Q.
A bar magnet of length 3 cm has a point $A$ and $B$ along axis at a distance of 24 cm and 48 cm on the opposite ends. Ratio of magnetic fields at these points will be
A) 8
B) 3
C) 4
D) $1/2\sqrt{2}$
Explanation
(a) Here, $2l = 3\ cm;d_{1} = 24\ cm,\ d_{2} = 48\ cm$.
As the magnet is short, $\frac{B_{1}}{B_{2}} = \frac{d_{2}^{3}}{d_{1}^{3}} = \left( \ \frac{48\ cm}{24\ cm} \right)^{3} = 8$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.