The earth’s field, it is claimed, roughly approximates the field due to a dipole of the magnetic moment 8 × 1022 JT-1 located at its centre. Check the order of magnitude of this number in some way.
The magnetic field at a point on the equatorial line of the ,agnetic dipole (earth as a magnetic dipole) is given by, B=4πμ0×r3M M=8×1022JY−1 r=6.4×106m ∴B=10−7×(6.4×106)38×1022=0.3×10−4T=0.3G It is really of the order of the observed field of earth
