Question

Two parallel wires carrying currents $I_1$ and $I_2$ in opposite directions and separated by a distance $d$ experience a :

• A. Replusive force ${\mu }_0{I}_1{I}_2/2\pi d$
• B. Attractive force ${\mu }_0{I}_1{I}_2/2\pi d$
• C. Repulsive force ${\mu }_0{I}_1{I}_2/2\pi d^2$
• D. Attractive force ${\mu }_0{I}_1{I}_2/2\pi d^2$

Answer 1

The correct option is A Replusive force ${\mu }_0{I}_1{I}_2/2\pi d$

The magnetic filed at wire-2 due to current carrying wire-1 is given by,

$B_1=\frac{{\mu }_0{I}_1}{2\pi d}$.

Force experienced by wire-2 due to $B_1$ per unit length is,

$F_l=B_1{I}_2=\frac{{\mu }_0{I}_1{I}_2}{2\pi d}$

as the direction of currents are opposite, the force is repulsive force.