The magnetic susceptibility of a paramagnetic substance at $$-173^o$$C is $$1.5\times 10^{-2}$$ then its value at $$-73^o$$C will be.
  • A
    $$7.5\times 10^{-1}$$
  • B
    $$7.5\times 10^{-2}$$
  • C
    $$7.5\times 10^{-3}$$
  • D
    $$7.5\times 10^{-4}$$

Solution

In paramagnetic substance the magnetic susceptibility
$$\chi =\dfrac{C}{T}\Rightarrow\dfrac{\chi_1}{\chi_2}=\dfrac{T_2}{T_1}$$; Then $$\chi_2=\chi_1\dfrac{T_1}{T_2}$$
Here, $$\chi_1=1.5\times 10^{-2}$$
$$T_1=273-173=100$$K, $$T_2=273-73=200$$K
$$\therefore \chi_2=1.5\times 10^{-2}\times \dfrac{100}{200}=7.5\times 10^{-3}$$