For electric forces we say that "likes repel, unlikes attract," but for the magnetic forces between two parallel current-carrying wires, we can say "likes attract, unlikes repel." to get a feel for the size of the effects, calculate the magnitude of the force per meter (that is, the force on one meter of wire) if i1= i2 = 12 amperes, and the distance between the wires is d = 4 centimeter.