What is Weber?

In the 19th century, Weber unit of magnetic flux was named as an honour to a German Physicist named Wilhelm Eduard Weber (1804-1891).

Weber is the unit of magnetic flux that causes the electromotive force of one volt in a circuit of one rotation when generated/removed in one second.

In terms of Faraday’s law, the SI unit of flux is Weber, it is related to a changing magnetic flux through a loop to the electric field around the loop. A change in flux of one weber per second induces an electromotive force of one volt or it produces an electric potential difference of one volt across two open-circuited terminals.

What is Magnetic Flux?

In this article, we will understand the flux definition with various flux units in detail.

Do you know what is flux and what is the SI unit of magnetic flux? Well! Flux is the number of magnetic field lines passing through a cross-sectional area perpendicularly.

Flux Definition: 

A magnetic flux is the product of the average magnetic field and the perpendicular area that it penetrates. 

In mathematical terms, we can reinstate the above statement as;

                     ɸ = B.A



ɸ = magnetic flux, where the unit of magnetic flux is Weber (Wb) or Tesla metre squared or (Tm2).

Here, Tesla is equal to Weber per metre square. It is also the unit of flux density. 

B = Magnetic field strength. It is measured in SI base units of Ampere per metre or A/m. It also 

A = perpendicular area through which magnetic field lines cross.

So, the magnetic flux depends on both the magnetic strength and area.

We can see the dot product of B and A. Here, we can rewrite the above equation as;

ɸ = B.A Cosθ


Cosθ = It is the angle between the planar area and the magnetic flux. 

Magnetic Flux

Faraday’s awesome insights lay the foundation for finding a simple mathematical relation to elaborate the explanation of the series of experiments that he conducted on electromagnetic induction (EMI).

Faraday made several contributions to science (especially in magnetism) and till present, he is widely known as the greatest experimental scientist of the nineteenth century. 

Before we start appreciating his great works, let us understand the concept of magnetic flux, which plays a major role in EMI.

For calculating the magnetic flux, we consider the field-line image of a magnet/the system of magnets, as shown in the image below:

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In this image, we can see that the magnetic flux crosses a planar area indicated by the letter ‘ A’ that is placed in a uniform magnetic field of magnitude given by B (which is actually the magnetic field strength). 

The product of these two quantities, viz B and A is given as the scalar product of these. The angle (Cosθ) at which the field lines pass through the given surface area plays a significant role here. If the field lines intersect the area at a certain angle, that is,

  • When the angle between the magnetic field vector B and the area vector A is nearly equal to or equal to 90°, then the resulting flux is very low or zero; respectively. 

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  • When the angle is equal to 0°, the resulting flux is maximum.

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Point to Ponder:

Magnetic flux is a quantity of convenience in Faraday's Law statement and in the explanation of objects like transformers and solenoids.

Dimension of Weber

The practical meter-kilogram-second (MKS), the SI unit of magnetic flux is equal to that flux in which an armature of one turn produces in it an electromotive force of one volt as soon as the flux is reduced to zero at a uniform rate in one second.

Since we know that the SI unit of magnetic flux is Weber; therefore, we can express Weber in terms of derived units as Joules per ampere or J/A.


One Weber = One V·s = 1 (Tm2) = 1 J/A.

So, the unit of weber is kgm2s-2A-1, and

The dimension of Weber is [ML2T-2A-1].

Point To Note:

  • In the CGS system of units, a.k.a Centi-Gram-Second, one weber is equal to 108 Maxwells.

  • The two flux units are Weber and Maxwell.

Weber Number

Weber's number was named after a professor of naval mechanics at the Polytechnic Institute of Berlin named Moritz Weber (1871–1951).

The Weber number (We) is a dimensionless number employed in the field of fluid mechanics. Weber number is often useful in analysing fluid flows whenever there is an interface between two different fluids, especially for fluids with multiphase flowing with strongly curved surfaces.

FAQs (Frequently Asked Questions)

1. What is Magnetism?

Ans: Magnetism is one of the sequences of physical phenomena that are intervened by magnetic fields. 

Electric currents and the magnetic moments of minute particles inside the object give rise to a magnetic field, which affects other currents and magnetic moments. 

Magnetism is one aspect of the combined principle of electromagnetism. 

The most familiar effects of magnetism occur in ferromagnetic materials that get strongly attracted by magnetic fields and can retain their permanent magnetic behaviour by producing magnetic fields themselves. 

2. What are the Applications of the Magnetic Field?

Ans: Some applications of the magnetic field are  Electromagnets, AC and DC motors, electric generators, transformers, electromagnetic wave propagation, maglev or Magnetic Levitation, and also in the Magnetic Resonance Imaging system.

3. What are the Applications of Magnetic Flux?

Ans: The applications of magnetic flux include the magnetic sensor. A magnetic sensor is used for measuring the direction and the strength of a magnetic field. These applications of magnetic flux are mainly valid in the magnetic sensor for android, navigation, industrial, and scientific measurement applications.

4. What is Flux Density?

Ans: We define the flux density as the measure of the number of magnetic lines of force passing through a cross-sectional area.

The total amount of the flux produced by a magnet is important, to understand how dense or concentrated the flux is per unit of planar area. So, the flux per unit of cross-sectional area is called flux density.

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