Two infinite straight current-carrying wires are 6 cm apart. The left wire carries 5 A upward and the right wire carries 4 A downward. Point O is 4 cm to the right of the 4 A wire. The magnitude of the net magnetic field at O is:
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Question

Two infinite straight current-carrying wires are 6 cm apart. The left wire carries 5 A upward and the right wire carries 4 A downward. Point O is 4 cm to the right of the 4 A wire. The magnitude of the net magnetic field at O is:

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G1 Physics · Accepted Answer

O is 10 cm from the 5 A wire and 4 cm from the 4 A wire. Their fields at O oppose. B n e t = ∣ μ 0 5 / ( 2 π × 0.10 ) − μ 0 4 / ( 2 π × 0.04 ) ∣ = 1 × 10 − 5 B_net=|μ₀5/(2π×0.10)-μ₀4/(2π×0.04)|=1×10⁻⁵ B n ​ e t = ∣ μ 0 ​ 5/ ( 2 π × 0.10 ) − μ 0 ​ 4/ ( 2 π × 0.04 ) ∣ = 1 × 1 0 − 5 T.