Two Long,parallel Wires Are Spaced 1 M Apart in Air,and $\pi\mu$

Multiple Choice

Two long,parallel wires are spaced 1 m apart in air,and you have established a current of 1 A in each.The force per unit length that each wire exerts on the other is

A) 4 $\pi\mu$ ₀
B) 2 $\pi\mu$ ₀
C) $\mu$ ₀
D) $\mu$ ₀/4 $\pi$
E) $\mu$ ₀/2 $\pi$