Consider two long parallel wires which are perpendicular to the plane of the paper (i.e., the x-y plane). Both wires carry the same current, I. Which of the following statements is true about the interaction between the wires?
a) The wires attract each other.
b) The wires repel each other.
c) The wires exert no force on each other.
d) The direction of the force depends on the direction of the current.