(a) The tree independent quantities conventionally used for specifying earth's magnetic field are:

(i) Magnetic declination,

(ii) Angle of dip, and 

(iii) Horizontal component of earth's magnetic field

(b) The angle of dip at a point depends on how far the point is located with respect to the North Pole or the South pole. The angle of dip would be greater in Britain (it is about 70^o) than in southern India because the locaton of Britain on the globe is closer to the magnetic north pole.

magnetic field lines emanate from a magnetic north pole and terminate at a magnetic south pole. hence, in a map depicting earth's magnetic field lines, the field lines at Melbourne, Australia would seem to come out of the ground.

(d) If a compass is located on the geomagnetic North pole or South pole, then the compass will be free to move in the horizontal plane while earth's field is exactly vertical to the magnetic poles. In such a case, the compass can point in any direction.
(e) Magnetic moment,$\mathrm{M}=8\times {10}^{22}{\mathrm{JT}}^{-1}$

Radius of earth,$\mathrm{r}=6.4\times {10}^6 \mathrm{m}$

Magnetic field strength, B= $\frac{{\mathrm{\mu }}_0}{4\mathrm{\pi }}\frac{\mathrm{M}}{{\mathrm{r}}^3}$

Where, ${\mathrm{\mu }}_0$=Permeability of free space=$4\mathrm{n}\times {10}^{-7}\mathrm{T} \mathrm{m} {\mathrm{A}}^{-1}$

$\therefore \mathrm{B}=\frac{4\mathrm{\pi }\times {10}^{-7}\times 8\times {10}^{22}}{4\mathrm{\pi }\times \left(6.4\times {10}^6\right)}=0.3 \mathrm{G}$