The susceptibility of magnesium at 27°C is \( 1.2 \times 10^{-5} \). Its susceptibility at 200 K will be
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 1.8 \times 10^{-5} \)
Magnesium is paramagnetic, and the susceptibility of a paramagnetic substance follows Curie's law: it is inversely proportional to the absolute temperature.
\( \displaystyle \chi = \frac{C}{T} \;\Rightarrow\; \chi_1 T_1 = \chi_2 T_2 \)
\( T_1 = 27^\circ\mathrm{C} = 300\,\mathrm{K} \)
\( T_2 = 200\,\mathrm{K} \)
\( \displaystyle \chi_2 = \chi_1\,\frac{T_1}{T_2} = 1.2\times10^{-5} \times \frac{300}{200} = 1.8\times10^{-5} \)
Cooling the sample makes the thermal agitation weaker, so the atomic dipoles line up more easily and the susceptibility rises.