Question

The relative permeability of a material is
(A) 0.999
(B) 1.001
Identify the material

Answer 1

To find the answer to this question we have to know the formula and depending on whether the answer is less than or greater than 0 we have to identify the substance. It should be known to us that if the relative permeability is less than 0 then the substance is known as diamagnetic and if greater than 0 then the substance is known as paramagnetic in nature.

Complete step by step answer:
(A) The relative permeability is given as 0.999
To know the substance from the relative permeability we should know that:
$x = {\mu _r} - 1 \\\ \Rightarrow x = 0.999 - 1 = - 0.001 \\\ \\\$

Hence we can see that x < 0, so the substance is diamagnetic in nature.

(B) The relative permeability is given as 1.001
To know the substance from the relative permeability we should know that:
$x = {\mu _r} - 1 \\\ \Rightarrow x = 1.001 - 1 = 0.001 \\\ \\\$

Hence we can see that x > 0, so the substance is paramagnetic in nature.

Hence i) is diamagnetic and ii) is paramagnetic in nature.

Note: We should know that relative permeability is defined as the ratio between the material permeability and that of the permeability of the substance in the free space or as we know vacuum.
In the question we have also come across the term diamagnetic substance. By diamagnetic materials we mean that they will be substances which will be repelled by any magnetic field. The diamagnetic material will always have a constant value of its relative permeability.
On the other hand, we have also come across the term paramagnetic substance. By paramagnetic substance we mean those materials which are very weakly magnetized whenever they are placed in the presence of an external magnetic field. And this magnetic field is in the same direction as that of the applied field. The paramagnetic material will also have a constant value of its relative permeability.