A paramagnetic sample shows a net magnetisation of 6   A / m when it is placed in an external magnetic…

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

Solution

According to Curie's Law,
χ∝1T
Therefore, χ1T1=χ2T2
Also, χ=MB
So, 
M1T1B1=M2T2B2
On substituting the values,
6×40.4=M2×240.3

Therefore, M2=0.75 A m-1

Asked in: JEE Main 2020 (04 Sep Shift 2)

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