Question

Two very long, straight, parallel conductors $A$ and $B$ carry current of $5 A$ and $10 A$ respectively and are at a distance of $10 cm$ from each other. The direction of current in two conductors is same. The force acting per unit length between two conductors is: $\left(\mu_0=4 \pi \times 10^{-7}\right.$ SI unit $)$

• A. $2 \times 10^{-4}\, Nm ^{-1}$ and is attractive
• B. $2 \times 10^{-4}\, Nm ^{-1}$ and is repulsive
• C. $1 \times 10^{-4} \,Nm ^{-1}$ and is attractive
• D. $1 \times 10^{-4}\, Nm ^{-1}$ and is repulsive

Answer 1

Answer: (C)

$\frac{ F _{ M }}{\ell}=\frac{\mu_0 i _1 i _2}{2 \pi r }$
$=\frac{4 \pi \times 10^{-7} \times 5 \times 10}{2 \pi \times 0.1}=10^{-4} \,N / m$