Q. Two like magnetic poles of strength 10 and 45 SI units are separated by a distance $30\ cm$. The intensity of magnetic field is zero on the line joining them
A) At a point $10\ cm$ from the stronger pole
B) At a point $20\ cm$ from the stronger pole
C) At the mid-point
D) At infinity
Explanation
(b) Suppose magnetic field is zero at point $P$ which lies at a distance $x$ from 10 unit pole. Hence at $P$
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$\frac{\mu_{0}}{4\pi}.\frac{10}{x^{2}} = \frac{\mu_{0}}{4\pi}.\frac{40}{(30 - x)^{2}} \Rightarrow x = 10cm$
So from stronger pole distance is $20\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.