An arrangment of three parallel staright wires placed perpendcular 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

Options

A. `(2mu_(0)i^(2))/(pid)`
B. `(sqrt(2)mu_(0)i^(2))/(pid)`
C. `(mu_(0)i^(2))/(sqrt(2)pid)`
D. `(mu_(0)i^(2))/(2pid)`

Answer

C

Explanation

Force on `B`

`F'=sqrt(2). (mu_(0)i^(2))/(2pid)=(mu_(0)i^(2))/(sqrt(2)pid)`