Q 12-04-037JEE MainJEE Main 2026 (6 Apr, Shift 2)Easy
A current of $30$ A each flows in opposite directions in two conducting wires, placed parallel to each other at a distance of $8$ cm. The magnetic field at the mid point between the two wires is ______ $\mu$T. ($\dfrac{\mu_0}{4\pi} = 10^{-7}\ \text{N/A}^2$)
Answer: (B) $300$
Concept. Straight wire: $B=\dfrac{\mu_0I}{2\pi r}$. Opposite currents give fields in the same direction between the wires, so they add.
Step 1. Each. $\dfrac{2\times10^{-7}\times30}{0.04}=1.5\times10^{-4}$ T.
Step 2. Total. $3\times10^{-4}$ T $=300\ \mu$T.
Answer. Option B.
Solution by Sreeraj P, M.Sc Physics
