As shown in the figure, two infinitely long straight parallel wires \(P\) and \(Q\) carrying equal currents in opposite directions are arranged parallel to \(\mathrm{Y}\)-axis. If the magnetic field due to wire \(\mathrm{P}\) at the origin ' \(\mathrm{O}\) ' of the co-ordinate system is B, then match the resultant magnetic fields at various points given in column \(A\) with the points given in column \(B\).
\(\begin{array}{ll}
\text{Column A} & \text{Column B} \\
\text{A)} \frac{B}{4} & \text{i)} (0,0) \\
\text{B)} \frac{B}{2} & \text{ii)} (a, 0) \\
\text{C)} \frac{2 \mathrm{~B}}{3} & \text{iii)} (2a, 0) \\
\text{D)} 2 \mathrm{~B} & \text{iv)} (3 \mathrm{a}, 0) \\
\end{array}\)


The correct answer is

1. A \(\begin{array}{llll}\text { A } & \text { B } & \text { C } & \text { D } \\ \text { ii } & \text { iii } & \text { iv } & \text { i }\end{array}\)
2. B \(\begin{array}{llll}\text { A } & \text { B } & \text { C } & \text { D } \\ \text { iv } & \text { ii } & \text { iii } & \text { i }\end{array}\)
3. C \(\begin{array}{llll}\text { A } & \text { B } & \text { C } & \text { D } \\ \text { i } & \text { iii } & \text { ii } & \text { iv }\end{array}\)
4. D \(\begin{array}{cccc}\text { A } & \text { B } & \text { C } & \text { D } \\ \text { iii } & \text { ii } & \text { i } & \text { iv }\end{array}\)