Question

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 1

Answer: (A)

The declination varies between 11.3° W to 11.3°E.

Answer 2

Since the axis of the magnetic dipole placed at the centre of earth makes an angle of $11.3 ^ { \circ }$ with the axis of earth the two possibilities arise as shown in above figure. Hence the declination varies between $11.3 ^ { \circ } \mathrm { W }$ to