A sample of a paramagnetic salt containing `3xx10^(24)` atomic dipoles each of dipole moment `2xx10^(-23) A-m^(2)` is subjected to a uniform magnetic field of 800 mT and cooled to a temperature of 3.5 K. The degree of magnetic saturation achieved is 10%. If the sample is subjected to a magnetic field of 990 mT and cooled to a temperature of 2.1 K, then the total dipole moment of the sample is

Options

A. `11.25A-m^(2)`
B. `23.5A-m^(2)`
C. `15A-m^(2)`
D. `75A-m^(2)`

Answer

A

Explanation

Initially total dipole moment of sample
= `3xx10^(24)xx2xx10^(-23)xx10/100=6JT^(-1)`
From Curie.s law,
`mpropB/T`, we get
`B_(1)/T_(1)=B_(2)/T_(2)orB_(2)=6xx990/880xx3.5/21=11.25A-m^(2)`