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A substance whose permeability is less than the permeability of free space is?
Diamagnetic
Paramagnetic
Ferromagnetic
Not a magnetic substance
Diamagnetic
A substance whose magnetic permeability is less than the permeability of free space (╬╝<╬╝0тАЛ) is classified as a diamagnetic material. For such substances, the relative permeability is slightly less than unity (╬╝rтАЛ<1). Consequently, their magnetic susceptibility is small and negative (╧ЗmтАЛ<0).
A substance whose magnetic permeability is less than the permeability of free space (╬╝<╬╝0тАЛ) is classified as a diamagnetic material. For such substances, the relative permeability is slightly less than unity (╬╝rтАЛ<1). Consequently, their magnetic susceptibility is small and negative (╧ЗmтАЛ<0).
╬╝rтАЛ=╬╝0тАЛ╬╝тАЛ тАФ Relative permeability formula
╧ЗmтАЛ=╬╝rтАЛтИТ1 тАФ Magnetic susceptibility formula
B=╬╝0тАЛ(H+M) тАФ Relation between magnetic induction, field strength, and magnetization
When placed in an external magnetic field, the orbital motion of electrons in diamagnetic atoms shifts, inducing a magnetic dipole moment opposing the applied field according to Lenz's law. This causes diamagnetic substances to be weakly repelled by strong magnetic fields.
For diamagnetic materials, ╬╝rтАЛ<1 and ╧ЗmтАЛ<0 (small and negative).
Diamagnetism is independent of temperature.
Diamagnetic materials tend to move from stronger to weaker parts of a non-uniform magnetic field.
Exhibits perfect diamagnetism in superconductors (Meissner Effect).
Does not retain residual magnetism when external field is removed.
Cannot be magnetized permanently for industrial magnetic storage.
Interaction with magnetic fields is extremely weak for non-superconducting materials.
Magnetic levitation using superconductors.
Bismuth-based magnetic field sensors.
Magnetic shielding components.
Examples of diamagnetic materials include Bismuth, Copper, Water, Gold, Mercury, and Silver.
Option B (Paramagnetic) is incorrect because paramagnetic materials have ╬╝rтАЛ>1 and ╧ЗmтАЛ>0.
Option C (Ferromagnetic) is incorrect because ferromagnetic materials have ╬╝rтАЛтЙл1 and large positive susceptibility.
A is correct тАФ Diamagnetic substances have a permeability less than free space permeability, giving a relative permeability less than 1.
Always remember for competitive exams: Diamagnetic (╬╝rтАЛ<1, ╧ЗmтАЛ<0), Paramagnetic (╬╝rтАЛ>1, ╧ЗmтАЛ>0), and Ferromagnetic (╬╝rтАЛтЙл1, ╧ЗmтАЛтЙл0).