Magnetic Induction – Magnetism and Matters Class 12

Magnetic Induction Meaning: The process by which a substance, such as iron or steel, becomes magnetized by a magnetic field. The induced magnetism is produced by the force of the field radiating from the poles of a magnet.

Let a uniform magnetising field $B_{0}$ represented by the parallel lines exist in vacuum. When a soft iron bar (ferromagnetic material) is placed inside the field it gets magnetised. The left end becomes Spole and right end becomes N pole. It produces its own magnetic field. At A and B field is increased while at C and D it is reduced. The magnetic induction is defined as the number of magnetic lines of induction (magnetic lines inside the material) crossing per unit area normally through the magnetic substance.

1.  The magnetic induction B is sum of magnetic field B0 and field $\mu_{0} I$ produced due to magnetisation of substance $B = B _{0}+\mu_{0} I =\mu_{0}( H + I )$
2. Unit is tesla (T) or weber $m ^{-2}\left( Wbm ^{-2}\right)$. These are equivalent to $Nm ^{-1} A ^{-1}$ or $JA ^{-1} m ^{-1}$ The Cgs unit is gauss (G). 1 tesla = $10^{4}$ gauss.