Four materials A, B, C and D have the magnetic susceptibilities \( \chi_{mA}, \chi_{mB}, \chi_{mC} \) and \( \chi_{mD} \) respectively. Which are related as \( \chi_{mD} \lt \chi_{mC} \lt \chi_{mB} \lt \chi_{mA} \). Which material can be magnetised with maximum ease?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A
The magnetic susceptibility is the magnetisation produced per unit magnetic intensity.
\( \displaystyle \chi_m = \frac{M}{H} \)
For the same applied \( H \), the material with the largest susceptibility acquires the largest magnetisation, so it is the easiest to magnetise.
In the given relation \( \chi_{mA} \) is the largest, so material A is magnetised with maximum ease.
NCERT (2026-27):
Magnetisation and Magnetic Intensity – “… The latter quantity can be influenced by external factors. This influence is mathematically expressed as
\( \displaystyle \chi = \frac{M}{H} \qquad (5.13) \)
where \( \chi \), a dimensionless quantity, is appropriately called the magnetic susceptibility. It is a measure of how a magnetic material responds to an external field.”