Question

A magnetic dipole of magnetic moment 1.44 A $m^2$ is placed horizontally with the north pole pointing towards north. Find the position of the neutral point if the horizontal component of the earth's magnetic field is $18\mu T$.

Answer 1

We know for a magnetic dipole with its pole pointing to the north, the neutral point in the broadside on position.

Again $\overrightarrow{B}$ in this case $\frac{{\mu }_{0}M}{4\pi d^3}$

= ${\overrightarrow{B}}_H$ due to earth

$\Rightarrow \frac{{10}^{-7}\times 1.44}{d^3}=18\times {10}^{-6}$

$\Rightarrow d_3=8\times {10}^{-3}$

$d=2\times {10}^{-1}$ = 20 cm

in the plane bisecting the dipole.