Question

What is permeability of free space? Why we are multiplying it?is it a constant?

Answer 1

The permeability of free space is just a constant which is needed for conversion between different units in the SI system of units and other similar systems of units. It other systems of units it doesn't even exist. The permeability of free space (a vacuum ) is a physical constant equal to approximately 1.257 x 10 -6 h/m . It is symbolized µ o . Permeability in general is symbolized µ, and is a constant of proportionality that exists between magnetic flux density and magnetic field strength in a given medium. In certain metals, notably iron and nickel and alloys containing them, µ is substantially greater than µ o .

We multiply it to convert between diferent units in the SI system.
Yes , it is constant