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Asked in RS Academy GUJCET booklet · Force between parallel currents
Given: two long parallel wires a fixed distance apart, each carrying 2 A in the same direction, with force F between them.
Idea: the force per unit length is (μ₀I₁I₂)/(2π d). Its size goes with the product of the currents; its sense depends only on whether the currents are parallel or antiparallel.
New currents: the product falls from 2×2=4 to 1×1=1, so the force falls to 1/4 of F.
Reversing both currents reverses each wire's field and each wire's current together, so the direction of the force is unchanged.
The wires still carry their currents the same way as each other, and parallel currents attract: the force is F/4 and attractive.
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