From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is :
(A)a linearly decreasing function of distance upto the boundary of the wire and then a linearly increasing one for the outside region.
(B)uniform and remains constant for both the regions.
(C)a linearly increasing function of distance upto the boundary of the wire and then linearly decreasing for the outside region.

(D)a linearly increasing function of distance `` r `` upto the boundary of the wire and then decreasing one with `` 1 / r `` dependence for the outside region.