Page:Electricity (1912) Kapp.djvu/145



have seen that two carriers of static charges, if brought near each other, act upon each other with a certain mechanical force. The same is the case with conductors carrying moving charges, that is to say, electric currents under certain conditions. The two conductors must lie near each other and run more or less parallel. If the two currents flow in the same direction the wires attract each other, if they flow in opposite directions the wires repel each other. The fact that parallel currents flowing in the same direction attract each other may be proved by a very simple experiment: Take a loosely coiled hank of fine, and therefore very flexible, cotton-covered copper wire, hang it over a bar, and send a current through it. Immediately on closing the switch, which completes the circuit through the hank of wire and allows the current to flow, we shall observe a tightening up of the