Physics

Problem

Three materials P, Q and R have magnetic susceptibilities

\chi_m

equal to

-4.0\times10^{-6}

1.5\times10^{-3}

and

600

respectively. If the same magnetising field

H

is applied to each, which of the following correctly ranks the magnitudes of their magnetisations

M

? a)

|M_R| > |M_Q| > |M_P|

|M_Q| > |M_R| > |M_P|

|M_R| > |M_P| > |M_Q|

|M_Q| > |M_P| > |M_R|

Intuitive explanation

Magnetisation depends on both the material's response to a field (captured by $\chi_m$ ) and the field strength itself. Since all three materials experience the same applied field $H$ , the magnetisation $M = \chi_m H$ is directly proportional to susceptibility—the material with the largest $|\chi_m|$ will have the largest $|M|$ . Simply rank the three susceptibility values by magnitude to find your answer.

Intuitive explanation

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