JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Magnetic Effects of Current

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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 ______

μ T

(\frac{μ _{0}}{4 π} = 1 0^{- 7} N / A^{2})

(A)30
(B)300✓ Correct
(C)150
(D)0.1

Answer: (B)

Solution

Currents in opposite directions produce fields that point the same way midway between the wires, so they add:

B = 2 \cdot \frac{μ _{0} I}{2 π r} = \frac{μ _{0} I}{π r}

, with

r = 4 \times 1 0^{- 2} m

. Then

B = \frac{4 π \times 1 0 ^{- 7} \times 30}{π \times 4 \times 1 0 ^{- 2}} = 3 \times 1 0^{- 4} T = 300 μ T

JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Single correct option

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