Question

The relative permeability of a substance X is slightly less than unity and that of substance Y is slightly more than unity, then :

• A. X is paramagnetic and Y is ferromagnetic
• B. X is diamagnetic and Y is ferromagnetic
• C. X and Y both are paramagnetic
• D. X is diamagnetic and Y is paramagnetic

Answer 1

Answer: (D)

X is diamagnetic and Y is paramagnetic

Permeability is the measure of the ability of a material to support the formation of a magnetic field within itself. In other words, it is the degree of magnetization.
Relative permeability($\mu$) is the ratio of the permeability of a specific medium to the permeability of free space(${\mu }_0$)
Diamagnetism is the property of an object which causes it to create a magnetic field in opposition of an externally applied magnetic field, thus causing a repulsive effect. Specifically, an external magnetic field alters the orbital velocity of electrons around their nuclei, thus changing the magnetic dipole moment in the direction opposing the external field. Diamagnets are materials with a magnetic permeability less than ${\mu }_0($a relative permeability $<1)$
Paramagnetism is a form of magnetism which occurs only in the presence of an externally applied magnetic field. Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than one.