The value of relative magnetic permeability ( \[{\mu _r}\] ) for ferromagnetic materials is
A. ( \[{\mu _r} = 1)\]
B \[.({\mu _r} > > 1)\]
C \[.({\mu _r} < 1)\]
D. ( \[{\mu _r} > 1)\]

Hint:Magnetic permeability in electromagnetism is a property of a magnetic material which supports the formation of a magnetic field. The permeability is the ability of the material to allow the magnetic flux in an object.

Complete answer:
The relative permeability of magnetic material is the ratio of its absolute permeability to that of air. In electromagnetism, permeability is the measure of the ability of a material in which it forms the magnetic field within itself. Hence, it responds to the degree of magnetization to an applied magnetic field.

Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins to line up parallel with each other in a region called a domain.Within the domain, the magnetic field is intense, but in a bulk sample the material will usually be unmagnified because the many domains will themselves be randomly oriented with respect to one another.

Ferromagnetic material supports itself in the fact that a small imposed magnetic field to that material, for example from a solenoid, can cause the magnetic domains to line up with each other and the material is said to be magnetized. The driving magnetic field will then be increased by a large factor which is usually expressed as a relative permeability for the material.Thus, relative permeability for ferromagnetic material is very high i.e, \[({\mu _r} > > 1)\] .

Hence the correct option is B.

Note:The relative permeability is also very large and varies linearly with the magnetizing field the field inside the material is much stronger than the magnetizing field. They have a tendency of pulling in a large number of lines of force by the material.Ferromagnetic materials do not have a constant relative permeability and vary from 1000 to 100000.