Question

The earth's magnetic field at the equator is approximately 0.4$G$. Estimate the Earth's dipole moment.

• A. $1.05\times {10}^{23}{Am}^2$
• B. $1.05\times {10}^{-23}{Am}^2$
• C. $5.01\times {10}^{23}{Am}^2$
• D. $5.01\times {10}^{-23}{Am}^2$

Answer 1

The correct option is A $1.05\times {10}^{23}{Am}^2$

$\begin{array}{c}B=\frac{{\mu }_{o}M}{4\pi d^3}=\\ \frac{{\mu }_0}{4\pi }={10}^{-7}w6A^{-1}{m}^{-1}M=dipolemoment\\ d=6400km=6.4\times {10}^{6}m\\ M=\frac{B{d}^3}{{10}^{-7}}=\frac{4\times {10}^{-4}\times {\left(6.4\times {10}^6\right)}^3}{{10}^{-7}}\\ =1.05\times {10}^{23}A{m}^2\end{array}$