Question
In figure two parallel infinitely long current carrying wires are shown. If resultant magnetic field at point $A$ is zero. Then determine current $I.$ (in $A$)
✓
Answer
Consider the following figure
At point $A$
$B _{1}= B _{2}$
$\frac{\mu_{0} i _{1}}{2 \pi r _{1}}=\frac{\mu_{0} i _{2}}{2 \pi r _{2}}$
$\frac{ i _{1}}{29}=\frac{10}{9}$
$i _{1}=30 A$
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