The earth magnetic field at the equator is approximately 04.G. Estimate the earth's dipole moment.

Explanation

Magnetic field of a bar magnet at far equatorial point is given by,
`B_(e) = (mu_0)/( 4pi ) ((m)/( r^3) )`
`therefore m= (4 pi B_(e) r^(3) )/( mu_0)`
`therefore m= (4 pi B_(e) R_(e)^(3) ) /( mu_(0) ) " "( because "here" r=R_(e) = "equatorial radius of Earth")`
`therefore = ((4 pi )(0.4 xx 10^(-4) ) (6400xx 10^(3) )^(3) )/( (4pi xx 10^(-7) )`
`therefore m= 1.048 xx 10^(23) Am^(2) (= "ampere" xx "metre"^(2) )`