The magnetic field at a distance 'r' from a long straight wire carrying current I is 0.4 tesla. The magnetic field at a distance 2r will be

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The magnetic field due to a long straight wire carrying current I at a distance r is given by B = ₀ I 2 r . This implies that B 1 r . Let the magnetic field at distance r be B₁ = 0.4 T. At distance 2r , the magnetic field B₂ will be: B₂ B₁ = r 2r = 1 2 B₂ = B₁ 2 = 0.4 2 = 0.2 T. Answer: 0 2 tesla