Two very long straight parallel wires, parallel to y-axis, carry currents 41 and I, along+y direction and-y direaction respectively. The wires are passes through the x-axis at the points `(d, 0,0)` and `(-d, 0,0)` respectively. The graph of magnetic field z-component as one moves along the x-axis from `x = - d` to `x = +d`, is best given by

Options

A.
B.
C.
D.

Answer

C

Explanation

Field due to wires
`B_(1)+(mu_(0)(4I))/(2pi(d-x))`
`B_(2)=(mu_(0)(I))/(2pi(d+x))`
`B_("Net")=(mu_(0)I)/(2pi)[4/(d-x)+1/(d+x)]`
`implies ` Value of `Bto oo` as `x to -d` or `x to -d`

`implies` B along +z `implies` B is minimum when point near to wires 2