AIIMS 2018 Physics Magnetic Field due to Current MCQ Question

To find the magnetic field intensity at the midpoint between two long parallel wires carrying equal currents in opposite directions, we use the formula for the magnetic field due to a long straight wire: $B = \frac{{\mu_0 I}}{{2\pi r}}$. Here, $\mu_0 = 4\pi \times 10^{-7} \, \text{T m/A}$, $I = 2 \, \text{A}$, and $r = 1 \, \text{m}$ (the distance from each wire to the midpoint). Calculating gives $B = \frac{{4\pi \times 10^{-7} \times 2}}{{2\pi \times 1}} = 4 \times 10^{-7} \, \text{T}$ from each wire, but since the currents are in opposite directions, the fields at the midpoint add up, resulting in $8 \times 10^{-7} \, \text{T}$.

Other options are incorrect because they do not account for the additive nature of the magnetic fields from both wires at the midpoint, leading to an underestimation of the total magnetic field intensity.