Two parallel wires carrying equal currents in opposite  directions are placed at x = ±a parallel to y-axis with z = 0. Magnetic field at origin O is B1 and at P (2a, 0, 0) is B2. Then the ratio B1/B2 is

Case I: If the currents are in the directions shown in figure, then B→1 =−2 μ02π  iak^=−μ0πa k^=magnetic  field at OB→2 =μ02π  iak^−μ02π i3a k^=magnetic  field at P=  μ03π  iak^∴    B1/B2 = 3Case II: In this case,B→1=  μ0iπa  k^and    B→2 = μ0i3πa  iak^∴    B1B2 = 3