1.

A paramagnetic sample shows a new magnetisation of 8 "Am"^(-1) when placed in and external magnetic field of 0.6 T at a temperature of 4 K. When the same sample is placed in an external magnetic field of 0.2 T at temperature of 16 K, the magnetisation will be

Answer»

`(32)/(3) Am^(-1)`
`(2)/(3) Am^(-1)`
`6 Am^(-1)`
`2.4 Am^(-1)`

Solution :ACCORDING to Curie.s law, INTENSITY of magnetization DIRECTLY proportional to the magnetic field induction and inversely proportional to its ABSOLUTE temperature.
So magnetisation,
`I prop (B)/( T)`
`therefore I_(1) prop (B_1)/( T_1) and I_(2) prop (B_2)/( T_(2))`
`therefore (I_2)/( I_1) = (B_2)/( B_1) xx (T_1)/( T_2) `
`I_1= 8 "Am"^(-1) , "Taking" B_(1) = 0.6 T, T_(1) = 4K`
`B_(2) = 0.2 T , T_(2) = 16` K
`(I_2)/( 8) = ((0.2)/( 0.6)) ((4)/(16))`
`I_(2) = (8)/(12) = (2)/(3) "Am"^(-1)`


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