A straight conductor carriers a current alon the `z`-axis Consider the points `A(a,0,0),B(0,-a,0),C(-a,0,0)` and `D(0,a,0)`
(i) All four points have magnetic fields of the same magnitude.
(ii) All four points have magnetic fields of the different direction.
(iii) The magnetic fields at `A` and `C` are in opposite directions
(iv) The magnetic fields at `A` and `B` are mutually perpendicular

Options

A. (i),(ii)
B. (ii),(iii)
C. (i),(ii)
D. all

Answer

D

Explanation

`|vec(B)_(A)|=|vec(B)_(B)|=|vec(B)_(C)|=|vec(B)_(C)|=(mu_(0)I)/(2pia)`