Question

Which of the following substances has magnetic permeability less than that of free space?

• A. Sodium
• B. Iron
• C. Aluminium
• D. Copper

Hint:

Diamagnetic materials, such as copper, have a magnetic permeability slightly less than that of free space. In contrast, ferromagnetic materials like iron have much higher permeability.

Answer 1

The Correct Option is D

Magnetic permeability is a property that indicates the ability of a material to conduct magnetic field lines. The magnetic permeability of a material is typically compared to the permeability of free space, denoted by \( \mu_0 \). - Iron: It is a ferromagnetic material, meaning its magnetic permeability is much greater than that of free space. - Aluminium: It is a paramagnetic material, meaning its permeability is slightly greater than that of free space, but not as high as ferromagnetic materials. - Sodium: It is a paramagnetic material, and its magnetic permeability is slightly greater than that of free space, similar to aluminium. - Copper: It is a non-magnetic material, and its magnetic permeability is slightly less than that of free space, because it has a weak diamagnetic property. Hence, the correct answer is: \[ \boxed{D} \text{ Copper} \]