faraday’s law of electromagnetic induction.

How do we measure the magnetic field?

The magnetic field can be measured using a magnetometer, a device that measures the strength of the magnetic field at a certain position.

For example, if you move a small probe of a magnetometer (without rotating it) into an area near a large sheet of magnetic material, and the apparatus registers a constant reading, then the magnetic flux passing through the area is B A2.

What is the intensity of the magnetic flux?

The intensity of the magnetic field, or magnetic field H, is a measure of the amount of magnetization that a magnetic field produces in a magnetic material.

This is represented by the symbol H and is measured in amperes per meter (A/m). Both are important properties of magnetic fields, but they represent different aspects of it.

The intensity of the magnetic flux is also known as the force acting on a body per unit charge, while the intensity of the gravitational field is the force acting on a body per unit mass.

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