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) $300$
With opposite currents, the two fields at the midpoint point the same way and add. Each wire is $4$ cm away:
$$B = 2 \times \frac{\mu_0I}{2\pi d} = 2 \times \frac{2 \times 10^{-7} \times 30}{0.04} = 3 \times 10^{-4}\ \text{T} = 300\ \mu\text{T}$$
Solution by Sreeraj P, M.Sc Physics