The magnetic moment of the assumed dipole at the earth's centre is `8.0 xx 10^22 A m^2`. Calculate the magnetic field `B` at the geomagnetic poles of the earth. Radius of the earth is `6400 km`.

Answer

`60muT`

Explanation

The geomagnetic poles lie on axial line of the assumed dipole at `d=6400km=6*4xx10^6m`
`:. B=(mu_0)/(4pi)(2M)/(d^3)=(10^-7xx2xx8xx10^(22))/((6*4xx10^6)^3)`
`~~60xx10^-6T=60muT`