A paramagnetic sample shows a net magnetisation of `8Am^-1` when placed in an external magnetic field of `0*6T` at a temperature of `4K`. When the same sample is placed in an external magnetic field of `0*2T` at a temperature of `16K`, the magnetisation will be

Options

A. `32/3A//m`
B. `2/3A//m`
C. 6 A/m
D. 2.4 A/m

Answer

B

Explanation

As `I=chi_(m)Handchi_(m)=C/T` (Curie law),
`I=(CH)/TorI_(1)/I_(2)=(CH_(3)//T_(1))/(CH_(2)//T_(2))=(H_(1)/H_(2))(T_(2)/T_(1))`
or
`M_(2)=M_(1)(H_(2)/H_(1))(T_(1)/T_(2))=8(A//m)[(0.2T)/(0.6T)][(4K)/(16K)]`
`=2/3A//m`