JEE PYQ: Magnetism And Matter Question 7
Question 7 - 2020 (04 Sep 2020 Shift 2)
A paramagnetic sample shows a net magnetisation of $6$ A/m when it is placed in an external magnetic field of $0.4$ T at a temperature of $4$ K. When the sample is placed in an external magnetic field of $0.3$ T at a temperature of $24$ K, then the magnetisation will be:
(1) 1 A/m
(2) 4 A/m
(3) 2.25 A/m
(4) 0.75 A/m
Show Answer
Answer: (4) 0.75 A/m
Solution
By Curie’s law: $\chi \propto \frac{1}{T}$, so $\frac{I_1}{B_1} T_1 = \frac{I_2}{B_2} T_2$ $\frac{6}{0.4} \times 4 = \frac{I_2}{0.3} \times 24 \Rightarrow I_2 = 0.75$ A/m
BETA
