Case: Read the passage and answer the question.
The magnetic susceptibility of a substance is a measure of how readily it responds to an external magnetic field. It gives the measure of a substance’s aptness to acquire magnetism. It has no units. Mathematically, it is defined as the ratio of the magnetisation \( M \) to the magnetic intensity \( H \). The susceptibility of a substance is \( 2.7\times10^{-5} \).
What is the magnetisation \( M \) of the substance when the magnetic intensity \( H \) is \( 2\times10^{3}\,\mathrm{A\,m^{-1}} \)?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 5.4\times10^{-2}\,\mathrm{A\,m^{-1}} \)
The passage defines the magnetic susceptibility as the ratio of the magnetisation \( M \) to the magnetic intensity \( H \). So \( \chi=M/H \) and \( M=\chi H \). Since \( \chi \) has no units, \( M \) has the same unit as \( H \).
\( \begin{aligned} M &= \chi H \\ &= 2.7\times10^{-5}\times2\times10^{3}\,\mathrm{A\,m^{-1}} \\ &= 5.4\times10^{-2}\,\mathrm{A\,m^{-1}} \end{aligned} \)