Question
Two thin long parallel wires separated by a distance $b$ are carrying a current $i$ $amp$ each. The magnitude of the force per unit length exerted by one wire on the other is
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Answer
(b) Force per unit length $ = \frac{{{\mu _0}}}{{4\pi }}.\frac{{2{i_1}{i_2}}}{r} = \frac{{{\mu _0}}}{{2\pi }}.\frac{{{i^2}}}{b}$
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