If χ stands for the magnetic susceptibility of a given material, identify the class of materials for which: (i) −1≤χ<0 (ii) 0<χ<ε (ε stands for a small positive number). (a) Write the range of relative magnetic permeability of these materials. (b) Draw the pattern of the magnetic field lines when these materials are placed in an external magnetic field.
Solution
(i) For −1≤χ<0 the susceptibility is negative, so the material is diamagnetic. (ii) For 0<χ<ε the susceptibility is small and positive, so the material is paramagnetic. (a) Using μr=1+χ: for the diamagnetic 0≤μr<1, and for the paramagnetic 1<μr<1+ε. (b) For the diamagnetic the external field lines are expelled and thinned inside the specimen; for the paramagnetic the field lines are slightly drawn in and concentrated inside.
