Question

The magnetic field at a point $x$ on the axis of a small bar magnet is equal to the field at a point $y$ on the equator of the same magnet. The ratio of the distance of $x$ and $y$ from the centre of the magnet is?

• A. $2^{-3}$
• B. $2^{-1/3}$
• C. $2^3$
• D. $2^{1/3}$

Answer 1

The correct option is D $2^{1/3}$

As we know that,

On the axis, $B_1=\frac{2M}{x^3}$ On the equator, $B_2=\frac{M}{y^3}$

as $B_1=B_2$

$\frac{2M}{x^3}=\frac{M}{y^3}$

∴ $(\frac{x}{y}{)}^3=2$

$\frac{x}{y}=2^{\left(1/3\right)}$