GATE 2023 IN – Question 27
The force per unit length between two infinitely long parallel conductors, with a gap of 2 cm between them is 10 µN/m. When the gap is doubled, the force per unit length will be __________ µN/m (rounded off to one decimal place).
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Correct answer: 4.9 to 5.1
Explanation
For fixed currents, $F/\ell=\mu I_1I_2/(2\pi d)$. Doubling separation halves the force: $10/2=\boxed{5.0}$ μN/m.