Flux density: The intensity of a magnetic field

The flux density, also known as magnetic flux density, is a physical quantity that describes the strength of a magnetic field at a specific point. It is represented by the symbol B and measured in the unit Tesla (T). The flux density indicates how much magnetic flux passes through a defined area.

Definition of flux density

Mathematically, the magnetic flux density is defined as the ratio of the magnetic flux ( Phi ) to the area through which the flux flows ( A ):

B = Φ / A

Where:

• B: Magnetic flux density in Tesla (T)
• Φ: Magnetic flux in Weber (Wb)
• A: Area in square metres (m²)

The flux density is a vector quantity and therefore has both a direction and a magnitude.

Properties of flux density

• Direction: The direction of the flux density corresponds to the direction of the field lines of a magnetic field.
• Influence of materials: The flux density is influenced by the permeability of the material in which the magnetic field occurs.
• Strength: The flux density is proportional to the strength of the magnetic field lines. A high density of field lines corresponds to a high flux density.

Measuring the flux density

The flux density is measured using devices such as Gaussmeters or Hall sensors. These measuring devices are used in laboratories, industry and for geophysical investigations.

Typical values for flux density

• Earth's magnetic field: Around 30-60 microtesla (μT), depending on the geographical location.
• Household magnets: Between 0.1 and 0.5 Tesla (T).
• Neodymium magnets: Up to 1.4 Tesla (T).
• Magnetic resonance imaging (MRI): 1.5 to 3 Tesla (T), in special cases up to 7 Tesla (T).

Applications of flux density

Magnetic flux density is a key parameter in many technical and scientific applications:

• Electric motors: The flux density determines the efficiency and performance of a motor.
• Transformers: In transformers, flux density is used to optimise the magnetisation of the core.
• Sensor technology: Flux density sensors measure magnetic fields precisely, e.g. in vehicles or industrial systems.
• Geophysics: The flux density of the Earth's magnetic field is analysed to detect tectonic activity or local anomalies.

Interesting facts about flux density

Did you know that the highest flux density ever generated in a laboratory was over 100 Tesla? These extreme magnetic fields are used in research to investigate new materials and analyse the behaviour of electrons under extreme conditions.