Question

Two long parallel conductors are placed at right angles to a metre scale at the $2cm$ and $6cm$ marks as shown in the figure

They carry currents of $1A$ and $3A$ respectively. They will produce zero magnetic field at (ignore earth's magnetic field)

• A. $5 \, cmmark$
• B. $3 \, cmmark$
• C. $1 \, cmmark$
• D. $8 \, cmmark$

Answer 1

Answer: (B)

Here, $x$ is the distance from the $2 \, \text{cm}$ mark.
$\frac{\left(\mu \right)_{o} I_{1}}{2 \pi \, x}=\frac{\left(\mu \right)_{o} I_{2}}{2 \pi \left(\right. 4 - x \left.\right)} \, \\ \, \, \left(\right. 4 - x \left.\right)\times 1=x\times 3 \\ \, \, 4-x=3x \\ \, 4=4x\Rightarrow x=1$