Question

Relative permeability of diamagnetic material is slightly:
1. More than two
2. More than unity
3. Less than unity
4. More than five

Answer 1

Correct Answer - Option 3 : Less than unity

Magnetic permeability:

• Relative increase or decrease in the resultant magnetic field inside a material compared with the magnetizing field in which the given material is located.
• It is the property of a material that is equal to the magnetic flux density B established within the material by a magnetizing field divided by the magnetic field strength H of the magnetizing field. 
• Magnetic permeability is thus defined as μ = B/H.

• A diamagnetic material has a constant relative permeability of slightly less than 1.
• When a diamagnetic material such as bismuth is placed in a magnetic field, the external field is partly expelled then the magnetic flux density within it is slightly reduced.
• A paramagnetic material has a constant relative permeability of slightly more than 1.
• When a paramagnetic material such as platinum is placed in a magnetic field, it becomes slightly magnetized in the direction of the external field.
• A ferromagnetic material such as iron does not have a constant relative permeability.
• The permeability of ferromagnetic materials varies greatly with field strength. As the magnetizing field increases, the relative permeability increases reaches a maximum and then decreases.
• In free space, the magnetic flux density is the same as the magnetizing field because there is no matter to modify the field. The permeability B/H of space is dimensionless and has a value of 1.