Question

Distinguish the magnetic properties of diamagnetic, paramagnetic and ferromagnetic substances in terms of (i) susceptibility (ii) magnetic permeability (iii) coercivity. give an example for each. draw the field lines due to an external magnetic field near (i) diamagnetic(ii) paramagnetic substance.

Answer 1

Based on their behaviour in a magnetising field, materials are classified as diamagnetic, paramagnetic, and ferromagnetic substances.

(i) Susceptibility - Diamagnetic substances have a susceptibility of a low negative value and it is independent of temperature. Paramagnetic substances have a Susceptibility of a low positive value and it is inversely proportional to the absolute temperature. Ferromagnetic substances have a large susceptibility value and it is inversely proportional to the absolute temperature.

(ii) Permeability - Diamagnetic substances have a permeability of slightly less than one. Paramagnetic substances have a permeability of greater than one. Ferromagnetic substances have a very large permeability value. 

(iii) Coercivity - Ferromagnetic substances have a positive coercivity value. Diamagnetic and paramagnetic substances have zero coercivity value.

The attached picture shows the lines near a paramagnetic and a diamagnetic substance when placed in an external magnetic field.