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 Earth axis passes through Greenwich
• D. declination averaged over Earth must be always negative

Answer 1

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

The dipole axis(SN) can be on either side of $N_g$-$N_s$ line. Accordingly, declination varies from $(0^{\circ }+{11.3}^{\circ }W)$ to $(0^{\circ }+{11.3}^{\circ }E)$