Q. The points $A\ and\ B$ are situated perpendicular to the axis of 2 cm long bar magnet at large distances $x$ and 3$x$ from the centre on opposite sides. The ratio of magnetic fields at $A\ and\ B$ will be approximately equal to
A) 27 : 1
B) 1 : 27
C) 9 : 1
D) 1 : 9
Explanation
(a) On equatorial line, magnetic field due to magnet varies inversely as cube of the distance, therefore,
$\frac{B_{1}}{B_{2}} = \left( \frac{3x}{x} \right)^{3} = 27\ :1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.