# What is magnetic induction? | magnetism & matter class 12

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## Magnetic induction, magnetism & matter class 12

In this short piece of article, we will discuss magnetic induction which is the topic of chapter magnetism and matter of class 12. So let’s get started… [latexpage]

Let us suppose that a toroidal solenoid is wound around an iron ring. And It is placed in any external magnetic field $B_0$. We know that when a magnetic material is placed in an external magnetic field, magnetism is induced in it. It is important for us to know that how this magnetization occurred.

When a magnetic material is placed in an external magnetic field. Under the influence of this magnetizing field, $B_0$ magnetic moment of atomic current loops of the magnetic material tries to align itself along or against the magnetizing field $B_0$. Due to this, a net current develops on the surface of the magnetic material that’s called magnetization surface current $I_M$.

This magnetizing surface current indices magnetic field $B_M$ to the material which is given by $$B_M = \mu nI_{M}$$

## Magnetic induction definition class 12

So we have seen that if a toroidal solenoid is bound around a magnetic material such as a ring and if it is placed in any external magnetizing field $B_0$ then magnetizing surface current induces a magnetic field to the material due to this the total magnetic field inside the magnetic material increases.

Definition – The total magnetic field inside a magnetic material is the sum of magnetising field and the additional magnetic field which is produced due to magnetisation of the material and is magnetic induction $\vec{B}$.

The magnetic induction can also be defined as the total number of magnetic field lines crossing per unit area normal through the magnetic material.

The SI unit of magnetic induction is Tesla (T) or Weber per metre square $(Wb m^{-2})$ which is equivalent to $Nm^{-1}A^{-1}$ or $JA^{-1}m^{-2}$