Explain the magnetic fields of the Earth. and Give the value of magnified of earth.

To describe the magnetic field of the earth at a point on its surface, we need to specify three quantities.

$(i)$ The declination $D$

$(ii)$ The angle of dip or the inclination $I$

$(iii)$ The horizontal component of Earth's field $\mathrm{H}_{\mathrm{E}}$

$(iv)$ The vertical component of earth's field $Z_{E}$

All these are known as the elements of the earth's magnetic field.

From figure,

$\mathrm{H}_{\mathrm{E}}=\mathrm{B}_{\mathrm{E}} \cos \mathrm{I}...(1)$

$\mathrm{Z}_{\mathrm{E}} =\mathrm{B}_{\mathrm{E}} \sin \mathrm{I}....(2)$

$\therefore \quad \tan \mathrm{I}=\frac{\mathrm{Z}_{\mathrm{E}}}{\mathrm{H}_{\mathrm{E}}}...(3)$

$\text { and } \mathrm{B}_{\mathrm{E}}=\sqrt{\mathrm{H}_{\mathrm{E}}^{2}+\mathrm{Z}_{\mathrm{E}}^{2}}...(4)$

Of the order of $10^{-5} \mathrm{~T}$