Q 12-04-022NEETJEE MainEasy
Two long straight parallel wires are $5$ cm apart and carry currents of $10$ A and $20$ A in the same direction. The force per metre length between them is
Answer: (C) $8 \times 10^{-4}$ N, attractive
$\dfrac{F}{L} = \dfrac{\mu_0 I_1 I_2}{2\pi d} = \dfrac{2 \times 10^{-7} \times 10 \times 20}{0.05} = 8 \times 10^{-4}$ N/m.
Currents in the same direction attract.
Solution by Sreeraj P, M.Sc Physics