The magnetic field of a planet at any location is approximately 0.5 G. Estimate its dipole moment if its position from the centre is $25.6 \times 10^6 M$. Assume the planet to be of spherical shape:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → $8.39 \times 10^{24} Am^2$
The equitorial magnetic field is -
$B=\frac{μ_0}{4π}\frac{M}{r^3}$
where,
B, Magnetic field = $0.5G=0.5×10^{-4}T$
$r$, radius from center of planet = $25.6×10^6m$
$M=\frac{Br^3}{\frac{μ_0}{4π}}=\frac{(0.5×10^{-4})×(25.6×10^6)^3}{2×10^{-7}}$
$≃8.39×10^{24}Am^2$