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The force existing between two parallel current carrying conductors is F. If the current in each conductor is halved, then the value of the force will be ______.

Asked in GUJCET 2013 · Force between parallel currents

Answer: (3) F/4

Step-by-step solution

Given: two long parallel conductors a fixed distance d apart carry currents I₁ and I₂, and the force between them is F.

Idea: each wire sits in the other's field, and the force per unit length is F/ℓ=(μ₀I₁I₂)/(2π d) — proportional to the product of the currents.

Halving each current: the product becomes (I₁)/2×(I₂)/2=(I₁I₂)/4.

The separation and the lengths are unchanged, so nothing else in the expression moves.

So the new force is F/4.

Why the other options are wrong

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