Two long parallel wires, AB and CD, carry equal currents in opposite directions. They lie in the x-y plane, parallel to the x-axis, and pass through the points (0,-a,0) and (0,a,0) respectively, Figure. The resultant magnetic field is:

Options

A. zero on the x-axis
B. maximum on the x-axis.
C. direction along the z-axis at the origin, but not at other point on the z-axis.
D. directed along the z-axis at all points on the z-axis.

Answer

B, D

Explanation

From the diagram it is clear the correct choices are b and d.