Question

Earth’s magnetic field at the equator is approximately 4 × 10^-5 T. Calculate Earth’s dipole moment.

(Radius of Earth = 6.4 × 10⁶ m, µ₀ = 4π × 10^-7 SI units)

Answer 1

Consider earth’s magnetic field as due to a bar magnet at the centre of earth, held along the polar axis of earth.

∴ B_eq = \(\frac{\mu_0}{4\pi}\,\frac{m}{r^3}\) (where, R = radius of earth)

= 4 × (6.4)³ × 1020

= 1048 × 10²⁰

∴ M = 1.048 × 10²³ Am²