Question

The magnetic field at a point on magnetic equator is `3*1xx10^-5T`. If radius of earth is taken as `6400km`, what is magnetic moment of the assumed dipole at the centre of earth?

Answer 1

As is clear from figure, any point on the magnetic equator lies on equatorial line of the assumed magnetic dipole at the centre of earth,

`:. B_(equa)=(mu_0)/(4pi)(M)/(R^3)`
`M=(4pi)/(mu_0)B_(equa)xxR^3`
`=10^7(3*1xx10^-5)(6400xx10^3)^3`
`M=8*1xx10^(22)Am^2`