The magnitude of the axial field due to a short bar magnet at a distance of $50 \mathrm{~cm}$ from its…
The magnitude of the axial field due to a short bar magnet at a distance of $50 \mathrm{~cm}$ from its mid-point is (The magnetic moment of the bar magnet is $0.4 \mathrm{Am}^2$ )
$3.2 \times 10^{-7} \mathrm{~T}$
$1.6 \times 10^{-7} \mathrm{~T}$
$6.4 \times 10^{-7} \mathrm{~T}$
$4.8 \times 10^{-7} \mathrm{~T}$
Solution
Magnetic moment, $\mathrm{m}=0.4 \mathrm{Am}^2$
Distance, $\mathrm{r}=50 \mathrm{~cm}=0.5 \mathrm{~m}$
The magnitude of the axial field
$\begin{aligned}
& \text { Baxial }=\frac{\mu_0}{4 \pi}\left(\frac{2 \mathrm{~m}}{\mathrm{r}^3}\right) \\
& =\left(10^{-7}\right) \times \frac{2 \times 0.4}{(0.5)^3}=6.4 \times 10^{-7} \mathrm{~T}
\end{aligned}$