Q. 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 distances of $x$ and $y$ from the centre of the magnet is
A) $2^{- 3}$
B) $2^{- 1/3}$
C) $2^{3}$
D) $2^{1/3}$
Explanation
(d) $B_{1} = \frac{2M}{x^{3}}$ and $B_{2} = \frac{M}{y^{3}}$
As $B_{1} = B_{2}$
Hence $\frac{2M}{x^{3}} = \frac{M}{y^{3}}$ or $\frac{x^{3}}{y^{3}} = 2$ or $\frac{x}{y} = 2^{1/3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.