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

Answer

B

Explanation

As `I=chi_(m)H` and `chi_(m)=(C )/(T)` (Curie law),
`I=(CH)/(T)` or `(I_(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)/(3)A//m`