Question

Two long parallel wires are at a distance of 1m. If both of them carry one ampere of current in same direction, then the force of attraction on unit length of the wires will be

• A. $2\times {10}^{-7}N/m$
• B. $4\times {10}^{-7}N/m$
• C. $8\times {10}^{-7}N/m$
• D. ${10}^{-7}N/m$

Answer 1

The correct option is A $2\times {10}^{-7}N/m$

Given: $I_1=I_2=1$ A

Distance between the wires, $d=1$ m

Force of attraction per unit length, $f=\frac{{\mu }_0{I}_1{I}_2}{2\pi d}$ $N/m$

$\therefore$ $f=\frac{4\pi \times {10}^{-7}\times \left(1\right)\left(1\right)}{2\pi \times 1}=2\times {10}^{-7}$ $N/m$