Question

The magnetic field of earth at the equator is approximately $4\times {10}^{-5}T$. The radius of earth is $6.4\times {10}^{6}m$. Then the dipole moment of the earth will be nearly of the order of :

• A. ${10}^{23}A{m}^2$
• B. ${10}^{20}A{m}^2$
• C. ${10}^{16}A{m}^2$
• D. ${10}^{10}A{m}^2$

Answer 1

The correct option is A ${10}^{23}A{m}^2$

Answer is A
We know that, magnetic field of earth is
$B=\frac{{\mu }_{o}m}{4\pi r^2}$
Dipole moment, $d=2mr$
$d=\frac{B\times 4\pi r^2}{{\mu }_o}\times 2\times r=2100\times {10}^{20}$
$d={10}^{23}A{m}^2$