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5.Magnetism and Matter
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Two like magnetic poles of strength $ 10$ and $40$ $ 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
Solution
(b)Suppose magnetic field is zero at point $ P.$ Which lies at a distance $x$ from $10$ unit pole. Hence at $P$
$\frac{{{\mu _0}}}{{4\pi }}.\frac{{10}}{{{x^2}}} = \frac{{{\mu _0}}}{{4\pi }}.\frac{{40}}{{{{\left( {30 – x} \right)}^2}}} \Rightarrow x = 10\,cm$
So from stronger pole distance is $20\, cm.$
Standard 12
Physics
