Question

The earth’s field, it is claimed, roughly approximates the field due to a dipole of magnetic moment 8 x 10²² JT^-1 located at its centre. Check the order of magnitude of this number in some way.

Answer 1

The magnetic field at a point on the equatorial line of the magnetic dipole (earth as a magnetic dipole) is given by,

It is really of the order of the observed field of earth.