5.Magnetism and Matter
medium

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

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