The magnetic field of Earth can be modelled by that of a point dipole placed at the centre of the Earth. The dipole axis makes an angle of 11.3° with the axis of Earth. At Mumbai, declination is nearly zero. Then, (a) the declination varies between 11.3° W to 11.3° E. (b) the least declination is 0°.(c) the plane defined by dipole axis and Earth axis passes through Greenwich. (d) declination averaged over Earth must be always negative.

The magnetic field of Earth can be modelled by that of a point dipole

1.	The magnetic field of Earth can be modelled by that of a point dipole placed at the centre of the Earth. The dipole axis makes an angle of 11.3° with the axis of Earth. At Mumbai, declination is nearly zero. Then, (a) the declination varies between 11.3° W to 11.3° E. (b) the least declination is 0°.(c) the plane defined by dipole axis and Earth axis passes through Greenwich. (d) declination averaged over Earth must be always negative.
Answer» (a) the declination varies between 11.3° W to 11.3° E.