Question

The magnetic field of the earth can be modelled by that of a point dipole placed at the centre of the earth. The dipole axis makes an angle of ${11.3}^o$ with the axis of the earth. At Mumbai, declination is nearly zero. Then,

• A. The declination varies between ${11.3}^o$ W to ${11.3}^o$E
• B. The least declination is $0^o$
• C. The plane defined by dipole axis and the earth axis passes through Greenwich
• D. Declination averaged over the earth must be always negative

Answer 1

The correct option is A The declination varies between ${11.3}^o$ W to ${11.3}^o$E

Since the axis of the magnetic dipole placed at the centre of earth makes an angle of ${11.3}^o$ with the axis of earth, the two possibilities arises as shown in given figure. Hence, the declination varies between ${11.3}^o$W to ${11.3}^o$E.