The earth's magnetic field at the equator is approximately `0*4G`, Estimate the earth's dipole moment.

Explanation

From Eq. (5.7) the equatorial magnetic field is.
`B_(E)=(mu_(0)m)/(4pir^(3))`
We are given that `B_(E)- 0.4G=4xx10^(-5)T`. For r. we take the radius of the earth `6.4xx10(6)m`. Hence.
`m=(4xx10^(-5)xx10^(6))^(3))/(mu_(0)//4pi)=4xx10(2)xx(0.4xx10^(6))^(3) (mu_(0)//4pi=10^(-7))`
`=1.05xx10^(23)Am^(2)`
This is close to the value `8xx10^(22)Am^(2)` quoted in geomangetic texts.