The problem statement, all variables and given/known data Two negative charges repel each other. Two parallel wires with current going in the same direction attract each other. Yet if one walks with the moving charge in the wires, the charges appear stationary and should repel each other - explain why if you are stationary with respect to the wire, they would attract while if you move with the charge they should repel." The attempt at a solution This is more of a conceptual question, so I really don't know how to approach it. Any help would be appreciated. I don't think the equations are relevant, but there's Coulomb's Law for static charges and the fact that currents going in the same direction in parallel wires attract, but I don't know how to resolve the issue of different frames of reference, i.e. the charges are stationary wrt the observer or the charges are moving wrt the observer and how this affects the force perceived.