Two infinitely long parallel wires separated by distance d carry currents I₁ and I₂ in the same direction. What is the force per unit length between them?
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Two infinitely long parallel wires separated by distance d carry currents I₁ and I₂ in the same direction. What is the force per unit length between them?

G1 Physics · Accepted Answer

Each wire lies in the field μ₀I/(2πd) of the other. Same-direction currents attract.