Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction. The force per unit length in N/m of one wire on the other is:
A. 1 × 10−3, repulsive
B. 1 × 10−3, attractive
C. 4 × 10−5, repulsive
D. 4 × 10−5, attractive
E. none of these