An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current $I$ along the same direction is shown in Figure. Magnitude of force per unit length on the middle wire $B$ is given by

• A

  $\frac{{\mu }_0{I}^2}{2\pi d}$
• B

  $\frac{2{\mu }_0{I}^2}{\pi d}$
• C

  $\frac{\sqrt{2}{\mu }_0{I}^2}{\pi d}$
• Correct answer
  D

  $\frac{{\mu }_0{I}^2}{\sqrt{2}\pi d}$

Hence, the correct answer is option: 'D'.