Question

The earth’s magnetic field lines resemble that of a dipole at the centre of the earth. If the magnetic moment of this dipole is close to $8\times 10^{22}A{m}^2$, the value of earth’s magnetic field near the equator is close to (radius of the earth = $6.4\times 10^6$ m)

• A. 0.6 Gauss
• B. 1.2Gauss
• C. 1.8 Gauss
• D. 0.32 Gauss

Answer 1

Answer: (A)

Given $M=8\times 10^{22}A{m}^2$
$d=R_e=6.4\times 10^{6}m$
Earth’s magnetic field, $B=\frac{{\mu }_0}{4\pi }.\frac{2M}{d^3}$
$=\frac{4\pi \times 10^{-7}}{4\pi }\times \frac{2\times 8\times 10^{22}}{{\left(6.4\times 10^6\right)}^3}$
$\cong$ 0.6 Gauss