Four wires carrying current I₁ = 2A, I₂ = 4A, I₃ = 6A and I₄ = 8A respectively cut the page perpendicularly as shown in figure. The value of . ∫B d for the loop shown would be :-

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G1 Physics · Accepted Answer

Ampere's law gives ∮B⃗·dℓ⃗=μ₀I enclosed with algebraic current according to the loop direction. From the figure the signed enclosed current is -2 A. Thus the integral is -2μ₀ Wb/m, option B.