Magnetics 5 Question 3
3. A paramagnetic material has $10^{28}$ atoms $/ m^{3}$. Its magnetic susceptibility at temperature $350 K$ is $2.8 \times 10^{-4}$. Its susceptibility at $300 K$ is
(2019 Main, 12 Jan II)
(a) $3.726 \times 10^{-4}$
(b) $3.672 \times 10^{-4}$
(c) $2.672 \times 10^{-4}$
(d) $3.267 \times 10^{-4}$
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Answer:
Correct Answer: 3. (d)
Solution:
- From Curie’s law for paramagnetic substance, we have
Magnetic susceptiblity $\chi \propto \frac{1}{T}$
$$ \begin{array}{ll} \therefore & \frac{\chi _2}{\chi _1}=\frac{T _1}{T _2} \Rightarrow \chi _2=\frac{\chi _1 \cdot T _1}{T _2} \\ \Rightarrow \quad & \chi _2=\frac{2.8 \times 10^{-4} \times 350}{300}=3.267 \times 10^{-4} \end{array} $$
