Every iron atom in a ferromagnetic domain has a magnetic dipole moment equal to `9.27 xx 10^(-24) A m^(2)`. A ferromagetic domain in iron has the shape of a cube of side ` 1mum`. The maximum dipole moment occurs when all the dipoles are alligned. The molar mass of uiron is 55 g and its specific gravity is 7.9 .The magnetisation of the domain is .

Options

A. `7.0 A - m^(2)`
B. `7.8 A - m^(2)`
C. `8.8 A -m^(2)`
D. `9.6 A - m^(2)`

Answer

C

Explanation

Mass of bar ` = 6 xx 1 xx 1xx 7.8 gm`
`= 46.8 gm` .
Dipole moment of bar ( dipole moment of one atom ) `xx` (number of atoms )
` = 1.75 xx 10^(-23) xx (46.8xx 6.02 xx 10^(23))/( 56) = 8.8 A - m^(2) ` .