Question

The earth’s magnetic field at the equator is approximately 0.4 G. What is the earth’s dipole moment?

(a) 0.8 X 10^23 Am^2

(b) 1.0 X 10^23 Am^2

(c) 1.2 X 10^23 Am^2

(d) 1.5 X 10^23 Am^2

This question was addressed to me in homework.

The origin of the question is Parameters topic in section Magnetic Properties of Materials of Engineering Physics II

Answer 1

Correct answer is (b) 1.0 X 10^23 Am^2

Best explanation: We know, BE = \(\frac{\mu_0 m}{4\pi r^3}\)

Given that, BE = 0.4 G = 4 X 10^-5 T. For r, we take the radius of the earth 6.4 X 10^6 m.

Hence, m = 4 X 10^-5 X (6.4 X 10^6)^3 X 4π/μo

= 1.0 X 10^23 Am^2.