Question

If $B_E$ represents equatorial magnetic field and $B_A$ represents axial magnetic field due to a bar magnet.
Which of the following relationships between $B_E$ and $B_A$ is correct?

• A. $B_E=2B_A$
• B. $B_A=2B_E$
• C. $B_E=4B_A$
• D. $B_A=4B_E$

Answer 1

Answer: (B)

As equatorial magnetic field due to bar magnet is
$B_E=\frac{{\mu }_{0}m}{4\pi r^3}...\left(i\right)$
and axial magnetic field due to bar magnet is
$B_A=\frac{{\mu }_0}{4\pi }\frac{2m}{r^3}...\left(ii\right)$
From $\left(i\right)$ and $\left(ii\right)$, we get
$B_A=2B_E$