In order to understand what magnetic induction is, and how it originates, we need to define a physical quantity called the magnetic induction flux. This magnitude is vector is symbolized by **Φ.**

Even if there is magnetic induction flux over any body, regardless of its shape or material, we will define it only for the particular case of a flat surface of surface area A, which may be the area bounded by a loop, immersed in a magnetic field. uniform like this:

Then we can write the magnetic induction flux as the product of the magnetic induction vector (magnetic field) by surface area **THE** and the cosine of the angle θ, formed between and a line perpendicular to the surface, called the normal line. Like this:

The unit adopted to measure the magnetic induction flux by SI is the weber (Wb), named after the German physicist Wilhelm Webber, and features tesla per square meter. .

It is also possible to associate the magnetic induction flux with the number of induction lines that cross the surface, so that:

- If the normal line to the surface is perpendicular to the magnetic induction vector, no induction line will cross it, so the flow will be null. This is proved by the magnetic flux equation since

- If the normal surface line is parallel to the magnetic induction vector, the maximum number of induction lines will cross it, so the flux value will be maximum since is that Where .

If the magnetic induction vector and area are constant values and only the angle θ is free to vary, then we can make a graph of **Φ**x**θ**, where we will see the flow variation as a function of the variation of θ, in a lagged sinusoid of (cosine graph).