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. $B_E = 2\,B_A$
• B. $B_A = 2\,B_E$
• C. $B_E = 4\,B_A$
• D. $B_A = 4\,B_E$

Answer 1

Answer: (B)

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