Question

Two small bar magnets are placed in a line at certain distance $d$ part. If the length of each magnet is negligible compared to $d$, the force between them will be inversely proportional to:

• A. $d^2$
• B. $d$
• C. $d^3$
• D. $d^4$

Answer 1

The correct option is D $d^4$

For bar magnet $F=\frac{{\mu }_0}{4\pi }\left(\frac{6M{M}^{\prime }}{d^4}\right)$ in axial position.

$⟹F\alpha \frac{1}{d^4}$